Systematics and phylogeny of Potamotrygonocestus - IB-USP

Systematics and phylogeny of Potamotrygonocestus (Platyhelminthes, Tetraphyllidea, Onchobothriidae) with descriptions of three new species from freshwater potamotrygonids (Myliobatoidei, Potamotrygonidae) lackwell Publishing, Ltd

FERNANDO P. L. MARQUES, DANIEL R. BROOKS & MARIA L. G. ARAÚJO

Accepted: 19 June 2002

Marques, F. P. L., Brooks, D. R. & Araújo, M. L. G. (2003). Systematics and phylogeny of Potamotrygonocestus (Platyhelminthes, Tetraphyllidea, Onchobothriidae) with descriptions of three new species from freshwater potamotrygonids (Myliobatoidei, Potamotrygonidae). — Zoologica Scripta, 32, 367– 396. Specimens of Potamotrygonocestus used in the present taxonomic and phylogenetic study were collected in freshwater potamotrygonids from the Rio Paraná (Puerto Reconquista, Santa Fé, Argentina; 59°42′W, 29°29′S) during February 1995, and from the Amazon region of Brazil during September to December 1996, supplemented by specimens previously deposited in museum collections. Six species of Potamotrygonocestus were recognized (P. amazonensis, P. chaoi sp. n., P. fitzgeraldae sp. n., P. magdalenensis, P. maurae sp. n., P. travassosi ), for which an identification key is provided. Potamotrygonocestus orinocoensis is considered a junior synonym of P. travassosi. Additional specimens of Potamotrygonocestus may represent two undescribed species. A phylogenetic analysis of six morphological characters for the six named species of Potamotrygonocestus generated a single tree eight steps long, with a consistency index of 0.87, a retention index of 0.90, and a rescaled consistency index of 0.79 with the following topology: (P. maurae sp. n. ((P. amazonensis + P. magdalenensis) (P. chaoi sp. n. (P. fitzgeraldae sp. n. + P. travassosi )))). Fernando P. L. Marques, Department of Zoology, University of Toronto, Toronto, Ontario M5S 3G5, Canada., Present address: Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, Caixa Postal 11461 — São Paulo/SP 05422-970, Brazil. E-mail: [email protected], Daniel R. Brooks, Department of Zoology, University of Toronto, Toronto, Ontario M5S 3G5, Canada, Maria L. G. Araújo, Laboratório de Histologia, Universidade do Amazonas, Av. Gen. Rodrigo Otávio Jordão, 3000, Manaus AM 69000–000, Brazil

Introduction The genus Potamotrygonocestus was first established for P. magdalenensis Brooks & Thorson, 1976, found in the endemic freshwater potamotrygonid Potamotrygon magdalenae (Valenciennes, 1865) from Rio Magdalena in Colombia. Rego (1979) described Potamotrygonocestus travassosi in Potamotrygon orbignyi (Castelnau, 1855) from Rio Amazonas, Maicurú, Pará, Brazil. Subsequently, Potamotrygonocestus amazonensis Mayes, Brooks Thorson, 1981 was described in Potamotrygon constellata ( Vaillant, 1880) from the Upper Solimões Basin, Atalaia do Norte, Amazonas, Brazil. Brooks et al. (1981) provided the first systematic review of cestodes inhabiting freshwater potamotrygonids in which they described Potamotrygonocestus orinocoensis inhabiting Potamotrygon orbignyi from the delta of Rio Orinoco in Venezuela. In their review, Brooks et al. (1981) considered Potamotrygonocestus travassosi to be species inquirenda, as Rego (1979) clearly mistook a proglottis of the

© The Norwegian Academy of Science and Letters • Zoologica Scripta, 32, 4, July 2003, pp367– 396

trypanorhynch eucestode Paroncomegas araya ( Woodland, 1934) Campbell et al., 1999 for one of Potamotrygonocestus travassosi in the original description. Hence, they recognized three diagnosable species within the genus for which they also proposed a phylogenetic hypothesis. In their phylogenetic analysis, Brooks et al. (1981) suggested a close affinity among Potamotrygonocestus, Pachybothrium Baer & Euzet, 1962 and Pedibothrium Linton, 1909, and used the latter two taxa as outgroups. In this study, we provide a taxonomic review of the genus Potamotrygonocestus based on specimens collected by one of the authors and material from museum collections. Following this, we provide additional justification for the use of Pachybothrium and Pedibothrium as outgroups, and develop a new phylogenetic hypothesis for the recognized species of Potamotrygonocestus. Finally, we briefly discuss the historical association between Potamotrygonocestus, Pachybothrium and Pedibothrium and their hosts. 367

Systematics and phylogeny of Potamotrygonocestus • F. P. L. Marques et al.

Table 1 List of the hosts for parasites examined during the present study. Numbers following UFPB refer to the accession numbers for hosts

deposited at the Universidade Federal da Paraíba, João Pessoa, Paraíba, Brazil. Species

Localities sampled

Paratrygon aiereba

Cachoeira do Ariri, Ilha de Marajó, Pará, Brazil [two males (UFPB 3478) and one female (UFPB 3479)]; Rio Tocantins, Marabá, Pará, Brazil (one female); Rio Negro, Barcelos, Amazonas, Brazil (three females); Rio Negro, Ilha Guariba, Amazonas, Brazil [one male and two females (UFPB 3533–3535)]

Plesiotrygon iwamae Potamotrygon constellata

Confluence of Paraná Janauacá and Rio Solimões, near Manaus, Amazonas, Brazil [one male (UFPB 3540)] Cachoeira do Ariri, Ilha de Marajó, Pará, Brazil [11 males (UFPB 3472, 3483, 3518, 3519, 3527, 3529) and 13 females (UFPB 3470, 3473– 3475, 3525, 3526, 3528, 3530)]; Cametá, confluence of Rio Tocantins and Rio Solimões, Cametá, Pará, Brazil (one male), Paraná Janauacá and Rio Solimões, near Manaus, Amazonas, Brazil (one female) Rio Apa, Bela Vista, Mato Grosso do Sul, Brazil (one male and one?) Rio Tocantins, Marabá, Pará, Brazil (five females) Rio Xingú, Altamira, Pará, Brazil (four males and six females) Cachoeira do Ariri, Ilha de Marajó, Pará, Brazil [five males and eight females (UFPB 3467)]; Cametá, confluence of Rio Tocantins and Rio Solimões, Cametá, Pará, Brazil [one male (UFPB 3522)]; Paraná Janauacá and Rio Solimões, near Manaus, Amazonas Brazil [one male (UFPB 3541) and two females]; Rio Tocantins, Marabá, Pará, Brazil (one male); Iguarapé Corinbaú, Rio Branco, Amazonas, Brazil (one male); Rio Negro, Ilha Guariba, near Barcelos, Amazonas, Brazil (one female); Rio Arirara, Upper Rio Negro, near Barcelos, Amazonas, Brazil (one male); Rio Paraná, Puerto Reconquista, Santa Fé, Argentina [six males and four females (UFBP 3053–3055)] Cachoeira do Ariri, Ilha de Marajó, Pará, Brazil [one male and one female (UFPB 34671)] Cachoeira do Ariri, Ilha de Marajó, Pará, Brazil [nine males (UFPB 3469, 3476, 3480–3482, 3515, 3517, 3520, 3531) and two females (UFPB 3468, 3516)]; Cameta, confluence of Rio Tocantins and Rio Solimões, Cametá, Pará, Brazil [one female (UFPB 3521) and unidentified specimen (UFPB 3523)]; Paraná Janauacá and Rio Solimões, near Manaus, Amazonas, Brazil (one male); Rio Tocantins, Marabá, Pará, Brazil (two females); Rio Branco, Amazonas, Brazil [one female (UFPB 3536)]; Rio Negro, Ilha Guariba, near Barcelos, Amazonas, Brazil [one male (UFPB 3537)]; Rio Arirara, Upper Rio Negro, near Barcelos, Amazonas, Brazil [one male and five females (UFPB 3538–3539)]; Rio Arirara, Upper Rio Negro, near Barcelos, Amazonas, Brazil [one male and five females (UFPB 3538–3539)] Ilha do Catalão, confluence of Rio Negro and Rio Solimões, near Manaus, Amazonas, Brazil (one male) Rio Guamá, Ourém, Pará, Brazil (UFPB 3532); Paraná Janauacá and Rio Solimões near Manaus, Amazonas, Brazil [one female (UFPB 3542)] Confluence of Rio Poty and Rio Parnaíba, Teresina, Piauí, Brazil (three males and three females) (some specimens are deposited at UFPB) Rio Negro, Barcelos, Amazonas, Brazil [five males (UFPB 3543) and five females]

P. falkneri P. henlei P. leopoldi P. motoro

P. ocellata P. orbignyi

P. schroederi P. scobina P. signata Potamotrygon sp.

Materials and methods Specimens of freshwater potamotrygonids were collected, using long-lines, from Rio Paraná (Puerto Reconquista, Santa Fé, Argentina; 59°42′ W, 29°29′ S) during February 1995, and from the Amazon region of Brazil during September to December 1996. Live specimens and the majority of loose proglottides were removed from the spiral valve in situ, placed in freshwater, fixed with hot alcohol/formalin/acetic acid (AFA), and transferred to cool fixative. After 24 h, the worms were transferred to 70% ethanol for storage. Given the small size of the specimens of Potamotrygonocestus, most of the cestodes were collected in the laboratory from the spiral valves that had been fixed in the field in warm 10% formalin. A list of hosts examined in the present study is provided in Table 1. Whole mounts of all eucestodes were stained with acetocarmine or Mayer’s haematoxylin, dehydrated in ethanol, cleared in methyl salicylate, and mounted in Canada balsam. Serial transverse sections of specimens in paraffin were cut at 8 µm intervals and stained with haematoxylin and eosin. Measurements were obtained using an OPTIMAS image analysis system attached to a BH-2 Olympus microscope. Measurements are given as range followed in parentheses by mean, standard deviation and sample size. For measurements of sample size equal to two, only the range is provided. All measurements are 368

in µm unless otherwise stated. Figures were drawn with the aid of a drawing tube on a BX-50 or BH-2 Olympus microscope. Additional specimens were obtained from the following parasite collections: Coleção Helmintológica do Instituto Oswaldo Cruz, Rio de Janeiro, Brazil (CHIOC); US National Parasite Collection, Biosystematics and National Parasite Collection Unit, USDA, Agricultural Research Service, Beltsville, MD, USA (USNPC); and Harold W. Manter Laboratory, University of Nebraska, Lincoln, NB, USA (HWML). Types, paratypes and voutcher specimens have been deposited at the Coleção Helmintológica do Museu de Zoologia da Universidade de São Paulo, SP, Brazil (CHMZUSP). Material examined Potamotrygonocestus amazonensis Brooks, Mayes & Thorson, 1981: USNPC 76363 (holotype), HWML 21019 (six paratypes), four specimens from Rio Paraguay, Corumbá, Mato Grosso, Brazil in Potamotrygon motoro, one specimen from Rio Apa, Paraguay Basin, Bela Vista, Mato Grosso do Sul, Brazil in P. falkneri, two specimens from Lower Amazon, Belém, Pará, Brazil in P. constellata, one specimen from Lower Amazon, Belém, Pará, Brazil in P. motoro, two specimens from Upper Rio Negro, c. Barcelos, Amazonas, Brazil in Potamotrygon sp., one specimen from Upper Rio Negro, c.

Zoologica Scripta, 32, 4, July 2003, pp367– 396 • © The Norwegian Academy of Science and Letters

F. P. L. Marques et al. • Systematics and phylogeny of Potamotrygonocestus

Barcelos, Amazonas, Brazil in P. orbignyi, one detached gravid proglottid from Upper Rio Negro, c. Barcelos, Amazonas, Brazil in P. motoro, four specimens from Lower Rio Solimões, Paraná Janauacá, c. Manaus, Amazonas, Brazil in P. scobina, three specimens from Rio Tocantins, Marabá, Pará, Brazil in P. orbignyi. Potamotrygonocestus magdalenensis Brooks & Thorson, 1976: USNPC 73543 (two paratypes), HWML 37546 (two paratypes), D. R. Brooks personal collection (two specimens). Potamotrygonocestus orinocoensis Brooks, Mayes & Thorson, 1981: USNPC 757714 (two paratypes), HWML 21008, 21009 (five paratypes), HWML 34094 (one voucher), CHIOC 32816a–f (six vouchers). Potamotrygonocestus travassosi Rego, 1979: CHIOC 31487a (holotype), CHIOC 31487b and e (two paratypes), 28 specimens from Lower Amazon, Belém, Pará, Brazil in Paratrygon aiereba, one detached gravid proglottid from Lower Rio Solimões, Lago Janauacá, c. Manaus, Amazonas, Brazil in Potamotrygon constellata, 16 specimens from Lower Rio Solimões, Lago Janauacá, c. Manaus, Amazonas, Brazil in P. motoro. Potamotrygonocestus sp. 1: three specimens from the confluence of Paraná Janauacá and Rio Solimões, c. Manaus, Amazonas, Brazil in Plesiotrygon iwamae. Potamotrygonocestus sp. 2: five specimens from Upper Rio Negro, c. Barcelos, Amazonas, Brazil in Potamotrygon orbignyi, one specimen from Upper Rio Negro, c. Barcelos, Amazonas, Brazil in P. motoro, one detached mature proglottid from Rio Xingu, Altamira, Pará, Brazil in P. leopoldi, two specimens from Paraguay Basin, Puerto Reconquista, Santa Fé, Argentina in P. motoro, one specimen from Upper Paraguay, Corumbá, Mato Grosso, Brazil in P. motoro. Potamotrygonocestus sp. 3: one immature and four incomplete specimens, and three detached proglottides from Praia do Defunto, Rio Negro, c. Barcelos, Amazonas, Brazil in Potamotrygon orbignyi. Potamotrygonocestus sp. 4: three detached proglottides from Rio Tocantins, Marabá, Pará, Brazil in Potamotrygon henlei. Potamotrygonocestus sp. 5: eight detached proglottides from Catalão, confluence of Rio Negro and Rio Solimões, c. Manaus, Amazonas, Brazil in Potamotrygon schroederi. Pedibothrium globicephalum Linton, 1909 USNPC 8995 (three paratypes), USNPC 82045 (five vouchers). Pedibothrium lintoni Caira & Pritchard, 1986 USNPC 79027 (holotype), USNPC 79028 (two paratypes), USNPC 35972 (two vouchers), and USNPC 82041 (six slides). Pedibothrium maccallumi Caira & Pritchard, 1986 USNPC 36011 (holotype). Pedibothrium brevispine Linton, 1909 USNPC 9001 (six paratypes) and USNPC 82046 (five vouchers). Pedibothrium longispine Linton, 1909 USNPC 8992 (holotype), and USNPC 82044 (five vouchers). Pedibothrium kerkmhami (Southwell, 1911) USNPC 82047 (22 vouchers). Phylogenetic analysis The phylogenetic analysis was performed using PAUP* (version 4.1.2a; Swofford 1999) using the exhaustive and


branch-and-bound search algorithm and ACCTRAN optimization. Multistate transformation series were considered unordered, characters were equally weighted, and trees were rooted by specifying Pedibothrium and Pachybothrium as outgroups (see below for the justification of outgroup choice). The characters for Pedibothrium were obtained from specimens deposited in museum collections and for Pachybothrium obtained from Caira & Pritchard (1986). Character distribution was analysed using MACCLADE (version 3.0; Maddison & Maddison 1997). Descriptions Family ONCOBOTHRIIDAE Braun, 1900 Potamotrygonocestus Brooks & Thorson, 1976

Type species. Potamotrygonocestus magdalenensis Brooks & Thorson, 1976. Type host. Potamotrygon magdalenae (Valenciennes, 1865). Generic diagnosis. Scolex with four sessile non-septate bothridia; each with an apical sucker. Hook prongs hollow, each with a channel opening to the outside via a single pore anteriorly adjacent to the base. Cephalic peduncle absent. Scolex and neck bearing microtriches. Strobila acraspedote, hyperapolytic. Genital pores posterolateral, irregularly alternating. Testes numerous, in two preovarian lateral fields; postvaginal testes absent. Vas deferens ascending from the cirrus sac to the level of the anterior third to half of proglottis, recurved posteriorly to the region of posterior-most testes; recurved region glandular. Ovary posterior, bilobed in cross-section. Vagina anterior to cirrus sac. Vitellarian follicles lateral. Uterus medioventral, saccate. Eggs spherical. Parasites of neotropical freshwater potamotrygonids. Potamotrygonocestus magdalenensis Brooks & Thorson, 1976: Fig. 1A–E. Holotype. USNPC 73542. Paratypes. USNPC 73543, HWML 20254. Type host. Potamotrygon magdalenae (Valenciennes, 1865). Site of infection. Anterior portion of the spiral valve. Type locality. Cienaga Rabón, vicinity of San Cristóbal, Bolívar, Colombia. Redescription. Measurements based on specimens from USNPC 73543 (paratype: one immature specimen and one detached proglottis), HWML 37546 (vouchers from type locality: one immature specimen and one detached proglottis), 369


Fig. 1 A–E. Potamotrygonocestus magdalenensis. —A. Scolex (D. R. Brooks’ personal collection). —B. Hooks (D. R. Brooks’ personal collection). — C. Hook of the paratype (USNPC 73543). —D. Mature proglottis (paratype, USNPC 73543). —E. Detail of the cirrus sac (HWML 37546). Scale bars: A, D, E = 100 µm; B, C = 10 µm.

370



and two mature specimens from the personal collection of D. R. Brooks. Strobila acraspedote, hyperapolytic. Immature specimens 1.1–2.2 (1.8 ± 0.5, n = 4) mm long, composed of seven to 17 (11 ± 4, n = 4) proglottides. Scolex 201–330 (248 ± 56, n = 4) long, 222–377 (298 ± 64, n = 4) wide, four bothridia, sessile, non-septate, each with an apical sucker, and a pair of simple hooks at the anterior 10th of the bothridia. Apical sucker 24 – 48 (32 ± 9, n = 8) in diameter. Scolex, neck, strobila bearing microtriches decreasing in density posteriorly (Fig. 1A). Bothridia 194 –318 (263 ± 56, n = 6) long by 116 –161 (135 ± 20, n = 6) wide. Hook prongs emerging from the middle of the handle, hollow with a channel opening to the outside via a single pore anteriorly adjacent to the base (Fig. 1B,C). Lateral hooks 36 –51 (42 ± 7, n = 4) long, prongs 46– 63 (54 ± 7, n = 4) long, bases 17–23 (19 ± 3, n = 4) long. Medial hooks 43–79 (55 ± 15, n = 6) long, prongs 43–79 (55 ± 15, n = 6) long, bases 14 –24 (20 ± 4, n = 6) long. Neck 132–231 (186 ± 50, n = 3) long. Terminal immature proglottides 518 long by 271 wide; detached mature proglottides 1235 long by 302 wide (Fig. 1D). Testes in two longitudinal rows in anterior two thirds of proglottis, 49–98 (78 ± 14, n = 15) long by 35– 83 (56 ± 16, n = 15) wide, 18 –26 (21 ± 3, n = 5) in number; 10–13 (11 ± 1, n = 5) porally, 8 –13 (10 ± 2, n = 5) aporally. Vas deferens ascending from the cirrus sac to the level of the anterior half to third of proglottis, recurved posteriorly to the region of posterior-most testes; recurved region glandular (Fig. 1D). Genital pore at posterior end of proglottis to 4% of proglottis length from posterior end. Genital atrium absent. Cirrus sac 62–98 long by 48–78 wide in mature proglottides, containing spined eversible cirrus (Fig. 1E). Vagina anterior to cirrus sac. Ovary in posterior third of proglottis 82–189 (135 ± 54, n = 3) wide; posterior ovarian lobes may or may not be fused. Aporal arm of ovary 193–361 (269 ± 85, n = 3) long, poral arm 125–306 (216 ± 90, n = 3) long (Fig. 1D). Uterus indistinct in mature proglottides. Vitellarian follicles compact, 11–19 (14 ± 2, n = 10) wide, in two lateral longitudinal rows extending posteriorly to the level of the ovarian isthmus. Gravid proglottides not observed. Remarks. The description of P. magdalenensis by Brooks & Thorson (1976) has been supplemented by Caira & Orringer (1995), who expanded the original description by adding information on the distribution and dimensions of microtriches. In addition, we have also described glandular cells attached to the vas deferens in the portion that descends posteriorly to the region of the most posterior testes (Fig. 1D). Caira & Orringer (1995) illustrated these cells (their fig. 8), but did not comment on them. These glandular cells are found in all species of Potamotrygonocestus (see below) and we consider these cells to be a diagnostic feature of the genus (see generic diagnosis).


Potamotrygonocestus amazonensis Brooks, Mayes & Thorson, 1981: Figs 2A–G, 3A–D. Holotype. USNPC 76363. Paratypes. HWML 21019. Type host. Potamotrygon orbignyi (Castelnau, 1855). Site of infection. Anterior portion of the spiral valve. Type locality. Rio Itacuaí, 5 km south of Atalaia do Norte, Amazonas, Brazil. Other hosts. Potamotrygon falkneri, P. constellata, P. motoro, Potamotrygon sp. (Upper Rio Negro), and P. scobina. Other localities. Upper Paraguay Basin, Corumbá, Mato Grosso, Brazil; Rio Tocantins, Marabá, Belém, Pará, Brazil; Rio Apa, mid-Paraguay, Bela Vista, Mato Grosso do Sul, Brazil; Lower Amazon River, Belém, Pará, Brazil; Upper Rio Negro, near Barcelos, Amazonas, Brazil; and Lower Solimões, c. Manaus, Amazonas, Brazil (Table 2). Redescription. Based on the type series, two mature and five immature specimens. Strobila acraspedote, hyperapolytic; immature specimens 1.4–1.9 (1.6 ± 0.2, n = 4) mm long, composed of 10–13 (11 ± 2, n = 3) proglottides; mature specimens 3.2–3.3 mm long, composed of 12–14 proglottides. Scolex 381–423 (399 ± 17, n = 5) long, 199–372 (321 ± 69, n = 5) wide, comprised of four sessile non-septate bothridia, each with an apical sucker and a pair of simple hooks at the anterior 10th of the bothridia (Fig. 3A–G). Apical sucker 24 –57 (35 ± 15, n = 4) in diameter. Scolex, neck, strobila bearing microtriches decreasing in density posteriorly. Bothridia 356–417 (389 ± 21, n = 6) long by 180–212 (194 ± 12, n = 6) wide (Fig. 3A). Hook prongs emerging from the middle of the handle, hollow with a channel opening to the outside via a single pore anteriorly adjacent to the base (Fig. 3B–G). Lateral hooks 71–77 long, prongs 69–76 long, bases 25–31 long. Medial hooks 75–91 (82 ± 7, n = 6) long, prongs 67–89 (80 ± 9, n = 6) long, bases 22–30 (27 ± 3, n = 5) long. Neck 97–221 (157 ± 51, n = 4) long. Terminal immature proglottides 392–526 (457 ± 68, n = 4) long by 218–281 (256 ± 27, n = 4) wide; mature attached proglottides 651–675 long by 285–293 wide (Fig. 4A). Testes in two longitudinal rows in anterior two thirds of proglottis, 50–91 (67 ± 14, n = 10) long by 38–66 (49 ± 10, n = 10) wide, 20–22 (21 ± 1, n = 3) in number; 10–12 (11 ± 1, n = 3) porally, 10–11 (10 ± 1, n = 3) aporally (Fig. 3A,B). Vas deferens ascending from the cirrus sac to the level of the anterior third of proglottis, recurved posteriorly to the region of posterior-most testes; recurved 371


Fig. 2 A–G. Potamotrygonocestus amazonensis. —A. Scolex (voucher specimen, CHIOC 32816e). —B. Hooks of the holotype (USNPC 76363). —C. Hooks of CHIOC 32816b. —D, E. Hooks of P. amazonensis in Potamotrygon sp. from Upper Rio Negro. —F. Hooks of P. amazonensis in Potamotrygon orbignyi from Rio Tocantins. — G. Hook of voucher specimen (CHIOC 32816e). Scale bars: A = 100 µm; B – G = 10 µm.

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Fig. 3 A–D. Potamotrygonocestus amazonensis. —A. Mature proglottis (paratype, HWML 21019). —B. Mature detached proglottid of

specimen in Potamotrygon orbignyi from Rio Tocantins. — C. Region of ovary of P. amazonensis in Potamotrygon falkneri from Paraguay drainage. — D. Region of cirrus sac (CHIOC 32816a). Scale bars = 100 µm.


373

374

4308.9

P. motoro 4 P. scobina 5

P. orbognyi 6

P. orbognyi 6

(33.6 ± 2.2, n = 3)

— 33.3 –41 (37.5 ± 2.5, n = 10) 31.6 –35.9

P. motoro 4 P. scobina 5

P. orbginyi 4

25.6 –30.8 — 28.9 –35.6 (33.3 ± 2.1, n = 8) 25.9 — 69.3– 86.7 (77 ± 5.8, n = 10) 76.5 –83.6

55.9 –66.8 — 55.5 –62.1 (58.6 ± 2.2, n = 8) 62.8

57.8 –72 (65.1 ± 6.3, n = 5) —

(30.62 ± 2.7, n = 5) —

10

— 28–30

17

24 >18

35.3–35.7

— 37.3

33.2 27.3–30.5 29.8–35.5 (32.4 ± 2.3, n = 8) —

(28.8 ± 1.3, n = 5) 32.7

27.3–30.6

Handle

Lateral hooks

— 302.3–343.8 (320.1 ± 19.5, n = 4) 417.4–435.6 (425.9 ± 9.1, n = 3)

303.7–325.3

345.1 328.2–346.4

324–368.3 (349.3 ± 21.3, n = 4) 341.1 331.1–362.7

Length

— 67.6–83.3 (75.6 ± 4.3, n = 10) 67.6–70.4

63.5–66.2 — 51–63.6 (59.4 ± 3.8, n = 8) 47.4

(64.5 ± 6.4, n = 5) —

53.2–68.5

Length

36–44 (40 ± 3, n = 4) >31 20

Segments

26.2 –33.1

Handle

P. constellata 3 P. motoro 3 Potamotrygon sp.4

P. falkneri 2

P. motoro

1

Prong

— —

P. orbginyi 4

Host /locality

3238.4

P. motoro 3 Potamotrygon sp.4

Medial hooks

3778.4 >1368.8

P. falkneri 2 P. constellata 3

Strobila length

3396–5293.7 (4233 ± 878.2, n = 4) — 4534.9

P. motoro

1

Host /locality

Proglottides

75.8–87.6

— —

66.9 55.4–59.6 52.7–58.2 (56.2 ± 1.8, n = 8) —

(68.4 ± 3, n = 5) 61.7

64.3–72.7

Prong

69.2–69.6

— —

69.8 62.2–65.5 54.7–62.9 (59.4 ± 2.9, n = 8) —

117.8–148.7 (130.8 ± 11.3, n = 5) 109.9 –130.9 139.4 –142.7 (141.4 ± 1.8, n = 3) 139.6 140.7–160.6 (149.8 ± 7.9, n = 7) 149.2–174.2 (163.7 ± 9.6, n = 7) — 105.5 –139.9 (123.2 ± 12, n = 8) 183–245.4 (217.1 ± 28.1, n = 5)

Width

1384.6

1053.4 –1229.1 (1157.4 ± 74.7, n = 4) — — 962.1–1380.2 (1180.6 ± 190.6, n = 5) 1025.8 –1127.2 (1067 ± 53.3, n = 3) — —

—

Length

317.8

261.9–473.1 (346.6 ± 89.7, n = 4) — — 277.9–409.1 (345.1 ± 57.9, n = 5) 364.8–512.6 (420.7 ± 80.2, n = 3) — —

—

Width

Detached mature proglottid

300–341 (324 ± 19, n = 5) 305.7–314.3 276.2–332.5 (298.2 ± 21.6, n = 5) 287.2–288.2 261.6–301.7 (287.2 ± 15.7, n = 7) 279.8–317.4 (298.9 ± 13.9, n = 7) — 240.3–343.8 (290.3 ± 35.2, n = 8) 348.5–396.3 (375.4 ± 20.8, n = 5)

Length

(65.4 ± 3.6, n = 5) 64.8

62.1–69.6

Length

— 241.5–287.7 (256.2 ± 21.3, n = 4) 378.6–463.7 (414.3 ± 44.2, n = 3)

323.4–333.8

249.4 285.2–321.3

285–307.5 (298.1 ± 11.7, n = 3) 223.4 250.4–282.4

Width

Scolex

Table 2 Morphometric parameters (µm) for Potamotrygonocestus amazonensis according to host and geographical area.

35.8

141.9 –265.4 (209.4 ± 51.6, n = 4) — — 183.6 – 256.7 (214.9 ± 32, n = 5) 351.9 –352 (351.9 ± 0.1, n = 3) — —

—

Genital pore position

— 39.3 – 42.3 (41.3 ± 1.7, n = 3) 40 –70.5 (57 ± 13, n = 5)

38.4 – 42.7 44– 58.6 (52.6 ± 4.7, n = 8) 50.5

39.4–47.6 (44.4 ± 2.6, n = 7) 47.2 51.7

Sucker diameter

Bothridia




23 –26 (24 ± 1, n = 4)

Total

9 –12 19–22 (10 ± 1, n = 4) (20 ± 2, n = 4) — 21–27 (25 ± 2.7, n = 4) 6 –9 16–17 (8 ± 2, n = 3) (17 ± 1, n = 3) 9 –12 18–23 (10 ± 1, n = 6) (20 ± 2, n = 6) 11–17 22–31 (14 ± 2, n = 5) (27 ± 4, n = 8) 10 20

—

Antiporal

— — — 8–11 8–12 17–22 (10 ± 1, n = 14) (9 ± 1, n = 14) (19 ± 2, n = 14)

8–10 (9 ± 1, n = 3) 9–11 (10 ± 1, n = 6) 11–15 (13 ± 2, n = 5) 10

10–11 (10 ± 1, n = 4) —

—

Preporal

55.6–129.9 (86.3 ± 20.7, n = 30) 66.1–85.3 (76.5 ± 7.7, n = 5) 49.8–72.2 (62.9 ± 9, n = 5) — 56.3–97.3 (74.9 ± 12.7, n = 25)

51.6–96.5 (73 ± 13.2, n = 20) 46.3–65.5 (56.5 ± 6.2, n = 10) —

65.3–75.2 (71.2 ± 4.2, n = 5)

Length

Testes diameter

2

Upper Paraguay Basin [Corumbá, Mato Grasso, Brazil; collected by Brooks & Amato (1992)]. Mid-Paraguay Basin (Bela Vista, Mato Grosso do Sul, Brazil). 3 Lower Amazon (Belém, Pará, Brazil). 4 Upper Rio Negro (around Barcelos, Amazonas, Brazil). 5 Lower Solimões (Paraná Janauacá, near Manaus, Amazonas, Brazil). 6 Rio Tocantins (Marabá, Pará, Brazil).

1

P. scobina 5 P. orbognyi 6

P. motoro 4

P. orbginyi 4

Potamotrygon sp.4

P. motoro 3

P. constellata 3

P. falkneri 2

P. motoro

1

Host /locality

Testes counts

Table 2 Continued

39.7–115.8 (71.9 ± 20.9, n = 30) 56.7–74.3 (64.6 ± 8.1, n = 5) 33.2–47.7 (41.6 ± 6.4, n = 5) — 41.8–92.2 (66.4 ± 13.4, n = 25)

45.9–67.4 (56.2 ± 5.2, n = 20) 33.8–57.4 (44.8 ± 7.5, n = 10) —

49.3–69.6 (57.8 ± 7.7, n = 5)

Width —

Width 380.1−459.8

Poral lobe

423.5 –520.6

Aporal lobe

Ovary in detached mature proglottides

234.2–263.2

Width

— 72.7

98.6–174.8 (140.1 ± 28.9, n = 5) 104.8–114.6 (111.2 ± 5.5, n = 3) —

—

— 75.8

34.9–73 (50.4 ± 16.1, n = 5) 46.5–57.1 (52.5 ± 5.4, n = 3) —

—

— 266 –304 (287 ± 19, n = 3)

142.9 –366.6 (280.7 ± 83, n = 5) 304.5 –370.7 (342.8 ± 34.3, n = 3) —

—

— 241–282 (264 ± 21, n = 3)

239.7– 442.3 (312.7 ± 84, n = 5) 323.6 – 437 (376.1 ± 57.2, n = 3) —

—

— 157–172 (163 ± 8, n = 3)

113.5 –181.5 (146.4 ± 30.7, n = 5) 173.2–245.9 (198.9 ± 40.8, n = 3) —

—

80.9–142.1 39.9–67.4 173.4 –289.3 236.1–334 94.1–168.9 (112.7 ± 26.6, n = 4) (53.2 ± 12.2, n = 4) (225.8 ± 50.9, n = 4) (280.6 ± 47.4, n = 4) (127.1 ± 31.1, n = 4) — — 409.7 459.9 119.5

—

Length

Cirrus sac in detached mature proglottides


375


Fig. 4 A–E. Potamotrygonocestus travassosi. —A. Scolex (paratype, CHIOC 31487b). —B, C. Apical portion of the scolex of P. travassosi in

Paratrygon aiereba from the Lower Amazon. —D, E. Hooks of P. travassosi in P. aiereba from the Lower Amazon. F, G. Potamotrygonocestus orinocoensis. —F. Scolex of P. orinocoensis (paratype, HWML 21009). —G. Hooks of P. orinocoensis (paratype, HWML 21009). Scale bars: A–C, E = 100 µm; D, E, G = 10 µm. 376



region glandular (Fig. 3A,B). Genital pore 3– 8% of proglottides’ length from posterior end. Genital atrium shallow if present. Cirrus sac 59 – 66 long by 38 –50 wide in mature proglottides, containing spined eversible cirrus (Fig. 3D). Vagina anterior to the cirrus sac. Ovary in posterior third of proglottis 139 –158 wide. Aporal arm of ovary 219–224 long, poral arm 225–256 long in mature proglottides, posterior ovarian lobes may or may not be fused (Fig. 3A–C). Uterus indistinct in mature proglottides. Vitellaria compact, 11–19 (14 ± 2, n = 10) wide, in two lateral longitudinal rows. Gravid proglottides not observed. Additional meristic and morphometric attributes of P. amazonensis from other localities and hosts are given in Table 2. Remarks. Potamotrygonocestus amazonensis resembles P. magdalenensis in having hook prongs emerging from the middle of the handle and a genital pore posterior to the ovarian isthmus. However, P. amazonensis differs from P. magdalenensis in possessing longer bothridia (380–423 vs. 205–330), longer bothridial hooks (lateral hooks 71–77 vs. 26–51 and medial hooks 75–91 vs. 43–78), and in having a shallow genital atrium rather than lacking one. Brooks et al. (1981) suggested that P. amazonensis also differed from P. magdalenensis in having follicular rather than compact vitellaria. Reexamination of the type series for both species, in addition to the specimens collected in this study, revealed that the morphology of the vitellaria is dependent on the development of the proglottis. In general, both species have compact vitellaria. Vitellaria that appear more follicular can usually be observed in proglottides at later stages of development. In the original description of P. magdalenensis, Brooks & Thorson (1976) provided an illustration of a detached proglottis in which the genital pore was found in the extreme posterior margin of the proglottis (their Fig. 4; Fig. 2A of the present study). Re-examination of the type series of P. magdalenensis indicated that the position of the genital pore can vary from the extreme posterior end of the proglottis to up to 4% of the proglottides’ length from its posterior margin. The position of the genital pore in the type series of P. amazonensis ranges from 3 to 8% of the proglottis length from the posterior margin, showing some degree of overlap with P. magdalenensis. However, the extreme distal position of the genital pore observed in most specimens of P. magdalenensis was not observed in specimens of P. amazonensis. Among populations of P. amazonensis sampled in this study (Table 2), the position of the genital pore showed a considerable degree of variability. Genital pore position can range from as low as 3– 8% of proglottis length from the posterior margin, as in the population in Potamotrygon orbignyi (type series) from the Upper Solimões tributaries, to up to 25% in specimens in P. constellata from the Lower Amazon. However, this latter condition, observed in only two specimens of P. amazonensis


from Potamotrygon constellata, is rather unusual, as in most of the specimens collected, the position of the genital pore ranged from 9 to 18% of the proglottis length from the posterior end. This is the only character that showed great variability among the populations sampled. No other morphological, morphometric, or meristic character (see Table 2) seemed to have covariation with other attributes observed in the position of the genital pore. Thus, we consider the pattern observed for the position of the genital pore to be intrapopulational variation. Table 2 shows that specimens of P. amazonensis inhabiting six different host species for six distinct localities had concise morphometric and meristic attributes. Characters historically used in the taxonomy of this group, such as strobilar length, scolex, hooks and proglottid dimensions, did not deviate greatly among populations. The only character that showed a gap among populations was the number of segments and some scolex dimensions. For instance, specimens of P. amazonensis collected in Potamotrygon motoro from the Upper Paraguay Basin, Corumbá, Mato Grosso, Brazil possessed 36–44 segments, whereas the remaining specimens had between 17 and 30 proglottides. However, a single mature worm collected in P. orbignyi from Rio Tocantins had 10 segments. Also, specimens collected in P. orbignyi from Rio Tocantins had larger scolex dimensions than those from other localities and hosts (Table 2). We assume that these discrepancies might be related to either the small sample size or an age factor, as all other characters for this population seemed to overlap with those found in other populations (Table 2). Potamotrygonocestus travassosi Rego, 1979: Figs 4A–G, 5A,B, 6A–C. Synonym. Potamotrygonocestus orinocoensis Brooks, Mayes & Thorson, 1981. Holotype. CHIOC 31487a. Paratypes. CHIOC 31487b and 31487e. Type host. Potamotrygon orbignyi (Castelnau, 1855) (originally recorded as Paratrygon hystrix [sic], but see remarks). Site of infection. Spiral valve. Type locality. Amazon River, Maicuru, Pará, Brazil. Other hosts. Paratrygon aiereba, Potamotrygon constellata, and P. motoro. Other localities. Lower Amazon River, Belém, Pará, Brazil; Paraná Janauacá, c. Manaus, Amazonas, Brazil. 377


Fig. 5 A–C. —A. Undifferentiated juvenile of Potamotrygonocestus travassosi. — B. Detached mature proglottis of P. orinocoensis (paratype,

USNPC 75714). — C. Mature proglottis of P. travassosi in Paratrygon aiereba from the Lower Amazon. Scale bars = 100 µm.

378



Fig. 6 A–C. —A. Detail of the male reproductive system of Potamotrygonocestus travassosi. — B. Ovary region (paratype of P. orinocoensis, USNPC 75714). — C. Ovary region of P. travassosi. Scale bars = 100 µm.


379


Redescription. Measurements based on paratype series: two incomplete specimens. Strobila acraspedote, hyperapolytic. Scolex 319 long by 338 wide, comprising four sessile nonseptate bothridia, each with an apical sucker, and a pair of simple hooks at the anterior quarter of the bothridia. Apical sucker 51–77 (67 ± 11, n = 4) long by 105–116 (111 ± 6, n = 4) wide. Scolex, neck, strobila bearing microtriches decreasing in density posteriorly (Fig. 4A). Bothridia 202– 221 (211 ± 9, n = 4) long by 160–172 (166 ± 5, n = 4) wide. Hooks asymmetrical, prongs hollow with a channel opening to the outside via a single pore anteriorly adjacent to the base, hook prong emerging from the posterior end of the handle. Lateral hooks 127–131 long, prongs 128–130 long, bases 59– 60 long. Medial hooks 117–121 long, prongs 93–98 long, bases 63–65 long. Neck 155 long. Immature proglottides initially wider than long, becoming longer than wide. Mature proglottides not observed. Testes in two longitudinal rows in anterior two thirds of proglottis, 26–27 (26 ± 1, n = 2) in number; 13 (n = 2) porally, 12–14 antiporally. Extended description. Measurements based on new material inhabiting the type host: two complete specimens and one incomplete specimen. Strobila acraspedote, hyperapolytic, immature specimens 1.5–1.7 (1.6 ± 0.2, n = 2) mm long, composed of six to nine (7 ± 2, n = 3) proglottides; mature specimens 2.7 mm long, composed of six proglottides. Scolex 177–265 (223 ± 44, n = 3) long by 226–278 (257 ± 23, n = 4) wide, comprised of four sessile non-septate bothridia, each with an apical sucker, and a pair of simple hooks at the anterior quarter of the bothridia. Apical sucker 35–63 (46 ± 11, n = 7) long by 53–81 (70 ± 11, n = 7) wide. Scolex, neck, strobila bearing microtriches decreasing in density posteriorly. Bothridia 127–229 (160 ± 37, n = 9) long by 92–162 (130 ± 20, n = 10) wide. Hooks asymmetrical, prongs emerging from the posterior end of the handle, hollow with a channel opening to the outside via a single pore anteriorly adjacent to the base. Lateral hooks 80–105 (87 ± 7, n = 12) long, prongs 66–93 (75 ± 7, n = 11) long, bases 30 – 45 (36 ± 4, n = 12) long. Medial hooks 64 – 88 (73 ± 8, n = 7) long, prongs 48–78 (57 ± 13, n = 6) long, bases 31– 43 (37 ± 4, n = 8) long. Neck 142–253 (185 ± 59, n = 3) long. Immature proglottides initially wider than long, becoming longer than wide. Mature attached proglottides 994 long by 240 wide. Testes in two longitudinal rows in anterior two thirds of proglottis, 51–58 (55 ± 3, n = 5) long by 39 – 45 (42 ± 2, n = 5) wide, 24 in number, 10 porally, 14 aporally. Vas deferens ascending from the cirrus sac to the level of the anterior half to third of proglottis, recurved posteriorly to the region of posterior-most testes; glandular region at proximal region of the deferens, immediately after the area where the vas deferens and sperm ducts join (Fig. 6A). Cirrus sac 109 long by 56 wide, in posterior third of proglottis, containing spined eversible 380

cirrus. Genital pore 32% of proglottis length from anterior end, at the level of or slightly anterior to the ovarian isthmus. Genital atrium shallow. Vagina anterior to the cirrus sac. Ovary in posterior third of proglottis, 147 wide. Aporal arm of ovary 327 long, poral arm 345 long in mature attached proglottides; inverted ‘A’ or theta-shaped. Uterus indistinct in mature proglottides. Uterine duct joining uterus near the posterior end. Vitellaria compact, 11–18 (15 ± 3, n = 5) wide, in two lateral longitudinal rows which may or may not overlap the cirrus sac. Gravid proglottides not observed. Additional meristic and morphometric attributes of P. travassosi are given in Table 3. Remarks. This redescription of Potamotrygonocestus travassosi based on the type specimens used by Rego (1979) eliminates the confusion stemming from the inadvertent inclusion of a proglottis of Paroncomegas araya in the original description (Rego 1979: 882, fig. 6), as noted by Brooks et al. (1981). The material used by Rego (1979) included a vial (CHIOC 26499) containing several specimens of P. araya and two slides (CHIOC 31487c, d) containing proglottides of P. araya. However, the holotype (CHIOC 31487a) and two paratypes (CHIOC 31487b, e) allowed us to recognize P. travassosi as a valid species. Examination of the type series of Potamotrygonocestus orinocoensis revealed that this species is a junior synonym of P. travassosi. Brooks et al. (1981) described P. orinocoensis inhabiting Potamotrygon orbignyi from the delta of Rio Orinoco [host identified as P. reticulatus in the original description and later corrected by Brooks & Amato (1992) after Rosa (1985)]. As mentioned above, they pointed out that one of the illustrations provided by Rego (1979: fig. 5) for a bothridial hook suggested that P. orinocoensis and P. travassosi shared some resemblance. Brooks et al. (1981) also suggested that P. orinocoensis closely resembles P. magdalenensis in possessing compact vitellaria, and in lacking a genital atrium. However, full comparisons among these three species could not have been made by the authors, as in their publication they not only acknowledged not having examined specimens of P. travassosi (Brooks et al. 1981: 48), but also because the illustration provided by Rego (1979) for the proglottis belonged to a trypanorhynch. Examination of the type series of P. travassosi and P. orinocoensis revealed few differences between samples, none of which we consider sufficient to recognize two distinct species, as they are not supported by material from subsequent collections. For instance, the handles of the medial and lateral hooks are larger in specimens of the type series of P. travassosi (63– 65 and 59–60, respectively) than those of P. orinocoensis (22–48 and 26–45, respectively). The type series of P. travassosi also possesses longer medial and lateral hook handles compared with the specimens used in this


1.4 –1.7 (1.6 ± 0.1, n = 3) 1.4–2.2 (1.8 ± 0.4, n = 11)

P. travassosi 1V

P. travassosi 3II P. travassosi 3IV


P. fitzgeraldae 7IV

P. fitzgeraldae7IV

P. fitzgeraldae5III P. fitzgeraldae6IV

P. fitzgeraldae 4IV

P. fitzgeraldae 4V

— 85.4 –94.7 (89.4 ± 4.8, n = 3) 87.5

60.8 –71.9 (67.8 ± 4, n = 6) 78.7

32.9 –50.9 (44.9 ± 4.5, n = 31) 39.3–54 (46.8 ± 3.3, n = 18) 35.8 – 42.2 (39.9 ± 3.6, n = 3)

—

— 72.2–99.3 (84.6 ± 6.7, n = 31) 72.3 –98.7 (88.1 ± 7.8, n = 16) 70.5 – 83.6 (77.5 ± 6.6, n = 3)

—

(72 ± 12, n = 15) 47.6 – 88.3 (70.2 ± 7, n = 51)

(40 ± 5, n = 15) 29.9 – 54.2 (44.6 ± 4.4, n = 55)

P. travassosi 2I

P. travassosi 3II P. travassosi 3IV

55 – 91

Handle

30 – 48

Species/locality / host

—

— —

—

—

Segments

—

— —

—

—

—

116.8 –132.4 (127.4 ± 5, n = 7) 139.4

—

83.9 –112.3 (100.8 ± 6.7, n = 31) 82.6–100.7 (94.8 ± 5.1, n = 15) 72.1–86.5 (81.4 ± 8.1, n = 3)

432.2

Handle

(35.1 ± 5.9, n = 13) 30.8 –50.2 (41.2 ± 4.1, n = 53)

56.1–62.1 (59.3 ± 2.2, n = 5) 63.6

—

39–51.7 (44.4 ± 3.4, n = 25) 38.6–53.7 (46 ± 4.4, n = 18) 44– 45.3 (44.8 ± 0.7, n = 3)

141.1–153.8 (147.6 ± 5.6, n = 4) 148.4

—

92.6 –125.1 (107.3 ± 8.9, n = 27) 102.3 –145.7 (130.4 ± 11.8, n = 18) 103 –113.9 (107.1 ± 5.9, n = 3)

—

(93.4 ± 11.1, n = 13) 61.6 –118.6 (93.7 ± 9.7, n = 55)

78.2–109.3

—

— 423.8–434.7

251–289.4 (274.6 ± 13, n = 6) 268.7

—

130.8 –145.2 (137.12 ± 6, n = 5) 141.2

—

92–132.1 (110.2 ± 8, n = 23) 96.1–128.5 (1162.2 ± 9.9, n = 18) 96.3 –101.2 (98.8 ± 2.4, n = 3)

—

(98 ± 17.6, n = 13) 70.7–112.1 (96.1 ± 8.8, n = 48)

Width

186 –241.5 (204.2 ± 19.4, n = 6) 133.7

—

90.2–156.3 (122.3 ± 18.1, n = 42) 100.7–152.4 (130.6 ± 14.7, n = 12) 93.7–97.5 (95.2 ± 2, n = 3)

—

84.5 –127.6 (103.6 ± 16.2, n = 8) 90.1–164.6 (132.7 ± 17.1, n = 55)

83.1–122.6 (104.3 ± 16, n = 7) 90.8

—

—

33–86 (60.1 ± 17.3, n = 32) 52.1–57.1 (54.4 ± 2.5, n = 3)

—

46.6 –77.7 (60.4 ± 10.3, n = 10) 20.4–90.8 (52.1 ± 16.7, n = 22)

Length

Sucker dimension

Width

—

— —

299.4

—

—

325–729.7 (458.1 ± 190.6, n = 4)

231.6–320.8

—

—

(268.5 ± 11.3, n = 3)

259.1–281.1

1876.3

—

1423.9 –1995.2 (1713.6 ± 286.9, n = 4)

726.8 –1609.7

—

—

(937.6 ± 24, n = 3)

912.9 –960.8

Length

Detached mature proglottides

141.9 –215.6 (182.6 ± 19.5, n = 45) 144.6–176.3 (162.9 ± 10, n = 12) 120.8 –139.4 (129.5 ± 9.4, n = 3)

—

147.5 –190.6 (173.3 ± 15.2, n = 9) 143.3 –242.2 (181.8 ± 24.5, n = 55)

Length

Bothridia

71.3–125

Length

214.1– 322.6 (264.2 ± 37.6, n = 16) 265 –305.3 (291.4 ± 15.5, n = 5) 243.9

—

430.4 – 474.3

26.3 – 45.2

—

Width 181.1–267.9 (211 ± 33.7, n = 5) 233.9 –338.3 (278.5 ± 28, n = 28)

—

Prong

240.5 –312.4 (276.4 ± 22.4, n = 16) 222.1– 248 (233.2 ± 9.7, n = 5) 187.7

—

223.8 –316.1 (273.9 ± 34.5, n = 5) 197.8 –333.4 (249 ± 31.4, n = 27)

Length

Scolex

Lateral hook

8 –13 (10 ± 2, n = 3)

—

6–10 (7 ± 1, n = 10)

—

(86 ± 10, n = 15) 60 –105 (89 ± 7, n = 53)

67–104

Length

1.7–1.8 (1.8 ± 0.06, n = 3)

—

2.3–3.6 (3.1 ± 0.5, n = 10)

—

Size (mm)

Mature specimens

P. travassosi 1V

7

Prong

4.1

P. fitzgeraldae 5III P. fitzgeraldae 6IV

Medial hook

— —

P. fitzgeraldae 4IV

— —

9 –14 (11 ± 1, n = 12) 24–37 (31 ± 5, n = 7) 15

P. fitzgeraldae 4V

—

1–2.3 (1.7 ± 0.4, n = 12) 3–6 (4.5 ± 1.1, n = 7) 2.6

7– 8 (7 ± 1, n = 3) 4– 8 (6 ± 2, n = 14)

Segments

—

P. travassosi 2I

Size (mm)

Species/ locality/host

Immature specimens

Table 3 Morphometric parameters for two species of Potamotrygonocestus according to host and geographical area.

Width

—

—

471.1

—

262.7–621.3 (463.3 ± 179.1, n = 4)

194.7–383

—

—

(290.1 ± 24.2, n = 3)

266.6–315

Genital pore

117–139 (125.5 ± 9.2,n = 7) 97.8

—

22.8 –152.2 (61.7 ± 19.2, n = 40) 38.4–77.7 (61.9 ± 12.4, n = 9) 41.6 –53.7 (46.9 ± 6.2, n = 3)

—

46.9 – 62.5 (56.3 ± 6, n = 8) 53.5 –106.9 (83.7 ± 11.6, n = 43)


381

382

10 –11 (11 ± 1, n = 3) 10 –14 (12 ± 1, n = 27) 12

9 –12 (10 ± 1, n = 29) 12–23 (10 ± 4, n = 10) 18

18

17–23 (20 ± 3, n = 4) —

P. travassosi 3IV

P. fitzgeraldae 4IV

P. fitzgeraldae 5III

P. fitzgeraldae 6IV

5

1

2

Antiporal

17–24 (21 ± 3, n = 4) —

18

9 –15 (11 ± 2, n = 29) 11–22 (15 ± 3, n = 10) 19

10 –12 (11 ± 1, n = 3) 10 –16 (12 ± 2, n = 27) 11

Total

34– 46 (41 ± 6, n = 4) —

32

3

18–27 (21 ± 2, n = 29) 23– 44 (31 ± 7, n = 10) 37

20 –23 (22 ± 2, n = 3) 20–30 (24 ± 3, n = 27) 23

57.4– 66.4 (61.4 ± 4, n = 5) 47.5– 83.1 (62.9 ± 7.3, n = 70) 110.2–140.8 (122.2 ± 13.3, n = 5) 44.8 –103 (65.7 ± 13.8, n = 45) 50.2–103.7 (756 ± 14.7, n = 20) 40.9–48 (45.1 ± 2.6, n = 5) 50.8–67.9 (57 ± 6.5, n = 5) 52.7– 65.8 (61 ± 4.2, n = 10) —

Length

Testes diameter Width

4

48.5 –56.6 (52.9 ± 4, n = 5) 9.4– 67.7 (49 ± 8.2, n = 70) 83.5–93.9 (87.8 ± 4.3, n = 5) 34.1– 96.4 (55.2 ± 14.2, n = 45) 31.3 – 80.2 (56.7 ± 11.4, n = 20) 31–34 (32.6 ± 1.1, n = 5) 35.8 – 46.8 (42.1 ± 4.5, n = 5) 35–52.8 (43.8 ± 6.4, n = 10) — —

155.3

120.1

68.2–192.5 (136 ± 56.7, n = 5) —

89.5 –109.9

103.6 –124.1 (111.7 ± 10.9, n = 3) 122.2–254.7 (190.6 ± 52.5, n = 7) —

Length

—

56.1

38.9

34.4–102.3 (62.7 ± 26.4, n = 5) —

21.6– 41

39.2– 44.8 (42.1 ± 2.8, n = 3) 33 –505.5 (300.9 ± 185.9, n = 7) —

Width

Cirrus sac in detached mature proglottid

—

—

315.6

242.4–411.8 (341.2 ± 88.1, n = 3 —

166.1–381.4

—

2712.2–308.5 (284.3 ± 20.9, n = 3) —

Poral lobe

—

—

405.3

218.6–518.2 (411 ± 167, n = 3) —

173 – 400.1

—

272.3–322.7 (294.1 ± 25.9, n = 3) —

Aporal lobe

Ovary in detached mature proglottid Width

—

—

102.3

128.5 –187.5 (152 ± 31.3, n = 3) —

105.4–148.1

—

124.2–129.6 (127 ± 2.7, n = 3) —

Orinoco (type series of P. orinocoensis). Lower Amazon (Belém, Pará, Brazil). Lower Rio Solimões (Manaus, Amazonas, Brazil). Upper Rio Negro (around Barcelos, Amazonas, Brazil). Rio Xingu (Altamira, Pará, Brazil). 6Lower Paraná (Puerto Reconquista, Santa Fé, Argentina). 7Upper Paraguay (Corumbá, Mato Grosso, Brazil). Hosts: IParatrygon aiereba; IIPotamotrygon constellata; IIIP. leopoldi; IVP. motoro; VP. orbignyi.

P. fitzgeraldae 7IV

P. fitzgeraldae 4V

P. travassosi 3II

P. travassosi 2I

Preporal

P. travassosi 1V

Testes counts

Species/locality / host

Table 3 Continued




redescription which were collected from the type host in the same geographical area (see above) of the type series, and compared with specimens collected from other hosts from different localities (Table 3). The type material used in the present description is restricted to two incomplete specimens (as part of the paratypes were proglottides of Paroncomegas) which suggest caution when differentiating the two species based on those characteristics. Another difference between the type series of P. travassosi and P. orinocoensis is in the morphology of the scolex. Rego (1979: 883) noticed that in P. travassosi the ‘accessory sucker was not observed, although it does probably exist’ (translation by FPLM). In the specimens of the type series of P. orinocoensis, the apical sucker is well defined (cf. Fig. 4A,F). In fact, reexamination of the paratype of P. travassosi (CHIOC 31487b) revealed that the apical sucker is not discernible (Fig. 4A). After examining a considerable number of specimens, which we attributed to P. travassosi, we concluded that the lack of apical sucker, observed in the type series of P. travassosi, might be an artefact of fixation. We were unable to collect anything that resembled the paratype of P. travassosi, even in the type host in regions close to the type locality. However, some intermediate stages between the condition observed in P. travassosi and that of the type series of P. orinocoensis were observed in a few specimens from various localities (Fig. 4B,C). Hence, we consider this character insufficient to justify the recognition of two species. In fact, morphometric and meristic attributes for P. travassosi collected in four different host species from three different localities overlap greatly (Table 3) suggesting some degree of variation among populations, although they seemed to be continuous. Potamotrygonocestus travassosi resembles P. amazonensis and P. magdalenensis in having compact vitellaria and similar numbers of testes (18 –30, 16 –31, and 18 –26, respectively). However, P. travassosi differs from these two species in having asymmetrical hooks at the anterior quarter of the bothridia rather than symmetrical ones at the anterior 10th of the bothridia, hook prongs emerging from the posterior end of the handle rather than at the middle, and in having the genital pore at the level of, or anterior to, the ovarian isthmus rather than posterior to it. Brooks et al. (1981) described P. orinocoensis as possessing a unique theta-shaped ovary (Figs 5B, 6B). This character showed some degree of variability. In attached mature proglottides, the ovary tends to have an inverted ‘A’ shape, in which the anterior poral ovarian lobe may be medially displaced by the cirrus sac (Fig. 5C). The theta-shaped ovary (Fig. 6B) is generally found in detached mature or gravid proglottides, but such proglottides may occasionally possess an inverted ‘A’-shaped ovary. Potamotrygonocestus chaoi n. sp.: Fig. 7A–D.


Holotype. MZUSP 5837. Paratypes. MZUSP 5838–5844. Type host. Plesiotrygon iwamae Rosa, Castello & Thorson, 1987. Site of infection. Anterior portion of the spiral valve. Type locality. Confluence of Paraná Janauacá and Rio Solimões, c. Manaus, Amazonas, Brazil. Etymology. This species is named after Labbish Chao, Universidade do Amazonas, Manaus, Amazonas, Brazil. Description. Based on three incomplete specimens and 26 detached proglottides. Strobila acraspedote, hyperapolytic, composed of more than 44 to more than 55 proglottides. The specimens collected were broken, suggesting that complete specimens have more proglottides than reported herein. Scolex 494–534 (509 ± 22, n = 3) long by 568–627 (600 ± 30, n = 3) wide, comprised of four sessile non-septate bothridia, each with an apical sucker, and a pair of simple hooks at the anterior third of the proglottides (Fig. 7A). Apical sucker 115–150 (136 ± 13, n = 6) long by 159–212 (183 ± 13, n = 11) wide. Scolex, neck, strobila bearing microtriches decreasing in density posteriorly. Bothridia 278–329 (299 ± 13, n = 10) long by 216 –309 (267 ± 25, n = 10) wide. Hooks asymmetrical, prongs emerging from the posterior end of the handle, with a channel opening to the outside via a single pore anteriorly adjacent to the base (Fig. 7C). Lateral hooks 126–154 (145 ± 9, n = 10) long, prongs 120–138 (132 ± 6, n = 10) long, bases 63–78 (72 ± 5, n = 10) long. Medial hooks 134–152 (143 ± 5, n = 11) long, prongs 89–107 (101 ± 5, n = 11) long, bases 77–87 (83 ± 2, n = 11) long. Neck 950 long. Immature proglottides initially wider than long, becoming longer than wide. Detached mature proglottides 1869–2504 (2112 ± 244, n = 8) long by 432–603 (506 ± 57, n = 8) wide; detached gravid proglottides 2110–5432 (3492 ± 1043, n = 10) long by 411–1323 (645 ± 264, n = 10) wide (Fig. 7B) and detached postgravid proglottides 4317–4723 long by 499–536 wide. Testes in two longitudinal rows in anterior two thirds of proglottis, 54–144 (87 ± 21, n = 80) long by 47–114 (69 ± 15, n = 80) wide, 64–107 (87 ± 17, n = 20) in number; 33–63 (45 ± 8, n = 20) porally, 29–53 (41 ± 6, n = 20) aporally (Fig. 7B). Vas deferens ascending from the cirrus sac to the level of the anterior third of proglottis, recurved posteriorly to the region of posterior-most testes; recurved region glandular. Cirrus sac in posterior quarter of proglottis containing spined eversible cirrus, 137–194 (162 ± 22, n = 8) long by 50–64 (60 ± 5, n = 8) wide in detached mature proglottides; 124–245 (178 ± 37, n = 10) long by 59–93 (78 ± 11, n = 10) 383


Fig. 7 A–D. Potamotrygonocestus chaoi n. sp. —A. Scolex. —B. Gravid detached proglottis. —C. Bothridial hooks. —D. Cirrus sac region. Scale bars: A, B, D = 100 µm; C = 50 µm.

384



wide in detached gravid proglottides (Fig. 7D); and 193–218 long by 107–108 wide in detached postgravid proglottides. Genital pore 18 –28% of proglottis length from posterior end. Genital atrium absent. Vagina anterior to the cirrus sac. Ovary inverted ‘A’ shape, posterior ovarian lobes not fused; in posterior third of proglottis, 209 –328 (267 ± 44, n = 8) wide at the isthmus region. Aporal arm of ovary 387–588 (491 ± 75, n = 8) long, poral arm 298–541 (439 ± 83, n = 8) long in detached mature proglottides; and 246–579 (362 ± 94, n = 10) wide, aporal arm 575–1361 (858 ± 241, n = 10) long, poral arm 424 –1212 (739 ± 244, n = 10) long in detached gravid proglottides. Uterus indistinct in mature proglottides. Vitellaria compact 14 –56 (27 ± 8, n = 118) wide, in two lateral longitudinal rows overlapping the cirrus sac (Fig. 7D). Remarks. Potamotrygonocestus chaoi is only known from Plesiotrygon iwamae. Indeed, it is the only cestode that has been reported from this species of freshwater potamotrygonid. The new species most closely resembles P. travassosi in possessing asymmetrical hooks at the anterior third to quarter of the proglottides and hook prongs emerging from the posterior end of the handle. However, P. chaoi differs from P. travassosi in possessing a longer scolex (494 –534 vs. 199 – 474) and a greater number of testes (64 –107 vs. 20–30). Potamotrygonocestus chaoi differs from P. amazonensis and P. magdalenensis in the symmetry of bothridial hooks (asymmetrical vs. symmetrical), the position of the bothridial hooks (at the anterior third rather than at the anterior 10th of the bothridia), insertion of the hook prongs (at the posterior end of the handle rather than at the middle), and the position of the genital pore (anterior to ovarian isthmus rather than posterior). Potamotrygonocestus fitzgeraldae n. sp.: Figs 8A–C, 9A–D. Holotype. MZUSP 5845. Paratypes. MZUSP 5846 – 5853. Type host. Paratrygon aiereba (Müller & Henle, 1841). Type locality. Upper Rio Negro, near Barcelos, Amazonas, Brazil. Other hosts. Potamotrygon leopoldi, P. motoro, and P. orbignyi. Other localities. Rio Xingu, Altamira, Pará, Brazil; Lower Paraguay, Puerto Reconquista, Santa Fé, Argentina; Upper Paraguay, Corumbá, Mato Grosso, Brazil. Site of infection. Anterior portion of the spiral valve. Etymology. This species is named in honour of one of the greatest jazz singers, Ms Ella Fitzgerald.


Description. Based on 11 mature and 18 immature complete specimens, 10 incomplete specimens, and 47 detached proglottides. Strobila acraspedote, hyperapolytic, immature proglottides 1–4 (2.4 ± 0.8, n = 15) mm long, composed of five to 23 (16 ± 5, n = 15) proglottides; mature specimens 1.6–4.1 (2.6 ± 0.7, n = 11) mm long, composed of 10–19 (15 ± 3, n = 10) proglottides. Scolex 108–271 (221 ± 29, n = 31) long, 126–325 (250 ± 34, n = 30) wide, comprised of four sessile non-septate bothridia, each with an apical sucker, and a pair of simple hooks at the anterior quarter of the bothridia. Apical sucker 24–77 (43 ± 9, n = 57) long by 38–77 (55 ± 8, n = 83) wide. Scolex, neck, strobila bearing microtriches decreasing in density posteriorly (Fig. 8A). Bothridia 112–188 (153 ± 17, n = 82) long by 74–148 (112 ± 13, n = 93) wide. Hooks asymmetrical, prongs emerging from the posterior end of the handle, hollow with a channel opening to the outside via a single pore anteriorly adjacent to the base (Fig. 8C). Lateral hooks 80–137 (100 ± 10, n = 74) long, prongs 85–128 (108 ± 10, n = 71) long, bases 33–52 (43 ± 4, n = 75) long. Medial hooks 52–104 (80 ± 9, n = 97) long, prongs 60–95 (75 ± 8, n = 98) long, bases 31–49 (40 ± 4, n = 99) long. Neck 84–236 (155 ± 35, n = 19) long. Terminal immature proglottides 389–852 (647 ± 122, n = 15) long by 165–334 (220 ± 47, n = 15) wide; mature attached proglottides 691–872 (768 ± 60, n = 6) long by 152–310 (234 ± 59, n = 6) wide (Fig. 9A); detached mature proglottides 1105–2988 (1796 ± 517, n = 30) long by 222–581 (357 ± 81, n = 30) wide (Fig. 8B); detached gravid proglottides 1317–2681 (2070 ± 480, n = 8) long by 306–719 (508 ± 129, n = 8) wide, and detached postgravid proglottides 2970 long by 656 wide. Testes in two longitudinal rows in anterior two thirds of proglottis (Figs 8B, 9A), 24–103 (67 ± 17, n = 193) long by 17–84 (50 ± 13, n = 193) wide, 20–48 (34 ± 6, n = 69) in number; 10–24 (17 ± 3, n = 68) porally, 10–24 (17 ± 3, n = 68) aporally. Vas deferens ascending from the cirrus sac to the level of the anterior third of proglottis, recurved posteriorly to the region of posterior-most testes; recurved region glandular. Cirrus sac in posterior third to quarter of proglottis, containing spined eversible cirrus (Fig. 9B); 80–115 (98 ± 15, n = 6) long by 19–43 (33 ± 9, n = 6) wide in mature attached proglottides; 89–199 (131 ± 31, n = 28) long by 32–68 (48 ± 8, n = 28) wide; 114–152 (133 ± 15, n = 7) long by 53–65 (59 ± 5, n = 7) wide in detached gravid proglottides; and 135 long by 66 wide in detached postgravid proglottides. Genital pore 22–27% of proglottis length from posterior end. Genital atrium shallow. Vagina anterior to the cirrus sac. Ovary inverted ‘A’ shape or theta-shaped (Figs 8A, 9A,C), at posterior third of proglottis 76–213 (129 ± 56, n = 5) wide at the isthmus region, aporal arm 166–204 (193 ± 15, n = 5) long, poral arm 152–195 (175 ± 16, n = 5) long in mature attached proglottides; 74–220 (142 ± 41, n = 28) wide, aporal arm 147–730 (379 ± 143, n = 29) long, poral arm 134–621 385


Fig. 8 A–C. Potamotrygonocestus fitzgeraldae n. sp. —A. Scolex. —B. Detached mature proglottis. —C. Bothridial hooks. Scale bars:

A, B = 100 µm; C = 10 µm.

386



Fig. 9 A–D. Potamotrygonocestus fitzgeraldae n. sp. —A. Mature proglottis. —B–D. Ovary region. Scale bars = 100 µm.


387


(318 ± 126, n = 29) long in mature detached proglottides; 141–267 (206 ± 38, n = 8) wide, aporal arm 259–565 (448 ± 100, n = 8) long, poral arm 247–516 (399 ± 89, n = 8) long in detached gravid proglottides, ovarian lobes may or may not be fused (Fig. 9A–C). Uterus indistinct in mature proglottides. Vitellaria compact 5– 44 (19 ± 9, n = 179) wide in two lateral longitudinal rows overlapping the cirrus sac. Additional meristic and morphometric attributes of P. fitzgeraldae are given in Table 3.

Type host. Potamotrygon orbignyi (Castelnau, 1855).

Remarks. Potamotrygonocestus fitzgeraldae resembles P. travassosi and P. chaoi in having asymmetrical hooks with prongs emerging from the posterior end of the bases, hooks approximately one third of the total bothridial length from the anterior end, and a cirrus sac at the level of, or anterior to, the ovarian isthmus. In possessing these characteristics, P. fitzgeraldae differs from P. amazonensis and P. magdalenensis in which the hooks are symmetrical with prongs emerging from the middle of the handle, the hooks are at the anterior 10th of the bothridia, and the cirrus sac is posterior to the ovarian isthmus. Potamotrygonocestus fitzgeraldae most closely resembles P. travassosi in the dimensions of the hooks, testes diameter, and ovary dimensions (see Table 3). However, P. fitzgeraldae differs from P. travassosi in possessing more testes (an average of 31– 41 vs. 21–24, Table 3), and in having a genital pore at the level of the anterior end of the poral ovarian lobe (Fig. 8B) rather than at, or slightly anterior to, the ovarian isthmus (Fig. 5B,C). Potamotrygonocestus fitzgeraldae further differs from P. chaoi in having a shorter scolex (189– 474 vs. 494 –534) and fewer testes (23– 46 vs. 64 –107). The population of P. fitzgeraldae from the Paraná Basin inhabiting Potamotrygon motoro differs morphometrically and meristically from other populations in the Amazon Basin (Table 3). For instance, specimens from the Paraná Basin possess longer scolexes (430 – 474 vs. 188–312), longer hook handles (61–72 vs. 33–51 for medial hooks, and 56 –64 vs. 39–54 for lateral hooks), and more testes (an average of 41 vs. an average of 31–37 testes). However, few representatives of this population could be examined. We examined only two complete specimens and few proglottides from the Lower Paraná system in addition to one specimen collected by Brooks & Amato (1992) from the mid-Paraguay drainages [HWML 34094, identified by Brooks & Amato (1992) as P. orinocoensis]. Whether the population from the Paraná– Paraguay drainages constitutes a distinct species is pending the collection of additional material. Potamotrygonocestus maurae n. sp.: Fig. 10A–D.

Etymology. The species is named after Maura Kumagay for her kind hospitality during our field work in Belém do Pará, Brazil.

Site of infection. Anterior portion of the spiral valve. Type locality. Praia do Defunto, Rio Negro, near Barcelos, Amazonas, Brazil. Other localities. Rio Branco, 4 h from confluence with Rio Negro (host deposited UFPB 3536).

Description. Based on one immature and four incomplete specimens, and three detached proglottides. Strobila acraspedote, hyperapolytic, immature specimens 3.2 mm long, composed of 17 proglottides. Scolex 303–325 long by 323–334 wide, comprised of four sessile non-septate bothridia, each with an apical sucker, and a pair of simple hooks at the anterior 10th of the bothridia. Apical sucker 55 in diameter. Scolex, neck, strobila bearing microtriches decreasing in density posteriorly (Fig. 10A). Bothridia 280–317 (299 ± 14, n = 7) long, 149–174 (164 ± 10, n = 7) wide. Hooks 47 long, prongs 63 long, bases 26 long. Hook prongs emerging from the middle of the handle, hollow with a channel opening to the outside via a single pore anteriorly adjacent to the base (Fig. 10B). Immature proglottides initially wider than long, becoming longer than wide. Detached mature proglottides 1026–1127 (1067 ± 53, n = 3) long, 365–513 (421 ± 80, n = 3) wide (Fig. 10C). Testes in anterior two thirds of proglottis, 66 – 85 (76 ± 8, n = 5) long by 57–74 (65 ± 8, n = 5) wide, 22–31 (27 ± 4, n = 8) in number; 11–15 (13 ± 2, n = 5) porally, and 11–17 (14 ± 2, n = 5) aporally. Vas deferens ascending from the cirrus sac to approximately the level of the anterior third of proglottis, recurved posteriorly to the region of posterior-most testes; recurved region glandular (Fig. 10C). Cirrus sac in posterior third of proglottis, 105–115 (111 ± 5, n = 3) long by 46–57 (52 ± 5, n = 3) wide in detached mature proglottides, containing spined eversible cirrus (Fig. 10D). Genital pore 31–34% of proglottis length from posterior end. Genital atrium shallow. Vagina anterior to the cirrus sac. Ovary in posterior third of proglottis 173–246 (± , n =) wide. Aporal arm of ovary 324–437 (376 ± 57, n = 3) long, poral arm 304–371 (343 ± 34, n = 3) long in detached mature proglottides. Uterus indistinct in mature proglottides. Vitellaria compact 26–38 (30 ± 5, n = 5) wide, in two lateral longitudinal rows extending to the posterior level of the ovary. Gravid proglottides not observed.

Holotype. MZUSP 5854. Paratypes. MZUSP 5855–5857. 388

Remarks. Potamotrygonocestus maurae resembles P. amazonensis and P. magdalenensis in having symmetrical bothridial hooks



Fig. 10 A–D. Potamotrygonocestus maurae n. sp. —A. Scolex. —B. Bothridial hooks. —C. Mature detached proglottis. —D. Cirrus sac region. Scale bars: A, C, D = 100 µm; B = 10 µm.


389


at the anterior 10th of the bothridia, hook prongs emerging from the middle of the prong and having approximately 20 testes. Conversely, the new species differs from P. travassosi, P. chaoi, and P. fitzgeraldae in which the bothridial hooks are asymmetrical, at the anterior third to quarter of the bothridia and prongs emerge from the posterior end of the handle. Potamotrygonocestus maurae further differs from P. amazonensis and P. magdalenensis in having a genital pore at the level of the anterior end of the poral ovarian lobes rather than at the level of, or posterior to, the ovarian isthmus. The diagnostic character for this species is the extension of vitellaria to the posterior end of ovarian lobes. In other species of Potamotrygonocestus, the vitellaria reach the level of the ovarian isthmus at the most. Potamotrygonocestus sp. 7: Fig. 11A. Host. Potamotrygon henlei (Castelnau, 1855). Locality. Rio Tocantins, Marabá, Pará, Brazil. Vouchers. MZUSP 5858.

postgravid proglottides 1876–3580 (2875 ± 537, n = 7) long by 657–843 (738 ± 59, n = 7) wide (Fig. 11B). Testes in two longitudinal rows in the anterior two thirds of proglottis, 76–172 (127 ± 23, n = 40) long by 77–151 (110 ± 18, n = 40) wide, 23–32 (28 ± 3, n = 8) in number. Vas deferens ascending from the cirrus sac to the level of the anterior two thirds of proglottis, recurving posteriorly to the region of posteriormost testes; recurved region glandular. Cirrus sac in posterior 10th of proglottis, 192 long by 102 wide in detached mature proglottides, containing spined eversible cirrus (Fig. 11B,C). Genital pore 9–11% of proglottis length from posterior end. Genital atrium not observed. Vagina anterior to the cirrus sac. Ovary in posterior third of proglottis 220 wide, aporal arm 531 long, poral arm 326 long in detached mature proglottides; and 252–367 (321 ± 44, n = 5) wide. Aporal arm of ovary 601–976 (641 ± 28, n = 5) long, poral arm 309–517 (417 ± 94, n = 5) long; poral arm displaced towards the midline by the cirrus sac. Uterus indistinct in mature proglottides. Vitellaria compact in two lateral longitudinal rows 27–80 (51 ± 12, n = 55) wide not reaching the cirrus sac region.

Type locality. Catalão, confluence of Rio Negro and Rio Solimões, near Manaus, Amazonas, Brazil.

Remarks. These specimens may represent two undescribed species of Potamotrygonocestus. In order to be recognized as distinct species, further collections of additional specimens must be made. Proglottides of Potamotrygonocestus sp. 7 resemble those of P. travassosi, P. chaoi, and P. fitzgeraldae with an inverted ‘A’ ovarian shape and a genital pore at the level of, or anterior to, the ovarian isthmus. However, the number of testes (46–55) is greater than expected for P. travassosi (20–30) and in between the numbers recorded for P. fitzgeraldae (23–46) and P. chaoi (64 –107). Because only three detached proglottides of Potamotrygonocestus in Potamotrygon henlei from Rio Tocantins were collected, it is difficult to ascertain the taxonomic status of these specimens without further data. The proglottides assigned to Potamotrygonocestus sp. 8 resemble those of P. amazonensis, P. magdalenensis and P. maurae in having a relatively low number of testes (20) and a genital pore at the level of, or posterior to, the ovarian isthmus. However, Potamotrygonocestus sp. 8 differs from these species in having asymmetrical ovarian lobes (Fig. 11B). In addition, Potamotrygonocestus sp. 8 differs from P. magdalenensis by having the genital pore at the level of the ovarian isthmus rather than at the posterior end of the proglottis. It also differs from P. maurae by having vitellaria extending only to the level of the ovarian isthmus rather than to the level of the posterior end of the ovarian lobes.

Vouchers. MZUSP 5859–5864.

Key for species of Potamotrygonocestus

Description. Based on eight detached proglottides. Detached mature proglottides 2369 long by 713 wide, and detached

1a Bothridial hooks asymmetrical at the anterior third to quarter, hook prongs emerging from the posterior end of the handle: 4.

Description. Based on three detached proglottides. Detached gravid proglottides 4558 long by 802 wide; detached postgravid proglottides 4968 long by 611 wide (Fig. 11A). Testes in two longitudinal rows in anterior two thirds of proglottis, 132–161 (148 ± 13, n = 5) long by 97–146 (125 ± 21, n = 5) wide, 46 –55 (51 ± 5, n = 3) in number; 26 –27 (26 ± 1, n = 3) porally, and 20 –28 (25 ± 4, n = 3) aporally. Vas deferens ascending from the cirrus sac to the level of the anterior half of proglottis, recurved posteriorly to the region of posteriormost testes; recurved region glandular. Cirrus sac in posterior quarter of proglottis containing spined eversible cirrus, 219 long by 109 wide in detached gravid proglottides, 270 long by 113 wide in detached postgravid proglottides. Genital pore 22–29% of proglottis length from posterior end. Genital atrium shallow. Vagina anterior to the cirrus sac. Ovary in posterior quarter of proglottis 452– 483 wide, aporal arm 941–1257 long, poral arm 817–1066 long in detached gravid proglottides. Uterus indistinct in mature proglottides. Vitellaria compact 42– 64 (54 ± 9, n = 6) wide, in two lateral longitudinal rows overlapping the cirrus sac. Potamotrygonocestus sp. 8: Fig. 11B,C. Type host. Potamotrygon schroederi Fernándedez-Yépez, 1957.

390



Fig. 11 A–C. —A. Potamotrygonocestus sp. 7 detached gravid proglottis. —B, C. Potamotrygonocestus sp. 8 detached mature proglottis and cirrus

sac region, respectively. Scales bars: A = 1 mm; B, C = 100 µm.


391


1b Bothridial hooks symmetrical at the anterior 10th, hook prongs emerging from the middle of the handle: 2. 2a Genital pore at the level of, or posterior to, the level of the ovarian isthmus; vitellaria not extending posteriorly to the ovarian isthmus: 3. 2b Genital pore at the level of the anterior end of the poral ovarian lobe; vitellaria extending to the level of the posterior end of the ovarian lobes: P. maurae. 3a Bothridia 380– 423 µm long, lateral bothridial hooks 71–77 µm long, medial hooks 75–91 µm long, shallow genital atrium present: P. amazonensis. 3b Bothridia 205–330 µm long, lateral bothridial hooks 26 –51 µm long, medial hooks 43–78 µm long, genital atrium absent: P. magdalenensis. 4a Fewer than 50 testes per proglottides: 5. 4b More than 50 testes per proglottides: P. chaoi. 5a Genital pore at the level of, or slightly above, the ovarian isthmus, 21–24 testes on average: P. travassosi. 5b Genital pore at the level of the anterior end of the poral ovarian lobe, 31– 41 testes on average: P. fitzgeraldae.

Outgroup comparison and phylogenetic analysis Outgroup choice Species of Potamotrygonocestus have scoleces with a relatively simple structure compared with other onchobothriid tetraphyllideans. They possess simple hooks and non-septate bothridia. Of the genera currently recognized as comprising the Onchobothriidae Braun, 1900, only Spiniloculus Southwell, 1925, Yorkeria Southwell, 1930, and Pachybothrium Baer & Euzet, 1962 share these characteristics. Balanobothrium Hornel, 1911 and Pedibothrium Linton, 1909 also exhibit non-septate bothridia but have bifid hooks. Spiniloculus and Yorkeria appear to be closely related and divergent from the rest of the onchobothriids by having forked scoleces and hooks without bases or internal channels. Balanobothrium, Pachybothrium, Pedibothrium, and Potamotrygonocestus all have hook prongs possessing separate channels with separate pores (Fig. 12A,B). Caira & Pritchard (1986) suggested that this character could not be considered a synapomorphy for Pedibothrium because of its presence in Pachybothrium. However, we consider this character to be a putative synapomorphy for Balanobothrium, Pachybothrium, Pedibothrium, and Potamotrygonocestus. Pachybothrium, Pedibothrium, and Potamotrygonocestus lack postvaginal testes on the poral side, which we consider to be a synapomorphy for these three genera. Thus, Pachybothrium and Pedibothrium served as outgroups for the phylogenetic analysis of Potamotrygonocestus based on the putative synapomorphies listed above, supporting the original outgroup choice of Brooks et al. (1981). The monophyly of Potamotrygonocestus was based on the following putative synapomorphies: the presence of simple hooks in which the length of the hook prongs are about twice the 392

Fig. 12 A, B. —A. Typical hook morphology of Pedibothrium. —B.

Typical hook morphology of Pachybothrium. Scales omitted.

length of the base rather than simple or bifid hooks with same size prongs as the base, the presence of glandular cells surrounding the vas deferens, genital pore posterior to the anterior margins of the ovarian arms rather than distinctly preovarian, and testes restricted to the preovarian space. Character argumentation The characters used in the analysis are summarized in the data matrix shown in Table 4 with the following polarization decisions: 1 Attachment of the base of the hook prong. In Potamotrygonocestus amazonensis, P. magdalenensis, and P. maurae the hook prong emerges from the middle of the handle. In the remaining species the prong emerges from the posterior end of the handle. The polarity for this character according to Pedibothrium would depend on a particular statement of homology between the single prong of Potamotrygonocestus and either the inner or outer hook prong of Pedibothrium. In Pedibothrium, the outer prong emerges from the middle of the base whereas the inner prong emerges from the posterior end (Fig. 12A). In Pachybothrium the hook prong emerges from the middle of the base (Fig. 12B). Thus, the polarity of the character is equivocal (outgroup state = ?). Character states: 0 = prong emerging from the posterior end of the handle; 1 = prong emerging from the middle of the handle. 2 Hook position in relation to bothridium. The bothridial hooks in P. amazonensis, P. magdalenensis, and P. maurae are



Table 4 Data matrix for six species of Potamotrygonocestus and six

morphological characters. Characters Taxa

1

2

3

4

5

6

Outgroup coding P. amazonensis P. magdalenensis P. maurae P. fitzgeraldae P. travassosi P. chaoi

? 1 1 1 0 0 0

? 1 1 1 0 0 0

0 0 0 0 1 1 1

0 2 2 0 1 1 0

0 1 1 1 1 1 0

0 1 1 0 1 1 1

attached approximately 10% of the bothridial length from the anterior end of the bothridia, while in the remaining species the hooks are attached approximately 30% of the bothridial length from the anterior end. Pedibothrium is polymorphic for this character. Pedibothrium globicephalum Linton, 1909 and P. lintoni Caira & Pritchard, 1986 have bothridial hooks at the anterior 25–30% of the bothridia, whereas P. maccallumi Caira & Pritchard, 1986 and P. brevispine Linton, 1909 have hooks close to the anterior end of the bothridia, similar to all other onchobothriids. In Pachybothrium, the hooks are at the anterior end of the bothridia in the centre of a muscular pad. It is difficult to postulate any robust statement of homology for this character. Thus, we consider the polarity equivocal for this character state. Character states: 0 = hooks attached approximately 30% of the bothridial length from the anterior end; 1 = hooks attached approximately 10% of the bothridial length from the anterior end. 3 Hook symmetry. The medial and lateral hooks in Potamotrygonocestus may be either symmetrical (as in P. amazonensis, P. magdalenensis, and P. maurae) or asymmetrical (as in P. chaoi, P. fitzgeraldae, and P. travassosi). In Pedibothrium and Pachybothrium the bothridial hooks are symmetrical, suggesting that asymmetrical hooks are derived within Potamotrygonocestus. Character states: 0 = hooks asymmetrical; 1 = hooks symmetrical. 4 Genital pore position. Potamotrygonocestus chaoi and P. maurae possess genital pores anterior to the ovarian isthmus at the level of the anterior end of the ovarian lobes. Potamotrygonocestus fitzgeraldae and P. travassosi have genital pores at the level of the ovarian isthmus or slightly anterior to it, whereas in the remaining species the genital pore is posterior to the isthmus. Both outgroup genera have preovarian genital pores. Thus, we consider genital pores anterior to the ovarian isthmus at the level of the anterior end of the ovarian lobes plesiomorphic within Potamotrygonocestus. Character states: 0 = genital pores anterior to the ovarian © The Norwegian Academy of Science and Letters • Zoologica Scripta, 32, 4, July 2003, pp367– 396

isthmus at the level of the anterior end of the ovarian lobes; 1 = genital pores at the level of the ovarian isthmus or slightly anterior to it; 2 = genital pores posterior to the isthmus. 5 Testes number. In Potamotrygonocestus, P. chaoi has a greater number of testes (64 –107) than other species of the genus, all of which have fewer than 60 testes. The number of testes in the outgroup ranges from as few as 80 in Pachybothrium hutsoni to as many as 291 in Pedibothrium globicephalum, suggesting that fewer testes is derived within Potamotrygonocestus. Character states: 0 = more than 60 testes per proglottid; 1 = fewer than 60 testes per proglottid. 6 Vitellaria distribution. Potamotrygonocestus maurae possess vitellaria extending to the posterior margin of the proglottid, whereas in the remaining species of Potamotrygonocestus the vitellaria only extend to the level of the ovarian isthmus. Both outgroup genera have vitellaria which extend to the posterior margin of the proglottid. This condition is considered plesiomorphic within Potamotrygonocestus. Character states: 0 = posterior end of the vitellaria extends to the posterior margin of the proglottid; 1 = posterior end of the vitellaria at the level of the ovarian isthmus. Phylogenetic analysis The phylogenetic analysis of six morphological characters for six species of Potamotrygonocestus generated a single tree eight steps long, with a consistency index of 0.87, a retention index of 0.90, and a rescaled consistency index of 0.79 (Fig. 13).

Discussion Taxonomic account The taxonomy of Potamotrygonocestus has suffered from inadequate sample sizes for respective species from which descriptions could take into account intra- and interpopulational variation. The majority of the species descriptions have been based on a small number of specimens from a single locality, usually from a single host species. In the present study, spiral valves were fixed in the field and then analysed in the laboratory, providing more specimens than previously available for study, although some populations were still poorly represented. Among the six species recognized in this study, two phenetic groupings can be distinguished. One grouping is represented by the clade comprising Potamotrygonocestus chaoi, P. fitzgeraldae, and P. travassosi, which can be recognized by possessing asymmetrical hooks at the anterior third to quarter of the bothridia, and prongs emerging from the posterior end of the handle (hereafter referred to as the P. travassosi group). The other grouping comprises the paraphyletic species P. amazonensis, P. magdalenensis and P. maurae, which have symmetrical hooks at the anterior 10th of the bothridia and prongs emerging from the middle of the handle (hereafter referred to as the P. magdalenensis group). 393


Fig. 13 Phylogenetic

hypothesis for six species of Potamotrygonocestus based on six morphological characters.

Within the P. travassosi group, P. fitzgeraldae might represent a species complex. As discussed in the remarks on P. fitzgeraldae, there are morphological differences between the populations of this species from Rio Negro and Rio Xingú as compared with those of the Paraná drainages. However, as mentioned above, the sample size for specimens from the Paraná drainages undermine any further conclusions on the taxonomic status of specimens collected from that basin. For the P. magdalenensis group, P. amazonensis might also represent a species complex. Specimens attributed to P. amazonensis from the Paraná drainage inhabiting Potamotrygon falkneri possess a cirrus sac approximately at the level of the ovarian isthmus (Fig. 3C), differing from the more posterior position for this structure found in specimens of the type series for P. amazonensis (Fig. 3A) and specimens from other localities such as Rio Negro and the Lower Amazon. In other species of Potamotrygonocestus, the position of the genital pore seems to be fairly consistent. However, because of the small number of specimens collected, no decision can be made on whether the patterns observed constitute interpopulational variation or are indicative of the inclusion of different species within the concept of P. amazonensis. Phylogeny of Potamotrygonocestus Brooks et al. (1981) used four characters to infer sister-group relationships for three species of Potamotrygonocestus [P. amazonensis, P. magdalenensis and P. travassosi (as P. orinocoensis)]: length of bothridial hook prongs [called ‘bothridial hook length’ by Brooks et al. (1981)], hook prong attachment, ovarian shape, and vitellaria configuration. Of those characters, only the hook prong attachment was considered herein. The 394

length of bothridial hook prongs was not included in our study because we found no gap among the ranges obtained for this parameter (see Tables 2 and 3). The ovarian shape was defined by Brooks et al. (1981) as having two states; inverted ‘A’, considered to be plesiomorphic, and ‘theta-shaped’, considered to be the derived state within Potamotrygonocestus. Our taxonomic account suggested that a ‘theta-shaped’ ovary may be dependent on the developmental stage of the proglottid. Specimens with a ‘theta-shaped’ ovary were observed in P. travassosi and P. fitzgeraldae. However, these species are polymorphic for the character. In accordance with Brooks et al. (1981), outgroup analysis suggests that the presence of a ‘thetashaped’ ovary is derived within the ingroup. Thus, if included in the analysis, this character would support the sister-group relationship between P. travassosi and P. fitzgeraldae, which herein was supported by the presence of genital pores anterior to the ovarian isthmus [character 4(1)]. For vitellarine configuration, Brooks et al. (1981) considered two character states: vitellaria follicular and compact. As discussed in the taxonomic account for Potamotrygonocestus, a follicular vitellarium is only observed in late development of the proglottid. Species of this genus usually possess compact vitellaria. Thus, we did not include this character in our analysis. Brooks et al. (1981) concluded that P. magdalenensis and P. travassosi were sister species (based on the presence of compact vitellaria), with P. amazonensis their sister species. The results of our analysis suggest that P. magdalenensis is the sister species of P. amazonensis, and that P. travassosi is the sister species of P. fitzgeraldae, which together are the sister group of P. chaoi (Fig. 13). The relationship between Potamotrygonocestus and other oncobothriids is the least known of the tetraphyllideans that



inhabit freshwater potamotrygonids. Species of Pachybothrium and Pedibothrium are parasites of orectolobiformes sharks. If these genera do, in fact, share a close common ancestor with Potamotrygonocestus, as the putative synapomorphies described above suggest [see also Caira et al. (1999)], it would imply that the ancestor of Potamotrygonocestus underwent a host switch from sharks to stingrays. There are three testable host switching scenarios: (i) the host switch occurred prior to the invasion of the ancestor of the potamotrygonids into South American river systems; (ii) the host switch occurred as a result of the invasion of sharks and the ancestor of potamotrygonids into South American river systems; and (iii) the host switch occurred after the invasion when the potamotrygonids were already established in the rivers of South America. The first hypothesis would be corroborated by finding a species of Potamotrygonocestus, or its sister group, inhabiting the marine sister group of potamotrygonids. The second hypothesis predicts that sharks hosting the ancestor of Potamotrygonocestus coexisted with potamotrygonids during their establishment in the fluvial systems of South America. The third hypothesis predicts that sharks coexisted with potamotrygonids after their establishment in the fluvial systems of South America. There is evidence that euryhaline bullsharks (Carcharhinus) were present in South America during the Late Miocene Seaway (Räsänen et al. 1995), but nothing resembling Potamotrygonocestus has been reported in bullsharks. Tests of these hypotheses must await further collections of Potamotrygonocestus as well as more extensive inventories of eucestodes of marine elasmobranchs. Small sample sizes and limited collections also limit generalization concerning distributional patterns and host specificity within Potamotrygonocestus. However, some patterns that deserve comment have emerged in our study. Potamotrygonocestus amazonensis, P. fitzgeraldae, and P. travassosi are widely distributed geographically and inhabit more than one species of freshwater potamotrygonid, a pattern that has been reported for other helminths inhabiting potamotrygonids (Brooks & Amato 1992; Brooks 1995; Marques 2000). In contrast, P. magdalenensis, P. maurae, and P. chaoi are only known to inhabit a single species of host (Potamotrygon magdalenensis, P. schroederi, and Plesiotrygon iwamae, respectively) from single localities (Rio Magdalena and Lower Solimões, respectively). Potamotrygonocestus magdalenensis inhabits Potamotrygon magdalenae, endemic to the Rio Magdalena, a river system that was isolated from other neotropical hydrographic basins by the uplift of the Andes, which may account for its restricted host and geographical range. Potamotrygonocestus maurae and P. chaoi, on the other hand, inhabit hosts that coexist with other species of freshwater potamotrygonids, but were collected in only a single host species. If their restricted geographical distribution and host range is not a sampling


artefact, then we must look beyond allopatry to trophic segregation among co-occurring and closely related hosts, or to some intrinsic aspect of the biology of the eucestode species themselves, for an explanation.

Acknowledgements We are indebted to Lisa Nodwell, Jaime Carvalho Junior, Labbish Chao and the staff and students of the Projeto Piaba, Barcelos, Amazonas, Brazil, for their assistance during the field work in the Amazon region. We are grateful for the hospitality of Maura Kumagay and her family to FPLM during his stay in Belém do Pará. We gratefully acknowledge Señores Lauriano Sanchez, Juan Sanchez, Hector Sanches, and Andres Gonzales for their help in Puerto Reconquista, Santa Fé, Argentina. This work could not be realized without the help of local fishermen from Argentina and the Amazon region to whom we express our gratitude. We thank Scott Monks and Anindo Choudhury for reviewing early versions of this manuscript. We are also thankful to Gerhard Pohle for allowing us to use his image analysis software. This work was financially supported by CNPq (Consenho Nacional de Desenvolvimento Científico e Tecnológico, Federal Government of Brazil) doctorate fellowship to FPLM and NSERC (Natural Sciences and Engineering Council of Canada) operating grant A7696 to DRB.

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