Systematic status and first description of male of

SystematicParasitology 33: 143-148,1996. © 1996KluwerAcademicPublishers. Printedin the Netherlands.

143

Systematic status and first description of male of Dujardinia cenotae Pearse, 1936 [= Hysterothylacium cenotae (Pearse, 1936) Moravec et al., 1995] (Nematoda: Anisakidae) F r a n t i ~ e k M o r a v e c 1,2, Tom~i~ S c h o l z 1'2, C l a r a V i v a s - R o d r f g u e z 1, J o a q u i n V a r g a s - V ~ i z q u e z 1 a n d Edgar Mendoza-Franco 1

1Laboratory of Parasitology, Centre for Research and Advanced Studies, National Polytechnic Institute (CINVESTAV- IPN), Carr. Ant. a Progreso Km 6, AP 73 "Cordemex", CP 973 10 M~rida, Yucat6n, Mexico 2Institute of Parasitology, Academy of Sciences of the Czech Republic, Branigovsk6 31,370 05 ~esk~ Bud#jovice, Czech Republic Acceptedfor publication 12th September 1995

Abstract A new collection of adult anisakid nematodes from the intestine of the catfish Rhamdia guatemalensis from two cenotes (= sinkholes) and a cave in the Yucatan Peninsula, southeastern Mexico, has shown that they are conspecific with those inadequately described as Dujardinia cenotae Pearse, 1936. The female is redescribed and the male is described for the first time. The morphology of this species shows that it belongs to the genus Hysterothylacium. This is the only Hysterothylacium species recorded from freshwater fishes in Mexico and it may well be endemic to cenotes and caves of the Yucatan Peninsula. Introduction In 1936, Pearse described Dujardinia cenotae from four female specimens collected from the pimelodid catfish Rhamdia guatemalensis decolor from a cave and a cenote (= sinkhole) in Yucatan, Mexico. It has not been found since. The species description is too inadequate for any conclusions as to whether these nematodes were correctly identified (Sprent, 1990). Nevertheless, Dujardinia cenotae was later transferred by Baylis (1947) to the genus Dujardinascaris Baylis, 1927, where it has been listed in the recent checklist of ascaridoid parasites from fish hosts published by Bruce et al. (1994). In 1993 and 1994, during investigations into the helminth fauna of fish in cenotes (sinkholes) and caves of the Peninsula of Yucatan, southeastern Mexico, carried out by the team of the Laboratory of Parasitology, Centre for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV IPN) in M6rida, nematodes morphologically very similar to those described by Pearse (1936) as Dujardinia cenotae were recorded from the intestine of Rhamdia guatemalensis; these are considered to be conspecif-

ic with D. cenotae. The same adult nematodes have already been mentioned, under the name Hysterothylacium cenotae, in the paper by Moravec et al. (1995a) (the present paper was supposed to appear earlier), but no data on their morphology and taxonomy were provided. Therefore, this species is redescribed and its systematic status is discussed below.

Materials and methods The adult nematodes were collected from the intestine of the catfish Rhamdia guatemalensis originating from three localities in the Peninsula of Yucatan (States of Yucatan and Quintana Roo), southeastern Mexico. The fish were caught by angling and were carried alive to the laboratory in M6rida where they were killed and examined for parasites. The nematodes were fixed in hot 4% formaldehyde and cleared in glycerine for examination. After examination the specimens were preserved in 70% ethanol. Drawings were made with the aid of a Zeiss microscope drawing attachment. For scanning microscopy, the nematodes were dehydrated through an ethanol series and acetone, then subjected

144 to critical point drying. The specimens were coated with gold and examined with a JSM-6300 scanning electron microscope at an accelerating voltage of 15 kV. All measurements are given in millimetres. The specimens are deposited at the Institute of Parasitology, Academy of Sciences of the Czech Republic, (~esk6 Bud~jovice (Cat. No. N-660) and at the Biological Institute, National Autonomous University of Mexico, Mexico City.

Hysterothylacium cenotae (Pearse, 1936) Moravec et aL, 1995 (Figs 1,2) Syns: Dujardinia cenotae Pearse, 1936; Dujardinascaris cenotae (Pearse, 1936) Baylis, 1947. Description

Medium-sized, brownish nematodes with almost smooth cuticle; sometimes cuticle with fine, dense, transverse striations. Lateral alae absent. Anterior end with 3 lips almost equal in size; their flanges widest near posterior part of labial border. Dorsal lip with 2 lateral double papillae; subventral lips with amphid, adjacent medio-lateral double papilla and single lateral papilla. Interlabia small, their width at base slightly greater than height; interlabial grooves lacking. Oesophagus long, of almost uniform width. Nerve-ring encircling oesophagus approximately at border of first and second eighths of its length. Ventriculus present; oval; approximately as wide as oesophagus, usually slightly longer than wide; ventricular appendix narrow, relatively long. Excretory pore slightly posterior to level of nerve-ring. Two small round glands with broad ducts leading to base of lips present near anterior end of oesophagus (Fig. 1B). Intestinal caecum present; much shorter than ventricular appendix. Rectum a hyaline tube surrounded by 3 large, unicellular rectal glands. Tail conical; its tip with dense covering of minute spinous structures. Male. (Based on 2 specimens; measurements of one juvenile specimen in parentheses). Body 13.55 (7.98) long; maximum width 0.300 (0.177). Length of lips 0.075 (0.051). Oesophagus 3.00 (1.39) long. Nerve-ring and excretory pore 0.450 (0.340) and 0.525 (0.381), respectively, from anterior extremity. Ventriculus 0.140 (0.068) x 0.140 (0.082); ventricular appendix 1.51 (0.952) long. Intestinal caecum 0.815 (0.408). Length ratio of caecum and ventricular appendix 1:1.9 (1:2.3). Spicules equal, 0.210 (0.138)

long and 0.023 (0.018) wide, representing 1.5 (1.7)% of body length. Gubernaculum absent. Caudal papillae 27 pairs; 20 pairs pre-anal and 7 pairs post-anal (not established in juvenile). Tail 0.175 (0.147) long. Female. (Based on 3 gravid specimens). Length of body 22.17-25.13; maximum width 0.476~3.612. Length of lips 0.075--O.122. Interlabia 0.027 long. Length of oesophagus 3.60-3.62. Nerve-ring and excretory pore 0.517-0.653 and 0.558-0.680, respectively, from anterior extremity. Ventriculus 0.1900.204 x 0.177; ventricular appendix 2.24, width 0.177. Length of intestinal caecum 0.830--0.938, width 0.136. Length ratio of caecum and ventricular appendage 1:2.4. Vulva slit-like, near middle of body (slightly pre- or post-equatorial), 10.03-13.33 from anterior end of body. Vagina muscular, directed posteriorly. Uteri opposed. Eggs oval, thin-shelled smooth, nonembryonated; eggs 0.060-0.066 x 0.042. Tail 0.272 long; its tip 0.041-0.054 in length. Phasmids not located. Host: Rhamdia guatemalensis (GUnther) (Pimelodidae, Siluriformes). Site of infection: Intestine. Localities: Xmucuy Cenote (Zona Sotuta), State of Yucatan (26 October and 16 November, 1993; 25 July, 1994); Kawash Cenote (Zona centro), State of Quintana Roo (6 September, 1994); Cave Nohoch near Tulum, Q. Roo (15 October, 1994). Prevalence and intensity: Xmucuy - 6 of 21 fishes examined, intensity 1-4 nematodes; Kawash - 1 of 2, intensity 2; Nohoch - 1 of 1, intensity 2.

Discussion Based on its general morphology, this species clearly belongs to the anisakid genus Hysterothylacium Ward & Magath, 1917, as redefined by Deardorff & Overstreet ( 1981). Numerous species of this genus are parasitic as adults in marine, estuarine and freshwater fishes (Bruce et al., 1994). In 1936, Pearse described similar nematodes from Rhamdia guatemalensis decolor from San B ulha Cave, Motul, and from Ciruak Cenote, Chichen, both in Yucatan, Mexico, which he named Dujardinia cenotae. His description is poor, based only on a few females, and this species has not been recorded since. The morphology and measurements ofD. cenotae are approximately the same as those of female specimens of the

145

D

B

1

0.2

!:

G

E

H

t

J

I

I

0.1

I

Fig. 1. Hysterothylacium cenotae (Pearse, 1936). A, anterior part of body of female; B, head region; C, D, cephalic extremity, ventral and dorsal views; E, region of vulva; F, caudal region of male; G, tail region of female; H, tip of male tail; I, posterior region of male; J, tip of female tail; K, egg. Scale-bars in millimetres.

146

Fig. 2. Hysterothylacium cenotae (Pearse, 1936), SEM micrographs of cephalic extremity. A, dorsal lip; B, ventro-lateral lip; C, interlabium

between subventral lips; D, cephalic extremity, apical view of lips. a, amphid; d, double papilla; dl, dorsal lip; i, interlabium s, single papilla; vl, ventro-lateral lip.

present material, except for the alleged absence of the ventricular appendix in D. cenotae. However, the ventricular appendix is sometimes difficult to observe in the specimens of the present material and, apparently,

this was overlooked by Pearse (1936) while describing D. cenotae. Both the intestinal caecum and the ven-

tricular appendix were often overlooked in congeneric nematodes in the past [e.g. the original description

147 of Thynnascaris by Dollfus (1933) and the original description of Hysterothylacium by Ward & Magath (1917)]. On the basis of this observation, Pearse (1936) assigned his specimens to the genus Dujardinia Gedoelst, 1916 (a synonym of Dujardinascaris Baylis, 1927). Both D. cenotae and our nematodes were found in the same host species, Rhamdia guatemalensis, from the same habitats in the same geographical region (cenotes in Yucatan) and, therefore, we consider them identical. Our opinion that Pearse's (1936) nematodes did not belong to Dujardinia (= Dujardinascaris) but to Hysterothylacium is also supported by the fact that species once considered as members of Dujardinia (now belonging to Dujardinascaris, Multicaecum Baylis, 1923 and Paradujardinia Travassos, 1933 - see Hartwich, 1974) include nematodes parasitic as adults mainly in crocodilians and sirenians, whereas the hosts of the latter are fishes. Consequently, on the basis of newly obtained data on the morphology of this species, it is clear that it belongs to the genus Hysterothylacium. The new combination Hysterothylacium cenotae has already been used in the paper by Moravec et al. (1995a), based on the same material ( see ' Introduction'). On comparing this species with other congeners, H. cenotae shows some remarkable morphological features, being characterised mainly by unusually short spicules, the absence of lateral alae and the structure of the tail. Only three Hysterothylacium species have been previously recorded from freshwater fishes of North America (Rye & Baker, 1984): H. brachyurum Ward & Magath, 1917 from centrarchid fishes (Ambloplites, Lepomis, Micropterus), H. analarum Rye & Baker, 1984 from the centrarchid Lepomis gibbosus, and H. dollfusi (Schmidt, Leiby & Kritsky, 1974) from the polyodontid Polyodon spathula. All these species differ markedly from H. cenotae [H. brachyurum in possessing broad lateral alae; both H. analarum and H. dollfusi mainly in having much longer spicules (0.4500.625 mm and 1.07-1.45 mm, respectively, versus 0.210 mm in H. cenotae)]. Until recently, no Hysterothylacium species has been described from South and Central American freshwater fishes, although Petter (1995) has reported an unidentified Hysterothylacium fourth-stage larva from the doradid catfish Pterodoras costatus from Paraguay and Moravec et al. (1993) have recorded third-stage larvae of Hysterothylacium from a variety of freshwater fishes of different families from the Paran,'i River in Brazil.

Only in 1995 did Brizzola & Tanzola describe a new species, Hysterothylacium rhamdiae, from the intestine ofRhamdia sapo from Argentina. By its morphology and measurements, this species is very similar to H. cenotae, differing distinctly from the latter in the presence of narrow lateral alae and in the shape of lips. The spicules of both species are the smallest in the genus. H. cenotae is the first species of this genus recorded from freshwater fishes in Mexico and existing data indicate that it may well be endemic in cenotes and caves of the Yucatan Peninsula. The fact that H. cenotae is closely related toll. rhamdiae from a congeneric fish from Argentina supports the view of Moravec et al. (1995a), who consider the nematode fauna of freshwater fishes in Yucatan to be typically Neotropical. The biology of this nematode is not known. The life-cycles of some other Hysterothylacium species involve various invertebrates (mostly shrimps) as intermediate hosts, while different teleosts usually serve as paratenic hosts (Anderson, 1992; Moravec, 1994). Encysted third-stage larvae ofH. cenotae have recently been described from the abdominal cavity of the American eel Anguilla rostrata from cenotes in Quintana Roo, southeastern Mexico (Moravec et al., 1995b).

Acknowledgements The authors' thanks are due to the staff of the Laboratory of Electron Microscopy of the Institute of Parasitology, AS CR, in Cesk6 Bud~jovice, for their technical assistance. This study was supported by the grant no. P099 from the Comisi6n Nacional para el Conocimiento y Uso de la Biodiversidad (CONABIO), Mexico.

References Anderson, R.C. (1992) Nematode parasites of vertebrates. Their development and transmission. Wallingford: CAB International, 578 pp. Baylis, H.A. (1947) The nematode genus Dujardinascaris (nom. nov. pro Dujardinia) in Crocodilia, with a description of a new species. Annals and Magazine of Natural History, Ser. 11, 14, 123-134. Brizzola, S.M. & Tanzola, R.D. (1995) Hysterothylacium rhamdiae sp. n. (Ascaridoidea: Anisakidae) from a Neotropical catfish, Rhamdia sapo (Pisces: Pimelodidae). Mem6rias do lnstituto Oswaldo Cruz, 90, 349-352. Bruce, N.L., Adlard, R.D. & Cannon, L.R.G. (1994) Synoptic checklist of ascaridoid parasites (Nematoda) from fish hosts. Invertebrate Taxonomy, 8, 583-674.

148 Deardorff, T.L. & Overstreet, R.M. (1981)Review of Hysterothylacium and lheringascaris (both previously = Thynnascaris) (Nematoda: Anisakidae) from the northern Gulf of Mexico. Proceedings of the Biological Society of Washington, 93, 1035-1079. Dollfus. R.Ph. (1933) Thynnascaris legendrei n. gen., n. sp. de l'estomac du germon, Germo alalonga (Gmel.). Bulletin de la Soci~t~ Zoologique de France, 58, 7-13. Hartwich, G. (1974) Keys to genera of the Ascaridoidea. In: Anderson, R.C., Chabaud, A.G. & Willmott S. (Eds). CIH keys to the nematodeparasites of vertebrates. No. 2. Famham Royal, Bucks: Commonwealth Agricultural Bureaux, 15 pp. Moravec E (1994) Parasitic nematodes of freshwater fishes of Europe. Prague and Dordrecht: Academia and Kluwer Academic Publishers, 473 pp. Moravec, E, Kohn, A. & Feroandes, B.M.M. (1993) Nematode parasites of fishes of the Paran~i River, Brazil. Part 2. Seuratoidea, Ascaridoidea, Habronematoidea and Acuarioidea. Folia Parasitologica, 40, 115-134. Moravec, E, Vivas-Rodrfguez, C., Scholz, T., Vargas-V~izquez, J., Mendoza-Franco, E. & Gonz~ilez-Solis, D. (1995a) Nematodes parasitic in fishes of cenotes (= sinkholes) of the Peninsula of Yucatan, Mexico. Part 1. Adults. Folia Parasitologica, 42, 115129.

Moravec, E, Vivas-Rodriguez, C., Scholz, T., Vargas-V~tzquez, J., Mendosa-Franco, E., Schmitter-Soto, J.J. & Gonz~ilez-Solfs D. (1995b) Nematodes parasitic in fishes of cenotes (= sinkholes) of the Peninsula of Yucatan, Mexico. Part 2. Larvae. Folia Parasitologica, 42, 201-212. Pearse, A.S. (1936) Parasites from Yucatan. Carnegie Institute of Washington Publications, 457, 45-59. Petter A.J. (1995) Nematodes de poissons du Paraguay. VIII. Habronematoidea, Dracunculoidea et Ascaridoidea. Revue Suisse de Zoologie, 102, 89-102. Rye, L.A. & Baker, M.R. (1934) Hysterothylacium analarum n. sp. (Nematoda: Anisakidae) from pumpkinseed, Lepomis gibbosus (Linnaeus), in southern Ontario. Canadian Journal of Zoology, 62, 2307-2312. Sprent, LEA. (1990) Some ascaridoid nematodes of fishes: Heterrocheilinae. Systematic Parasitology, 16, 149-161. Ward, H.B, & Magath, T.B. (1917) Notes on some nematodes from freshwater fishes. Journal of Parasitalogy, 3, 57-65.