Tormopsolus attenuatus n. sp. (Digenea: Acanthocolpidae) from ...

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Abstract. A new acanthocolpid, Tormopsolus attenuatus n. sp., is described from the carangid Seriola hippos from waters off the coast of SW Australia. A cladistic ...

Systematic Parasitology 50: 91–99, 2001. © 2001 Kluwer Academic Publishers. Printed in the Netherlands.

91

Tormopsolus attenuatus n. sp. (Digenea: Acanthocolpidae) from Seriola hippos (Perciformes: Carangidae), Western Australia, with some observations on the relationships in the genus Rodney A. Bray1 & Thomas H. Cribb2 1 Department 2 Department

of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK of Parasitology, The University of Queensland, Brisbane, Queensland 4072, Australia

Accepted for publication 9th January, 2001

Abstract A new acanthocolpid, Tormopsolus attenuatus n. sp., is described from the carangid Seriola hippos from waters off the coast of SW Australia. A cladistic analysis of the genus using 31 morphological and metrical characters indicates that the closest species is T. asiatica Parukhin, 1976 status amend. (previously T. orientalis asiatica). T. attenuatus differs from T. asiatica in its smaller overall dimensions, more attenuated outline, relatively shorter post-testicular region, vitelline interruption at the level of the ovary, papillae on the oral sucker and, possibly, much longer genital atrium. Other similar species, T. orientalis Yamaguti, 1934 and T. medius Reimer, 1983, differ in having interruptions of the vitelline fields at the level of both testes and at the level of the ovary.

Introduction

Materials and methods

The genus Tormopsolus was erected by Poche (1926) for Distoma osculatum Looss, 1901 from Gaidropsarus [= Motella] vulgaris from Trieste. Looss (1901) had recognised the affinity of D. osculatum to the acanthocolpid genus Stephanostomum Looss, 1899 [= Stephanochasmus Looss, 1901]. In fact, Tormopsolus is very similar to Stephanostomum, being distinguished by the lack of the double row of enlarged circum-oral spines. Fourteen nominal species are mentioned in the literature, of which ten continue to be recognised as valid members of this genus. Most species are reported from carangid fishes. This paper includes the description of Tormopsolus attenuatus n. sp. from Seriola hippos in the south-eastern Indian Ocean. The new species is compared with existing species of Tormopsolus by a phylogenetic analysis of morphometric characters. It should be noted that the host of T. attenuatus, Seriola hippos Günther, is not synonymous with Caranx hippos (Linnaeus), being a species endemic to the waters around Australia, Norfolk Island and New Zealand.

Digeneans collected from freshly killed fish were fixed by being pipetted into nearly boiling saline and immediately preserved in formalin or 70% ethanol. Whole-mounts were stained with Mayer’s haematoxylin, cleared in methyl salicylate and mounted in Canada balsam. Measurements were made through a drawing tube on an Olympus BH-2 microscope, using a Digicad Plus digitising tablet and Carl Zeiss KS100 software adapted by Imaging Associates, and are quoted in micrometres. The following abbreviations are used: BMNH, the British Museum (Natural History) collection at The Natural History Museum, London, UK; QM, Queensland Museum collection, Brisbane, Australia. Phylogenetic trees and character evolution were inferred using PAUP (Swofford, 1993) and MacClade (Maddison & Maddison, 1992).

92 Family Acanthocolpidae Lühe, 1906 Genus Tormopsolus Poche, 1926

Tormopsolus attenuatus n. sp. Material studied ex Seriola hippos Günther (Carangidae). Intestine and stomach. Off Rottnest Island, Western Australia (32◦01 S, 115◦ 28 E; Dec., 1994). QM holotype G 217761, paratype G 217762, BMNH paratype 2001.1.4.17. Description (Figures 1-4) Based on 3 specimens, one with posterior extremity missing (measurements taken from all 3 but means given only for dimensions or ratios available on 3 specimens). Body attenuated, widest in region of ventral sucker and post-testicular region, 7,640-10,012 long × 382-415 (396) wide; maximum width 4.15.0% body length but most of body narrower (Figure 1). Eye-spot pigment in distinct patches lateral to prepharynx. Tegument with closely packed rows of large scale-like spines on lateral and dorsal surface of forebody, reducing in size posteriorly; no spines on ventral surface of forebody; at about level of ventral sucker spines are smaller, acicular and not in regular rows; spines in hindbody acicular, tiny, scattered, disappear at about level of ovary or anterior testes; no enlarged circum-oral spines. Oral sucker subterminal or virtually terminal, slightly embedded, with spinose tegument covering surface apart from narrow patches alongside longitudinally elongate aperture, with pair of distinct ventral-lateral muscular protuberances (papillae), not covered with spines (Figure 2), 179-186 × 199-201 (182 × 200). Ventral sucker subglobular, with antero-ventrally directed aperture, with unarmed marginal zone, 294-315 × 276-327 (305 × 309). Sucker-width ratio 1.4-1.6 (1.5). Forebody short, 537-559, 5.6-7.0% of body length. Prepharynx relatively long, 161-215 (192). Pharynx oval, often oriented obliquely to ventral surface; 123147 × 108-120 (133 × 115). Oesophagus apparently absent or short,

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