New data on the morphology and phylogenetic connections of Postlepidapedon opisthobifurcatum (Trematoda, Lepocreadioidea: Lepidapedidae), a parasite of Antarctic and sub-Antarctic fishes

Summary The trematode Postlepidapedon opisthobifurcatum (Zdzitowiecki, 1990) is a common intestinal parasite of the gadiform fishes of the Southern Ocean. In this work, we supplement the description of the species with the anatomy of the terminal part of the reproductive system and with molecular data. The male terminal genitalia are characterised by the presence of the external seminal vesicle and cirrus-sac. The external seminal vesicle is surrounded by aciniform groups of outer prostatic cells. Groups of outer prostatic cells and proximal parts of their ducts are associated with a thin-walled membrane that is connected to the proximal edge of the cirrus-sac. The cirrus-sac is claviform, with a long proximal part accommodating the tubular, thin-walled internal seminal vesicle and ducts of outer prostatic cells. The female terminal genitalia are represented by a thick-walled metraterm, which is surrounded by aciniform groups of glandular cells. Phylogenetic analysis based on 28S rDNA partial sequences data placed P. opisthobifurcatum into the monophyletic group Lepidapedidae, including the species Myzoxenus insolens (Crowcroft, 1945), Intusatrium robustum Durio et Manter, 1968, and Postlepidapedon uberis Bray, Cribb et Barker, 1997. However, we were unable to detect direct phylogenetic connections between P. opisthobifurcatum and P. uberis.

Description of Neolepidapedoides subantarcticus sp. nov. (Digenea, Lepocreadiidae) from sub-Antarctic notothenioid fishes

Neolepidapedoides subantarcticus sp. nov. (Digenea, Lepocreadiidae) is reported from the intestine, mainly the jejunum, of fishes in the eastern mouth of the Beagle Channel and in the harbour of Ushuaia in the Beagle Channel (Tierra del Fuego, Argentina) at a depth 7–30 m. The typical host is Patagonotothen longipes, other hosts are P. tessellata, P. brevicauda and Champsocephalus esox. The male terminal genitalia indicates that the new species belongs to the genus Neolepidapedoides (Lepocreadiidae, Lepocreadiinae). The most important taxonomic features are the presence of eye-spots, the spined tegument, the “Opechona-type” cirrus-sac, the external seminal vesicle free in the parenchyma, the gonads arranged in tandem, the vitelline follicles extending from the level of the oesophagus in the forebody to the posterior end of the body and an I-shaped excretory vesicle reaching to the intestinal bifurcation and the absence of a pseudoesophagus. Ten previously described species differ from the N. subantarcticus sp. nov. mainly in the extent of the vitelline fields and length of the excretory vesicle which reaches into forebody.

Observations on the Parorchis acanthus complex (Philophthalmidae: Parorchiinae) with the description of three new species of Parorchis Nicoll, 1907 and the replacement of the preoccupied junior homonym Paratrema Dronen & Badley, 1979 with Stenomesotrema nomen novum

A brief history of the genus Parorchis Nicoll, 1907 (Philophthalmidae: Parorchiinae) is provided along with the description of 3 new species: Parorchis catoptrophori n. sp., distinguished by a bipartite pharynx with a larger, anterior, muscular primary pharynx, followed by a smaller posterior nonmuscular secondary part composed of 2 smaller posterior extensions; Parorchis longivesiculus n. sp., distinguished by an external seminal vesicle that overreaches the acetabulum posteriorly, extending into the hindbody to about midway between the testes and the acetabulum; and Parorchis ralli n. sp., distinguished by an external seminal vesicle, the posterior third of which is tubular and coiled. The preoccupied junior homonym Paratrema Dronen & Badley, 1979 (Parorchiinae) is replaced by Stenomesotrema nomen novum, and a rediagnosis of the genus is given wherein Stenomesotrema numenii n. comb. is assigned as the type species in the genus, and Stenomesotrema asiaticus n. comb. is proposed as a second species in the genus. Species of Parorchis are divided into 2 basic body types. The first type contains those species with a barbell-like or hourglass body shape, a rudimentary head collar, symmetrical to tandem testes, 2 rows of corner spines on the head collar, a preequatorial acetabulum, and a forebody that is wider than the hindbody. The second body type, called the “Parorchis body type”, contains those species with a pyriform body shape, a well-developed head collar, symmetrical testes, a single continuous row of circumoral spines on the head collar, and an equatorial acetabulum. There appears to be 2 subtypes of the Parorchis body type: subtype 1 containing those species possessing smooth to slightly irregular testes (not deeply lobed) and an esophagus lacking diverticuli; and subtype 2 containing those species having irregular and deeply lobed testes and an esophagus possessing lateral diverticuli. A comparative analysis of museum-deposited specimens of P. acanthus revealed as many as 9 possible additional species of Parorchis. This suggests potential problems in using measurements of structures alone without differences in additional corroborating specific features to separate species of Parorchis. Along with measurements, the number and size of spines on the circumoral collar, the presence or absence of a prepharynx, an intertesticular space, and esophageal diverticula as well as the extent of the posttesticular space, the length of the metraterm, egg size and the ratios of the width of the oral sucker to the width of the acetabulum and the width of the pharynx to the width of the oral sucker appear useful in distinguishing species of Parorchis.

Trematodes from Red Sea fishes: Proneohelicometra aegyptensis gen. nov., sp. nov. (Opecoelidae Ozaki, 1925) and Neohypocreadium gibsoni sp. nov. (Lepocreadiidae Odhner, 1905)

Specimens of the fishes Pterois volitans Linnaeus (Scorpaenidae) and Chaetodon auriga Forsskål (Chaetodontidae) were caught in the Red Sea off the coast of Sharm El-Sheikh, South Sinai, Egypt. Five (20%) and 20 (44%) of these fishes, respectively, were found to harbour intestinal trematodes. P. volitans was parasitised by Proneohelicometra aegyptensis gen. nov., sp. nov. (Opecoelidae) and C. auriga by Neohypocreadium gibsoni sp. nov. (Lepocreadiidae). Proneohelicometra gen. nov. is similar to Neohelicometra Siddiqi et Cable, 1960 which is the only opecoelid genus having caeca opening with separate ani and eggs with unipolar filaments, but differs significantly from it in having two lateral folds of body wall extending along the posterior third of body, an oral sucker smaller than the ventral sucker, a median cirrus sac not reaching the ventral sucker posteriorly and a median genital pore situating immediately posterior to the intestinal bifurcation. Neohypocreadium gibsoni sp. nov. is similar to the other four species of the genus, but is unique in having a distinctly pear-shaped body and a much smaller egg size, and differs significantly from each in several other characters: from N. longisaccatum, it differs in having a cirrus sac not reaching the testes and a pretesticular ovary; from N. dorsoporum in having an external seminal vesicle much shorter than the cirrus sac, a longer cirrus sac extending posteriorly to the level of the posterior margin of the ventral sucker and a pretesticular ovary; from N. chaetodoni in having a smaller body size, symmetrical testes, a longer cirrus sac extending posteriorly to the level of the posterior margin of the ventral sucker and a trilobed ovary; and from N. aegyptense in having a smaller body size, symmetrical testes, a longer cirrus sac extending posteriorly to the level of the posterior margin of the ventral sucker, a trilobed ovary and vitelline follicles terminating anteriorly at the level of oesophagus. Neohypocreadium Machida et Uchida, 1987 is briefly reviewed.

Pearsonellum-Corventum, Gen-Nov Et Sp-Nov (Digenea, Sanguinicolidae), in Serranid Fishes From the Capricornia Section of the Great-Barrier-Reef

Pearsonellum corventum, gen. et sp. nov., is described from the heart of Plectropomus leopardus (type host), Epinephelus quoyanus, E. merra, and E. ongus from the vicinity of Heron I. in the Great Barrier Reef. It has body spines in ventrolateral transverse rows, an X-shaped intestine with long posterior caeca, a single testis, a unique auxillary external seminal vesicle, a well-developed cirrus sac, a post-testicular ovary, a partly preovarian uterus, and a well-developed metraterm. Those characteristics support a closer relationship among many piscine blood fluke genera than indicated by the seven subfamilies recognised in Yamaguti's 'Synopsis of Digenetic Trematodes of Vertebrates'.