First Record of Elasmobranch Hosts for the Gnathiid Isopod Crustacean Thaumastognathia: Description of Thaumastognathia bicorniger sp. nov.

Gnathiid larvae (Crustacea; Isopoda; Gnathiidae) infesting elasmobranch and holocephalan fishes from mainly bathyal depths off Suruga Bay, off Kume-jima Island, and five sites from off Tokyo Bay to Shimoda City, Japan were examined. A total of 1460 gnathiid larvae were sampled from 87 host individuals belonging to seven families and 10 species. The morphology of these larvae was distinguishable from other gnathiid species by the head appendages. These larvae presented two pigmentation patterns, stripes or spots, on their dorsal thoraxes in live specimens. Furthermore, they were determined as the second and third stage praniza larvae on the basis of allometric variance of maximum head and abdomen widths. A third stage praniza with stripe pigmentation metamorphosed into an adult male and could be identified as a new species of the genus Thaumastognathia Monod, 1926. The duration between detachment from the host and metamorphosis into male adult required 204 days. This paper describes Thaumastognathia bicorniger sp. nov. on the basis of P3/stripe larvae and the male adult. This report is the first record of the larva and host information for a species of Thaumastognathia.

DNA barcoding and morphological analyses revealed validity of Diadema clarki Ikeda, 1939 (Echinodermata, Echinoidea, Diadematidae).

A long-spined sea urchin Diadema-sp reported from Japanese waters was genetically distinct from all known Diadema species, but it remained undescribed. Extensive field surveys in Japan with molecular identification performed in the present study determined five phenotypes (I to V) in Diadema-sp according to the presence and/or shape of a white streak and blue iridophore lines in the naked space of the interambulacral area. All phenotypes were distinct from Diadema setosum (Leske, 1778) and Diadema savignyi (Audouin, 1829), of which a major type (I) corresponded to Diadema clarki Ikeda, 1939 that was questioned and synonymized with Diadema setosum by Mortensen (1940). The holotype of Diadema clarki has not been found, but three unlabeled dried tests of Diadema were found among Ikeda's original collection held in the Kitakyushu Museum of Natural History and Human History, Fukuoka, Japan. A short mtDNA COI fragment (ca. 350bp) was amplified from one of the tests, and the nucleotide sequence determined (275bp) was nearly identical with that of Diadema-sp. Arrangements of the primary tubercles on the coronal plates in Diadema-sp and the museum specimen also conformed with Diadema clarki, indicating that Diadema-sp is identical to Diadema clarki and a valid species. Narrow latitudinal distribution (31°N to 35°N) of Diadema clarki in Japan was observed, where it co-existed with abundant Diadema setosum and rare Diadema savignyi. No Diadema clarki was found in the southern islands in Japan, such as Satsunan Islands to Ryukyu Islands and Ogasawara Island, where Diadema setosum and Diadema savignyi were commonly observed.

Three new species of Pseudodactylogyrus (Monogenea: Pseudodactylogyridae) from Australian eels.

Three species of Pseudodactylogyrus Gusev, 1965 (Monogenea: Pseudodactylogyridae) were collected from the gills of Anguilla reinhardtii Steindachner and A. australis Richardson from several localities in Australia and eels imported to Japan from Australia. Pseudodactylogyrus gusevi sp. n. from A. reinhardtii (type host) and A. australis in Queensland, Australia is most similar to P. bini (Kikuchi, 1929), but can be differentiated by the shorter male copulatory tube, heavy sclerotisation of the vaginal tube and the presence of a small projection of the supplementary piece of the hamulus. Pseudodactylogyrus rohdei sp. n. from A. australis (type host) in Queensland, Australia is most similar to P. anguillae (Yin et Sproston, 1948), but differs in the possession of a longer cement gland and the presence of a small projection on the supplementary piece of the hamulus. Pseudodactylogyrus bini sensu Gusev, 1965 and P. anguillae sensu Gusev, 1965 are synonymised with P. gusevi sp. n. and P. rohdei sp. n., respectively. Pseudodactylogyrus mundayi sp. n. from A. australis, originating in Tasmania, Australia and sent alive to Japan, is most similar to P. kamegaii Iwashita, Hirata et Ogawa, 2002, from which it can be discriminated by the shorter male copulatory tube and the shorter vaginal tube. Dactylogyrus bialatus Wu, Wang et Jian, 1988 from Synechogobius ommaturus (Richardson) (Gobiidae) is transferred to Pseudodactylogyrus as P. bialatus comb. n. A phylogenetic tree based on the ITS2 region of six species of Pseudodactylogyrus including P. gusevi and P. mundayi shows that P. haze from a goby diverged first, and that species from eels are monophyletic, forming three lineages differing by their zoogeographical distribution. With the three new species and one new combination proposed in this paper, Pseudodactylogyrus is now comprised of eight species infecting anguillid and gobiid fish, and a key to species is presented.

A new combination and a new species of onchobothriid tapeworm (Cestoda: Tetraphyllidea: Onchobothriidae) from triakid sharks.

A new combination and a new species of onchobothriid tapeworm are described from triakid sharks. We found Platybothrium xiamenensis Wang & Yang, 2001 and Erudituncus musteli (Yamaguti, 1952) from Hemitriakis japanica (Müller & Henle). Based on the morphology of the hooks P. xiamenensis is transferred to the genus Erudituncus Healy, Scholz & Caira, 2001. The specimens studied by us differ from the original description in the number of proglottids and testes and in the size of the cirrus-sac. However, we consider them conspecific with E. xiamenensis due to the consistent hook morphology and laciniations in both descriptions and believe the differences reflect intraspecific variation. The type-host of E. xiamenensis was reported as Mustelus griseus Pietschmann. However, in the present study, this parasite was found only in H. japanica and never in M. griseus although many specimens of the latter host were examined. This suggests that the type-host in the original description has probably been misidentified. We found another undescribed species in M. griseus, Calliobothrium shirozame n. sp., which is distinguished from the congeners by having a unique combination of the number of laciniations: four in the cephalic peduncle, six in the immature proglottids and four in the mature proglottids.

A new species of Calicotyle Diesing, 1850 (Monogenea: Monocotylidae) from the shortspine spurdog Squalus mitsukurii Jordan & Snyder and the synonymy of Gymnocalicotyle Nybelin, 1941 with this genus.

Calicotyle japonica n. sp., collected from the uterus, rectal gland, archinephric duct and cloaca of the shortspine spurdog Squalus mitsukurii Jordan & Snyder (Squaliformes) off the Pacific coast of Japan, is described. The new species can be distinguished from C. inermis Woolcock, 1936 by the shape of the male copulatory organ; in C. japonica this is directed anteriorly, is sharply bent in the middle and then increases in width toward the tip, whereas it is long, coiled and uniform in width throughout its entire length in C. inermis. Furthermore, the intestinal caeca have many irregular diverticula on both sides and the vaginal apertures are at the level of the common genital pore in C. japonica, whereas in C. inermis the intestine is smooth and the vaginae open at the level of the oötype. A phylogeny constructed using LSU rDNA data indicates that the new species is grouped with other Calicotyle species; based on this, Gymnocalicotyle Nybelin, 1941 is synonymised with Calicotyle Diesing, 1850. Calicotyle is divided into two major clades, with the new species being grouped with Calicotyle species infecting sharks and the second clade consisting of Calicotyle spp. infecting rays. This suggests that the loss of the hamuli in C. japonica and C. inermis, both parasites of sharks, is a comparatively recent event in the evolution of the genus.