Species Diversity

Dendrochirus tuamotuensis sp. nov. (Scorpaenidae: Pteroinae) is described on the basis of a single specimen collected off Makemo Atoll, Tuamotu Archipelago, South Pacific Ocean. The new species is uniquely characterized by having bilobed pectoral fins, those of its all congeners being rounded. The new species is similar to a Hawaiian endemic congener, Dendrochirus barberi (Steindachner, 1900), in having nine dorsal-fin soft rays, five anal-fin soft rays, relatively high counts (more than 18) of pectoral-fin rays, fewer than two tentacles on the snout tip, and no large, ocellated spot on the soft-rayed portion of the dorsal fin. However, the new species is clearly distinguished from D. barberi by having more pectoral-fin rays (19 in the former vs usually 18 in the latter), higher counts of spinous points on the suborbital ridge (14–16 vs 1–9) and pterotic spine (8 vs 1–5), a slightly shallower, narrower body [body depth and width 35.4% of SL and 18.6% of SL, respectively, vs 34.0–43.9 (mean 39.2)% of SL and 19.7–26.4 (22.7)% of SL], a slightly shorter, narrower head [head length and width, 37.6% of SL and 12.9% of SL, respectively, vs 40.3–45.7 (42.9)% of SL and 13.8–17.2 (15.4)% of SL], slightly smaller orbit diameter [12.9% of SL vs 13.1–16.0 (14.2)% of SL], and a slightly shorter postorbital length [15.3% of SL vs 16.4–20.6 (18.5)% of SL].

Eight specimens (33.2–40.8 mm standard length) of Helcogramma aquila Williams and McCormick, 1990 (Tripterygiidae), previously known from the Philippines and the Mariana Islands, were collected from Okinoerabu-jima and Okinawa-jima islands in the Ryukyu Islands, Japan. These specimens represent the first records of this species from Japan, and the specimen from Okinoerabu-jima island is the northernmost record for the species. Underwater photographs of male and female individuals and color photographs of a fresh male specimen are given for the first time for H. aquila.

Cladomyrma sirindhornae sp. nov. is described from eastern Thailand, based on the minor and major workers, queen and male. The colonies examined here nested inside branches of the climbing plant Sphenodesme involucrata (Presl) Robins. (Verbenaceae).

A new genus and new species of the hermit crab family Paguridae is described and illustrated on the basis of three specimens collected from off Balicasag Island, Bohol Sea, the Philippines. The new genus, Pliopagurus, is referred to the “Pylopagurus-Tomopagurus” group on account of its having 11 pairs of biserial gills and paired first pleopods in females, and appears closest to Lophopagurus McLaughlin, 1981. The possession of short sexual tubes on both coxae of the fifth pereopods in the male and the lack of a median crest or dorsolateral keel of the left chela distinguish Pliopagurus from Lophopagurus. An emended key to the genera of the “Pylopagurus-Tomopagurus” group is presented.

Aniculus erythraeus Forest, 1984, a poorly known species of hermit crab, is reported for the first time from Japan based on a single specimen collected from Kume Island, Ryukyu Islands. This discovery increases the number of Japanese species of Aniculus to seven and greatly extends the distributional range of the present species to the north. Differences between A. erythraeus and its close congener A. ursus (Olivier, 1812) are discussed on the basis of the specimens from the Ryukyu Islands.

The diogenid hermit crab taxon Dardanus watasei (Terao, 1913) has been suggested to be a possible junior synonym of D. scutellatus (H. Milne Edwards, 1848). Re-examination of the holotype and three additional specimens referred to the taxon Pagurus watasei by Terao himself, however, has shown that it is conspecific with Dardanus aspersus (Berthold, 1845), and consequently Pagurus watasei is placed in the synonymy of the latter species.

A new species of the ghost shrimp genus Ctenocheloides (Decapoda: Axiidea: Ctenochelidae), C. nomurai, is described on the basis of two male specimens from the shallow subtidal bottom of Arita Bay, Kushimoto, Wakayama Prefecture, Japan. The new species differs from its sole known congener, C. attenborougi Anker, 2010, in the structure of the carapace, the well developed crista dentata of the third maxilliped, the strongly asymmetrical chelipeds, and the chelate fifth pereopod. The two type specimens were found under a rock on soft bottom, suggesting that the new species is a burrower like other callianassoid species.

We sampled ostracods in Sarobetsu Marsh, Rishiri Rebun Sarobetsu National Park, Hokkaido, Japan, from April 2005 to November 2007 and identified four species: Cryptocandona sp., Pseudocandona tenuirostris sp. nov., Physocypria nipponica Okubo, 1990, and Metacypris digitiformis Smith and Hiruta, 2004. Cryptocandona sp. is similar to C. reducta (Alm, 1914) and C. brehmi (Klie, 1934), but positive identification is postponed due to the absence of male specimens. In having three setae in the setal group of the second segment of the mandibular palp, Pseudocandona tenuirostris sp. nov. belongs to the Ps. rostrata species group, and it is characterized by a beak-like medial lobe on the distal end of each hemipenis. From literature based information, Japanese populations of Physocypria nipponica and Ph. kraepelini from Europe have morphological differences at their hemipenis. We regard Ph. nipponica as a distinct species, even though this taxon has been suggested to be a synonym of Ph. kraepelini Müller, 1993. We discuss the seasonal prevalence of the four species detected.

The invertebrate fauna associated with floating Sargassum horneri (Turner) C. Agardh, 1820 in the East China Sea was investigated in terms of ecology and biogeography. Floating algal rafts consisting of only S. horneri were collected at 16 stations in the East China Sea during a cruise of research vessel (R/V) Tansei-Maru in February, 2011. A total of 53 rafts were obtained for faunal investigations at 14 of the 16 stations. In addition to fish eggs, 10 invertebrate taxa were found on the floating algae. Of the collected phytal animals, harpacticoid copepods were most abundant in terms of number (80%), followed by cirripedes (15%), amphipods (4%), and others (1%). The faunal diversity on the algae was correlated to the algal weight. The faunal diversity differed significantly between stations and was highest in the northernmost part of the East China Sea. Density and abundance of animals were highest in areas close to the Kuroshio Current. Considering the direction of flow of the Kuroshio Current and the density of cirripedes immigrating from the surrounding water onto the floating algae, most of the floating S. horneri possibly originated in the southern part of the East China Sea. On the other hand, the Sargassum rafts collected in the northernmost part of the East China Sea could have originated from the coast of eastern China. Most of the animals found on the floating Sargassum were pelagic taxa that complete their life cycles on the rafts in situ. Typical coastal animals, including gammaridean and caprellidean amphipods, tanaidaceans, nematodes, gastropods, polychaetes, halacarid mites, bryozoans, and hydrozoans, were also obtained from the floating Sargassum, but only occasionally and their densities were quite low. These facts suggest that dispersal events among benthic habitats via Sargassum rafts are relatively rare.

Seven new species of the subfamily Coelotinae are described from Kyushu, Japan, under the names Coelotes unzenensis sp. nov., C. saikaiensis sp. nov., C. koshikiensis sp. nov., C. iriei sp. nov., C. oxyacanthus sp. nov., Draconarius verrucifer sp. nov., and D. dialeptus sp. nov. Coelotes unzenensis sp. nov. and C. saikaiensis sp. nov. are unique in comparison with all the known Japanese coelotine spiders with two exceptions, Alloclubionoides grandivulva (Yaginuma, 1969) and C. motobuensis (Shimojana, 2000), in lacking the patellar apophysis of the male palpus. Coelotes koshikiensis sp. nov. has genital organs similar to those of C. gotoensis Okumura, 2007 and is endemic to the Koshiki Islands, Kagoshima Prefecture. Coelotes iriei sp. nov. has genital organs similar to those of C. decolor Nishikawa, 1973, and these two species are closely related. Coelotes oxyacanthus sp. nov. resembles C. hiradoensis Okumura and Ono, 2006. This new species is endemic to the Goto Islands, Nagasaki Prefecture. Draconarius verrucifer sp. nov. is distinguished from the other known coelotine spiders from Japan by having a small protrusion on the epigynum. Draconarius dialeptus sp. nov. is found only on Yaku Island, Kagoshima Prefecture. Its male palpal structure is similar to that of some other species of Draconarius, including D. aspinatus Wang, Yin, Peng, and Xie, 1990, D. bituberculatus Wang, Yin, Peng, and Xie, 1990, and D. venustus Ovtchinnikov, 1999. In this paper, D. verrucifer sp. nov. is described based only on females, D. dialeptus sp. nov. on males, and the other new species on both sexes.

Two specimens of the large, predaceous salifid leech Mimobdella japonica Blanchard, 1897 were collected from Okinawajima island, Ryukyu Islands, Japan, representing the first record of this species from Okinawajima. A description is provided of the external and internal morphology of these specimens and two additional specimens of M. japonica from Amami-oshima island, also in the Ryukyu Islands. COI sequences showed no difference between the two specimens of M. japonica from Okinawajima and the two specimens from Amami-oshima (K2P distance=0%). This suggests that M. japonica is an introduced species in one or both of these islands.

We describe a new species of capitellid polychaete, Mediomastus opertaculeus sp. nov., from an intertidal rocky shore in Hokkaido, northern Japan. This new species is distinguishable from all other 13 congeners by such characteristics as (1) staining pattern with methyl green (presumably indicating glandular cells in the epidermis), (2) absence of capillary chaetae in the abdomen, (3) absence of paddle-like chaetae in the thorax, and (4) shapes of the thoracic capillary chaetae and hooded hooks. Aligned partial sequences (624 bases) of cytochrome c oxidase subunit I gene from four paratypes of M. opertaculeus differed at 1–4 sites, corresponding to Kimura two-parameter (K2P) distances of 0.002–0.006. K2P distances were 0.216–0.218 between our sequences and that from an unidentified Mediomastus sp. from Darwin Harbor, Australia, indicating these are not conspecific.

Five species of the soft-coral genus Dendronephthya from Japanese waters are redescribed based on the type specimens deposited in the Naturhistorisches Museum der Burgergemeinde Bern: D. doederleini Kükenthal, 1905, D. punicea (Studer, 1888), D. flabellifera (Studer, 1888), D. pumilio (Studer, 1888), and D. rigida (Studer, 1888). These specimens were collected by the German zoologist Ludwig Döderlein between 1879 and 1881 during his stay in Japan. Several other specimens ascribed to these species by later authors and deposited in natural history museums in Europe and the U.S.A. were also examined in the present study; some of those are considered to have been misidentified.