Nine species of patellogastropod limpets belonging to three families and four genera and two additional undescribed species are distributed in West Java, Indonesia. We formally name these two Patelloida species herein, based on shell and anatomical characters.
A new seguenziid gastropod, Basilissopsis hakuhoae, is described from 5473-5762 m depths of the oceanward slopes of the Japan and Kurile Trenches, western North Pacific Ocean. This new species is characterized by its large trochiform shell with a shoulder spiral, a bicarinate periphery, and secondary spiral riblets crossing with sigmoidal axial riblets allover the shell surface. Because the combination of these shell characters would be unique in Seguenziidae, the generic placement of this new species is by no means definitive.
A new species of the fasciolariid genus Fusinus is described from off Phuket Island, Thailand and from the Andaman and Nicobar Islands. It is compared with F. malhaensis Hadorn et al., 2001, F. colus (Linnaeus, 1758), F. crassiplicatus Kira, 1959 and F. laviniae Snyder & Hadorn, 2006, as well as some fossil species. Post-larval shell growth in the new species is divided into three clear phases.
Satsuma (Luchuhadra) largillierti is an arboreal land snail endemic to Okinawa Island, Japan, and its extensive geographic variation in shell morphology has long caused taxonomic confusion. A recent molecular phylogenetic study demonstrated that S. largillierti and the two species endemic to Okinoerabu Island, S. erabuensis and S. sooi, are more correctly re-organized into two species that are anatomically and genetically distinct. To confirm the taxonomic status and nomenclature of these species, we examined the available type materials and corresponding descriptions. We suggest that the above species be treated as S. eucosmia and S. largillierti, that S. sooi become a synonym of S. largillierti, and that S. erabuensis is reduced to a subspecies of S. eucosmia. We also present revised morphological descriptions of the four Luchuhadra species that range from Iheya Island off Okinawa Island to the Miyako Islands, which are here confirmed as distinct based on both morphological and molecular data.
At Olango Island, near Cebu, the Philippines, Salpocola philippinensis, new genus, lives attached to the burrowing sipunculan Sipunculus nudus. Only singly attached females were found. The gills represented by the inner demibranchs are heavily plicate, the visceral mass bears many lateral branching protrusions containing ovary and digestive gland diverticulae, and the protractor pedis muscle runs through the anterior adductor. A ciliated tube connects the infra- and suprabranchial chambers. Seminal receptacles are absent. The nature of sperm-containing bodies grafted upon the gills is discussed.
The shell morphology and anatomy of Pisidium kawamurai hukuiense Mori, 1938 and P. japonicum Pilsbry and Hirase,1908 were studied. The diagnostic characters of P. k. hukuiense are the roundly ovate outline, distinct and regular striae, evenly arranged mantle muscle bundle scars separated from the pallial line and the nephridium with an elongated dorsal lobe. P. japonicum is characterized by its subglobose shell, the pseudocallus at the anterior end of P III and the small outer demibranch.
The bivalve mollusk Halicardia akitaensis Ogasawara & Takayasu is present in the Lower Miocene Mitsugano Tuffaceous Shale and Sandstone Member of the Oi Formation, Ichishi Group, at Iedokoro, Misato-cho, Tsu City, Mie Prefecture, central Japan. Halicardia inhabits the bathyal zone, and the specimen, with articulated valves, was evidently deposited at its living site or in deeper water. Associated taxa include bathyal benthic mollusks that were abundant during the Early Miocene.
Diverse and abundant populations of sacoglossan opisthobranchs inhabit Japanese rocky shores. The species of sacoglossans that feed on the green macroalgae Codium spp. were investigated in and around Sagami Bay on the Pacific coast of Honshu, Japan. On the Miura and Izu Peninsulas, two sacoglossan species were particularly common: Elysia trisinuata Baba, 1949 and E. setoensis Hamatani, 1968. Phenology and algal host use of these species are described. Elysia trisinuata grew substantially larger than sympatric sacoglossan species on Codium with maximum weight of 821 mg. Small E. trisinuata recruited to algal hosts primarily in summer. Some grew and spawned by autumn whereas others apparently over-wintered and spawned in spring. This sacoglossan associated with and fed on 6 of 8 Codium spp. investigated in this study and 4 additional Codium species in other studies. The congener E. setoensis was substantially smaller (max. 64 mg) than E. trisinuata and was frequent on C. fragile and C. intricatum in summer as well as present on 4 other genera of coenocytic green algae (Bryopsis, Caulerpa, Caulerpella, and Cladophoropsis). Although peak abundance of E. setoensis was in spring and summer, this species also persisted through the winter. Five additional species of sacoglossans associated with Japanese Codium spp. are briefly summarized.
The population dynamics of Batillaria zonalis, an opportunistic feeder, were examined in the Yone intertidal flat on Okinawa Island, Japan, from January 2001 to December 2002. Batillaria zonalis was the most dominant species, although other gastropods were present (B. flectosiphonata and Cerithidea cingulata). The highest density and biomass of B. zonalis were observed during the winter. Batillaria zonalis reached 21.0 mm in its first year of life and a maximum length of 31.5 mm in 9 years, as estimated from von Bertalanffy growth curve parameters. Batillaria zonalis recruited at least four times during the two years, but younger individuals (shell length < 21 mm) were at very low densities compared with a previous study. The small number of recruits and the low density of younger specimens may not sustain the B. zonalis population. Its food sources, the macroalga Ulva pertusa and chlorophyll-a in seawater and sediment, peaked at different times of the year. The season of highest U. pertusa coverage seemed to support the highest B. zonalis biomass. The B. zonalis population declined following a decrease in U. pertusa. The surviving B. zonalis probably lived off a chlorophyll-a in the sediment and seawater; therefore, the population is probably maintained by opportunistic feeding.
The eulimid gastropod Hypermastus tokunagai was found to be parasitic on the irregular sea urchin Scaphechinus mirabilis. An ecological study of this parasitic snail was conducted monthly from May 2005 to May 2006 in the western part of the Seto Inland Sea. The parasite rather loosely attached itself to the integument of the host by its proboscis, but no hole was observed in the scar formed at the attachment position. Free-living H. tokunagai were also found in the bottom sediment in the survey area. Thus, the mode of parasitism of H. tokunagai is assumed to be relatively independent and association with its host temporary. There was no relationship between the degree of infestation and the size of the host. Most parasites attached themselves to the oral side of the host, with a significant preference for the peripheral portion. The prevalence and the mean abundance increased in the spring and autumn, and decreased in summer and winter.
To evaluate shell thickness and factors affecting it, weights and heights of 2097 Pomacea canaliculata shells were measured. Specimens were obtained from paddy fields and adjacent canals in two areas in Kawasoe-machi, Saga Prefecture, Japan (33°11'N, 130°19'E), in 2004. Logarithm-transformed shell weights and heights revealed a good regression line, and the deviation of actual weight from expected weight of each shell was regarded as a representative of overall shell thickness (the shell-thickness index). Values of the index were larger in shells collected from canals than in those from paddy fields. Overall, shells appeared to be thinner in June and July than in August and November, irrespective of habitats, presumably due to rapid growth of the snail in early summer.