頼末 武史

Hybridization of monoterpene and furan structural scaffolds increased antifouling activity.

Geographical traceability of marine bivalves is becoming increasingly important to assure their quality and to defend the interest of consumers and producers. This study verifies the neodymium isotopic ratio (143Nd/144Nd) in Ruditapes philippinarum shells as a tracer of the geographic origin, based on the geochemical aspect that 143Nd/144Nd of their habitats strongly depends on the geology of its catchment areas. The 143Nd/144Nd ratios of clam shells from the Japanese and Chinese coastal areas displayed a heterogeneous pattern from local to international scales, reflecting the geological age of the catchment area. The blind test suggested that a part of Manila clam was sold with mislabeling in the Japanese market, demonstrating the high potential of 143Nd/144Nd to unmask the fraud labeling in a food market. Our findings emphasize the potential of 143Nd/144Nd as a tracer for the geographical origin of marine bivalves, and also as a strong deterrent against mislabeling.

Marine cave habitats in the Ryukyu Islands, Indo-West Pacific, are located at the northern edge of the distribution of many cave-dwelling species. At distribution margins, gene flow is often more restricted than that among core populations due to the smaller effective population size. Here, we used high-throughput sequencing technology to investigate the gene flow pattern among three sampling sites of a marine cave-dwelling species at the margin of its distribution range. We collected individuals of the barbouriid shrimp <italic>Parhippolyte misticia</italic> from three marine caves in the Ryukyu Islands and performed population genetic analyses by means of multiplexed inter-simple sequence repeat genotyping by sequencing. Based on 62 single-nucleotide polymorphism markers, no clear population structure or directional gene flow pattern was found among the three sites. These results were unexpected because previous studies of other stygobitic shrimps in this region did find significant population genetic structures and northward directional gene flow patterns <italic>.</italic> Together, these inconsistent findings imply that marine cave-dwelling species in the region have different mechanisms of larval dispersal. Future studies on larval ecology and the biotic and abiotic factors influencing gene flow patterns are needed to clarify the mechanisms underlying the population dynamics of marine cave-dwelling species.

Birgus latro (coconut crab) is an edible crustacean that has experienced serious overharvesting throughout its whole habitat range; however, the negative effects of overharvesting on the genetic diversity within B. latro populations have not been elucidated. Here, we report sex ratio, body size, and genetic diversity in populations of B. latro in the Ryukyu Islands where large-male-biased overharvesting of B. latro has continued. In 2 of the study populations, the sex ratio was significantly skewed toward females, and in all of the study populations large males were rare, which we attributed to sex- and size-biased overharvesting. We found no differences in genetic diversity between small and large individuals, suggesting that genetic diversity, even among the large (i.e., old) individuals, may have had already been negatively affected by overharvesting. Continued monitoring of sex ratio, body size and genetic diversity are needed for effective management of the study populations.

Intertidal limpets are important grazers along rocky coastlines worldwide that not only control algae but also influence invertebrates such as common barnacles. For instance, grazing limpets ingest settling barnacle cyprid larvae (hereafter cyprids) and push cyprids and barnacle recruits off the substrate. Such limpet disturbance effects (LDEs) can limit barnacle recruitment, a key demographic variable affecting barnacle population establishment and persistence. In this study, we examined limpet (<italic>Lottia cassis</italic>) disturbance to barnacle (<italic>Chthamalus dalli</italic>, <italic>Balanus glandula</italic>) recruitment on the Pacific coast of Hokkaido, Japan, as information on limpet-barnacle interactions from this region is missing. We investigated, for the first time, whether barnacle size and recruitment intensity influence LDEs on barnacle recruitment. Small barnacles may be less susceptible to LDEs than larger barnacles, because small size may reduce the propbability of limpet disturbance. Moreover, recruitment intensity can influence LDEs, as high recruitment can compensate for LDEs on barnacle recruitment density. In Hokkaido, <italic>C. dalli</italic> cyprids are smaller than <italic>B. glandula</italic> cyprids, and <italic>C. dalli</italic> recruitment is higher than <italic>B. glandula</italic> recruitment. Thus, we hypothesized that LDEs on <italic>C. dalli</italic> recruitment would be weaker than those on <italic>B. glandula</italic> recruitment. To test our hypothesis, we conducted a field experiment during which we manipulated limpet presence/absence on the interior surfaces of ring-shaped cages. After four weeks, we measured barnacle recruitment and recruit size on the interior surfaces of the cages and found negative LDEs on <italic>C. dalli</italic> and <italic>B. glandula</italic> recruitment and recruit size. As hypothesized, the LDEs on <italic>C. dalli</italic> recruitment were weaker than the LDEs on <italic>B. glandula</italic> recruitment. Additionally,<italic> C. dalli</italic> recruits were smaller than <italic>B. glandula</italic> recruits. However, the LDEs on <italic>C. dalli</italic> recruit size were as strong as the LDEs on <italic>B. glandula</italic> recruit size, indicating that the smaller<italic> C. dalli</italic> recruits are not less susceptible to LDEs than <italic>B. glandula</italic> recruits. Since <italic>C. dalli</italic> recruitment was higher than <italic>B. glandula</italic> recruitment, we propose that the higher <italic>C. dalli</italic> recruitment compensated for the LDEs on <italic>C. dalli</italic> recruitment. Our findings indicate that the detected differences in LDEs on barnacle recruitment are related to barnacle recruitment intensity but not recruit size.

Symposium mini review

Many coastal barnacles are introduced to non-native regions. However, data are lacking on cryptic invasion, which is defined as an invasion that remains unrecognised because the invader is mistaken for a native or previously introduced species or clade. In this work, cryptic invasions of an intertidal barnacle, Semibalanus cariosus, between Japan and the north-eastern Pacific were evaluated based on population genetic analyses. A significant genetic differentiation was found between the Japanese and north-eastern Pacific populations, suggesting a limited introduction of non-native genotypes between these regions. Haplotype frequencies did not differ significantly between the past (museum samples collected in 1971 from Hokkaido, Japan) and present Japanese populations, implying the rare occurrence of human-mediated migration from the north-eastern Pacific to Japan. Migrate-n analysis revealed a low level of directional gene flow in S. cariosus from the north-eastern Pacific to Japan, possibly by natural stepping-stone dispersal via directional water currents or human-mediated transport.

Barnacle cypris larvae show high morphological variation in the organs used in search of and attaching to a substratum. This variation may represent adaptation to the habitat of the species. Here, we studied SEM level morphologies of cypris antennular sensory and attachment organs in a deep-sea vent endemic species (Neoverruca sp.) and a vent/seep inhabiting species (Ashinkailepas seepiophila). We compare them with three species from other environments. The antennular morphologies of Neoverruca sp. and A. seepiophila were similar, which is consistent with recent molecular studies showing a close relationship of the two species. The setation pattern of the antennules was very conservative among species from various environments. In contrast, striking differences were observed in the structure of the attachment organ (the third antennular segment). Neoverruca sp. and A. seepiophila had no velum or a skirt surrounding the attachment disc on the third segment, while other cirripede cyprids almost always have either of these structures. In addition, both cyprids of A. seepiophila and Neoverruca sp. had the attachment disc angled toward the substratum, whereas it faces distally in cyprids from hard bottom inhabiting barnacles. We suggest that both velum/skirt and the angle of the attachment disc play an important role, when the antennules are contacting the substratum during surface exploration. Differences in attachment organ structures may be highly adaptive, enabling cirripede species to enter new habitats during evolution. J. Morphol. 277:594-602, 2016. (c) 2016 Wiley Periodicals, Inc.

Snails of the genus Batillaria are common on most muddy tidal flats throughout Japan. To conserve tidal flat ecosystems, it is essential to understand the ecology of the Batillaria snails. A previous mitochondrial (mt) cytochrome c oxidase subunit I (COI) gene sequence analysis indicated that two Batillaria species, B. flectosiphonata and B. multiformis, occur together on the tidal flats on Amami-Oshima, Japan. However, it is difficult to distinguish them by their morphological traits. In this study, a simple multiplex PCR (mPCR)-based method was developed to identify the two species without the need for DNA sequencing. The method allows the discrimination of species by the electrophoretic detection of species-specific DNA fragments of the COI gene amplified by mPCR. This method will enhance the ecological study of these Batillaria snails on Amami-Oshima.

Deep-sea hydrothermal vents and cold seeps are scattered and limited habitats, and species that are confined to these benthic habitats often have a planktonic larval stage in their life history to maintain dispersal and gene flow among discrete populations. We have reared the larvae of Ashinkailepas seepiophila, inhabiting inactive vents and active cold seeps, through their entire larval development under atmospheric pressure. Using two temperatures (4 degrees C, 10 degrees C) we examined whether larval development resembles other vent species in being affected by thermal stimulation. Under laboratory conditions, A. seepiophila completed larval development in 65 days at 4 degrees C This is considerably shorter than the 100 days previously reported to be required at the same temperature by Neoverruca sp., a species confined to inhabiting active vents. Also in contrast to Neoverruca sp., A. seepiophila did not drastically shorten the developmental period from nauplius VI to cyprid when exposed to temperature of 10 degrees C. We conclude that there is no need for late naupliar stages of A. seepiophila to develop into cyprids more quickly at elevated temperatures because this species does not inhabit active vents. The difference in response to water temperature during larval development may contribute to the separated distribution of the two species at active vents (Neoverruca sp.) and inactive vents and cold seep (A. seepiophila) environments. (C) 2012 Elsevier Ltd. All rights reserved.

To investigate and compare the trophic structures of hydrothermal vent communities at different depths, the carbon and nitrogen stable isotope ratios of dominant species were analyzed in the communities at Myojin Knoll (1,220-1,360 m) in the Izu-Ogasawara Arc and the Nikko Seamount (380-550 m) in the North Mariana Arc. At the Myojin knoll, a barnacle, Ashinkailepas seepiophila had high δ15N value, which suggested to be derived from photosynthetic products. Similarly, at Nikko Seamount, a polynoid polychaete, Gandulfus yunohana, a xanthid crab, Alvinocaaris sp., and Symphurus thermophilus had high δ15N values. These animals, too, are suggested to consume photosynthetic products. The range of δ13C values at Myojin Knoll was wider than that at Nikko Seamount. The difference between the ranges of these values suggest that different chemical environments between the two vent sites influence the components and distribution of chemoautotrophic bacteria found at each site, leading to different faunal compositions. © 2012, The Plankton Society of Japan, The Japanese Association of Benthology. All rights reserved.

Gregarious settlement is essential for reproduction and survival of many barnacles. A glycoprotein, settlement-inducing protein complex (SIPC) has been recognized as a signal for settlement and it is expressed in both conspecific adults and larvae. Although the settlement-inducing activities of SIPC are species-specific, the molecular-based mechanism by which larvae distinguish conspecific SIPC from the SIPC of other species is still unknown. Here, the complete primary structure of the SIPC of Megabalanus coccopoma, as well as the partial structure of the SIPCs of Balanus improvisus, Megabalanus rosa, and Elminius modestus are reported. These SIPCs contain highly variable regions that possibly modulate the affinity for the receptor, resulting in the species specificity of SIPC. In addition, the distribution patterns of potential N-glycosylation sites were seen to be different among the various species. Differences in such post-translational modifications may contribute to the species specificity of SIPC.