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The genetic structure of the vestimentiferan Lamellibrachia satsuma (Annelida: Siboglinidae) distributed in Kagoshima Bay, southwestern Japan, and the Nikko and Daikoku seamounts on the northern Mariana Arc, was analyzed using 14 newly developed microsatellite markers. We detected large genetic differences between the L. satsuma distributed in Japanese and Mariana waters, whereas no significant divergence was detected between local populations inhabiting the calderas of the two Mariana seamounts, which are separated by a distance of approximately 270 km. STRUCTURE analysis revealed that two genetically distinct clusters are dominant and no genetic differentiation was detected between sampling years or sites in Kagoshima Bay. We speculated that the Kagoshima Bay population is derived from individuals that have immigrated relatively recently from two undiscovered habitats in waters outside of the bay. [ABSTRACT FROM AUTHOR]

The reproductive season and life span of the common estuarine polychaete Simplisetia erythraeensis (Annelida: Nereididae) was investigated by monthly sampling during the years 2015 and 2016 in two tidal flats at two different regions in southern Japan: Shigetomi in Kagoshima Bay, Kyusyu Island, a warm-temperate region and Ichi on Amami-Oshima Island, Ryukyu Islands, a maritime subtropical region. At both sites, one or two cohorts were distinguished simultaneously using monthly body-width histograms. Recruitment of new cohorts occurred from August in Kagoshima Bay and from July on Amami-Oshima Island. Ovigerous females were observed from March to August in the former area and from April to July in the latter area, with the highest female maturity rate (number of females with oocytes/total number of adults larger than the smallest mature size) in July in both areas. The maximum value of the mean oocyte size of each female increased with increasing female maturity rates. The density of each cohort decreased from May onward because of the death of adults after reproduction, which resulted in the complete disappearance of the cohort in early October. Our results showed that the life span of S. erythraeensis was one year, and the reproductive period occurred in summer. [ABSTRACT FROM AUTHOR]

Lingula species are brachiopods inhabiting the tidal flats. In Japan, they are threatened by the marine pollution and decreasing habitat. Although these brachiopods are endangered in Japan, little is known about their life history. The aim of this study was to examine the life history characteristics of Lingula anatina after settlement in Kasari Bay, Amami-Oshima Island, Kagoshima, Japan, by measuring the gonad index and seasonal changes in size distribution. The results revealed that the breeding season of this species is from summer to early autumn, which is longer than that of other populations in Japan. Their settlement starts in winter after the planktonic stage, and they reach maturity after two or three years. Their longevity is more than four years and they breed every year. Lingula species are under taxonomic revision; therefore, for convenience, we named the species in Amami-Oshima as Lingula anatina. [ABSTRACT FROM AUTHOR]

The present study investigated the distribution of Batillaria multiformis and B. attramentaria in the tidal flats of Southern Kyushu. These two species are the dominant inhabitants of tidal flats and play an important role in conserving the environmental condition of the coastal area. Since it is difficult to distinguish between the two species based on shell morphology, the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) technique was used for identification. Among the 55 tidal flats surveyed, Batillaria species were found in 32, mainly along the coasts of Kagoshima Bay and East China Sea. Furthermore, these species were not observed in certain tidal flats, although their presence in these tidal flats was confirmed from 1999 to 2003. The reason for their absence or decline has been discussed here. Batillaria multiformis was distributed along the neighboring tidal flats of inner Kagoshima Bay and around Nagashima Island, whereas B. attramentaria was isolated along a few scattered tidal flats facing to the Pacific Ocean or East China Sea. The difference in the distribution of two species might be attributed to their developmental system'B. multiformis and B. attramentaria employ planktonic and direct developmental systems, respectively. [ABSTRACT FROM AUTHOR]