Genetic lineage of the Amami islanders inferred from classical genetic markers

The peopling of mainland Japan and Okinawa has been gradually unveiled in the recent years, but previous anthropological studies dealing people in the Amami islands, located between mainland Japan and Okinawa, were less informative because of the lack of genetic data. In this study, we collected DNAs from 104 subjects in two of the Amami islands, Amami-Oshima island and Kikai island, and analyzed the D-loop region of mtDNA, four Y-STRs and four autosomal nonsynonymous SNPs to clarify the genetic structure of the Amami islanders comparing with peoples in Okinawa, mainland Japan and other regions in East Asia. We found that the Amami islanders showed genetically intermediate position between mainland Japan and Okinawa in mtDNA and Y-STR. However, the frequencies of several autosomal SNPs in the Amami islanders indicated significant difference from mainland Japanese, and it may be due to the gene flow from Okinawa but not natural selection. Furthermore, extremely high or low frequencies of several alleles implied the existence of founder effect in Kikai islanders. It should be noted that there is room for the interpretation of the results because of the small sample size and number of alleles in the present study, and geographically broad and detailed samplings and genome-wide analyses are awaited.

Redescription of a poorly known upogebiid mud shrimp Gebiacantha acanthochela (Sakai, 1967) and description of a new species of the genus from the Ryukyu Islands, Japan (Decapoda: Gebiidea)

Two species of the upogebiida mud shrimp genus Gebiacantha Ngoc-Ho, 1989, currently represented by 19 described species, are reported from the Ryukyu Islands, Japan. The first, G. acanthochela (Sakai, 1967), is redescribed in detail based on two female specimens from Amami Islands the second discovered since the original description, enabling better assessment of its diagnostic characters. The second, G. fortispinata n. sp., is described on the basis of a single female holotype from Okinawa Island. It appears closest to G. multispinosa Ngoc-Ho, 1994, known with certainty only from New Caledonia, but the proportionally narrower telson with a more deeply notched posterior margin and the distally unarmed pereopod 3 merus distinguish the new species from G. multispinosa. Three species of Gebiacantha, including G. sagamiensis Komai, 2017, are now known from Japanese waters.