琉球列島サンゴ礁域に生息するアワモチ科(軟体動物:腹側綱)の多様性、分布および食用利用に関する研究

Abstract

Family Onchiiidae consists of air-breathing sea slug that lack internal or external shell. They are mostly found in intertidal areas across globe, except in the polar regions, and inhabit marine habitats. Although they are known to be commonly distributed in tropical to temperate of Indo-West Pacific region, information about the diversity of family Onchidiidae in the Ryukyu Islands is greatly lacking. Particularly, genus Peronia serves as an important traditional food source on many islands of the Ryukyus, but due to extremely similar gross morphology among the species, frequent misidentification of this family occurred in guidebooks and literatures. Accurate species identification requires detailed taxonomic analyses that incorporate molecular and morphological datasets, and literature reviews. Thus, in this thesis, I focused on three genera of family Onchidiidae; Peronia, Wallaconchis and Onchidella inhabit intertidal coral reef environments, and aimed to accomplish three goals. Firstly, I investigated the species diversity and distribution ranges of three genera across 40 intertidal areas in 11 islands of the Ryukyu Islands, with Chapter 1 focused specifically on genus Peronia and Chapter 2 adressed genera Wallaconchis and Onchidella. As a results of mitochondrial DNA barcoding using COI and 16S regions, the Ryukyu Islands harbor at least eight species from three genera; four species of Peronia (P. verruculata, P. peronii, P. okinawensis, and P. setoensis), three species of Wallaconchis (W. ater, W. nangkauriensis, and Wallaconchis sp.) and one species of Onchidella (Onchidella sp.). Species of Peronia distributed Iriomote-jima to Yakushima islands, and Wallaconchis and Onchidella are distributed in Okinawa-jima to Kikai-jima. Alive photographs of each species are also provided as potential identification tools, as well as to understand the colour variations observed within the species. Secondly, to enhance the molecular datasets of family Onchidiidae in public repositories, I aimed to provide the complete mitochondrial genomes of genus Peronia. The characteristics of mitogenomes of four species of Peronia are described in Chapter 4, with the first records of P. okinawensis and P. setoensis. It revealed that all species shared the same gene orientation and arrangement as previously described mitogenomes in family Onchidiidae. Thirdly, I aimed to explore the traditional Peronia fishery across eight islands through in-person interview with locals in Chapter 5. The Peronia fishery was observed from eight islands, either as active practice or one that has diminished over time. While locals recognized Peronia as a food source by locals, but familiarity with them varied slightly across eight islands. Overall, this thesis has revealed that currently the Ryukyu Islands hold the highest species diversity of genus Peronia, with four species coinhabit the same intertidal areas, as well as five species from three genera sympatrically existed. Although species of Onchidiidae can be currently considered as “common” in the Ryukyu Islands, more studies are needed to investigate the relationships between their diversity and the impacts of artificial disturbances, coastal developments, and overexploitations in intertidal areas to protect this unique biodiversity.博士（理学）http://purl.org/coar/resource_type/c_db06琉球大学University of the Ryukyu