Study on the Origin of Deep-sea Hydrothermal Vent Communities at the Lau Back-Arc Basin, Southwest Pacific

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This is report on the morphological, ecological, biogeographic and molecular biological studies for vent communities collected at our expedition to the deep-sea hydrothermal vents at the Lau and Havre Back-arc Basins, Southwest Pacific from September 23 to November 10,2004 using Japanese submersible "Shinkai 6500" and her mother ship "Yokosuka." The main target of this research project is to clarify origin and evolution of the deep-sea hydrothermal vent and cold seep communities of the Southwest Pacific.The Lau and Havre Back-arc Basins, Southwest Pacific hold communities of high biological diversity in comparison with other such vent and seep communities in the world based on our research of principal component in the deep-sea hydrothermal vent and seep communities such as bivalves, gastropods, crustaceans (including crabs, shrimps and barnacles), worms, tube-worms, etc. Particularly, barnacles in crustacean shown the highest diversity in the known deep-sea vent and seep of the world. … More We could found all four suborders, Scalpellomorpha, Brachylepadomorpha, Verrucomorpha, and Balanomorpha from the Lau Basin. And the peripheral areas of the Lau Basin such as North Fiji and Manus Basins show the second high biological diversity hold three suborders except Brachylepadomorpha.The morphological examination of barnacles collected from the Lau and Havre basins shows that scalpellomrphan barnacle Ashikailepas has the most primitive morphological characteristics and also the widest distribution at the West Pacific.The molecular biology of some principal vent animals collected from the Lau and Havre basins shown primitive phylogenetic position in comparison with the group of the East Pacific, West Pacific (Northwest to Southwest) and Indian Oceans. Ashinkailepas in comparison with two Japanese and one Havre populations population shows the most primitive Scalpellomorph in the molecular phylogeny. Therefore, the origin of the known vent and seep communities seems to be Southwest Pacific. Less