Author(s)

Youki Fukasawa¹, Hiroto Matsumoto², Saori Beppu², Yoshihiro Fujiwara³, Masaru Kawato³, Jun-Ichi Miyazaki^2*

¹Graduate School of Medical and Engineering Science Department of Education, University of Yamanashi, Kofu, Japan.
²Faculty of Education and Human Sciences, University of Yamanashi, Kofu, Japan.
³Department of Marine Biodiversity Research, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan.

In order to invade and adapt to deep-sea environments, shallow-water organisms have to acquire tolerance to high hydrostatic pressure, low water temperature, toxic methane and hydrogen sulfide, and feeding strategies not relying on photosynthetic products. Our previous study showed that the “evolutionary stepping stone hypothe-sis”, which assumes that organic falls can act as stepping-stones to connect shallow sea with deep sea, was supported in Mytilidae. However, it is not known whether other bivalves constituting chemosynthetic communities experienced the same evolutionary process or different processes from mytilid mussels. Therefore, here, we performed phylogenetic analyses by sequencing the nuclear 18S rRNA and mitochondrial COI genes of solemyid and thyasirid bivalves. In Solemyidae, the two genera Solemya and Acharax formed each clade, the latter of which was divided into three subgroups. The Solemya clade and one of the Acharax subgroups diverged in the order of shallow-sea residents, whale-bone residents, and deep-sea vent/seep residents, which supported the “evolutionary stepping stone hypothesis”. Furthermore, in Thyasiridae, the two genera Thyasira and Maorithyas formed a paraphyletic group and the other genera, Adontorhina, Axinopsis, Axinulus, Leptaxinus, and Mendicula, formed a clade. The “evolu-tionary stepping stone hypothesis” was not seemingly supported in the other lineages of Solemyidae and Thyasiridae.

Whale Bone, Deep Sea, Nuclear DNA, Mitochondrial DNA, Stepping Stone Hypothesis

Fukasawa, Y. , Matsumoto, H. , Beppu, S. , Fujiwara, Y. , Kawato, M. and Miyazaki, J. (2017) Molecular Phylogenetic Analysis of Chemosymbiotic Solemyidae and Thyasiridae. Open Journal of Marine Science, 7, 124-141. doi: 10.4236/ojms.2017.71010.