TITLE:
Molecular Phylogenetic Analysis of Chemosymbiotic Solemyidae and Thyasiridae
AUTHORS:
Youki Fukasawa, Hiroto Matsumoto, Saori Beppu, Yoshihiro Fujiwara, Masaru Kawato, Jun-Ichi Miyazaki
KEYWORDS:
Whale Bone, Deep Sea, Nuclear DNA, Mitochondrial DNA, Stepping Stone Hypothesis
JOURNAL NAME:
Open Journal of Marine Science,
Vol.7 No.1,
January
18,
2017
ABSTRACT: 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.