New distribution record of deep-sea mussel, Bathymodiolus aduloides (Mollusca: Bivalvia: Mytilidae) from a hydrothermal vent, Myojinsho

From the deep-sea hydrothermal vents and cold seeps ecosystems, more than 600 species containing many endemic species have been discovered. The deep-sea mussels of the genus Bathymodiolus are dominant species at deep-sea hydrothermal vents and cold seeps throughout the world. They are known to rely on the nutrients produced by the chemosynthetic symbiont in their gills. In 2009, we found a colony of bathymodiolin mussels at a hydrothermal vent of Myojinsho (Myojin Reef), which is a hardly investigated area. Myojinsho lies in the northern segment of the Izu-Ogasawara (Bonin) Arc and had been volcanically active until recently. We collected specimens from the colony using a remotely operated vehicle. We identified them as Bathymodiolus aduloides by morphological observation and phylogenetic analyses using mitochondrial DNA sequencing. We could not find any other species of mussels during the dive. This result is interesting because this species has not been discovered from hydrothermal vents in this region; the dominant species in this region, including the neighbouring Myojin Knoll Caldera, is B. septemdierum

Evolutionary History of the GABA Transporter (GAT) Group Revealed by Marine Invertebrate GAT-1

<div><p>The GABA transporter (GAT) group is one of the major subgroups in the solute career 6 (SLC6) family of transmembrane proteins. The GAT group, which has been well studied in mammals, has 6 known members, i.e., a taurine transporter (TAUT), four GABA transporters (GAT-1, -2, -3, - 4), and a creatine transporter (CT1), which have important roles in maintaining physiological homeostasis. However, the GAT group has not been extensively investigated in invertebrates; only TAUT has been reported in marine invertebrates such as bivalves and krills, and GAT-1 has been reported in several insect species and nematodes. Thus, it is unknown how transporters in the GAT group arose during the course of animal evolution. In this study, we cloned GAT-1 cDNAs from the deep-sea mussel, <i>Bathymodiolus septemdierum</i>, and the Antarctic krill, <i>Euphausia superba</i>, whose TAUT cDNA has already been cloned. To understand the evolutionary history of the GAT group, we conducted phylogenetic and synteny analyses on the GAT group transporters of vertebrates and invertebrates. Our findings suggest that transporters of the GAT group evolved through the following processes. First, GAT-1 and CT1 arose by tandem duplication of an ancestral transporter gene before the divergence of Deuterostomia and Protostomia; next, the TAUT gene arose and GAT-3 was formed by the tandem duplication of the TAUT gene; and finally, GAT-2 and GAT-4 evolved from a GAT-3 gene by chromosomal duplication in the ancestral vertebrates. Based on synteny and phylogenetic evidence, the present naming of the GAT group members does not accurately reflect the evolutionary relationships. </p> </div

Comparison of amino acid sequences of marine invertebrate and mammalian GAT-1.

<p>Human GAT-1 (HsGAT-1), ratGAT-1 (RnGAT-1), <i>B. septemdierum</i> GAT-1 (BsGAT1), and <i>E. superba</i> GAT-1 (EsGAT1) were compared. Identical amino acids are indicated by asterisks; conservative substitutions are indicated by a single dot; putative transmembrane domains (I-XII) are shaded; red boxes indicate position of amino acids known to be important for the functions of RnGAT-1.</p

Localization of GAT group member genes on chromosomes of vertebrates.

<p>(A) human, (B) green anole, (C) medaka. Ch, chromosome; LG, linkage group.</p

Molecular phylogenetic tree of the GAT group members of vertebrates and invertebrates constructed by Bayesian method.

<p>The posterior probabilities are shown on the top left part of a branch. The scale bar represents a phylogenetic distance of 0.1 substitutions per site. <i>B. septemdierum</i> GAT-1 (BsGAT1) and <i>E. superba</i> GAT-1 (EsGAT1) are shown in red and their TAUTs are shown in blue. </p

Proposed molecular evolutionary history of GAT group member genes.

<p>* Since which of GAT-2 and GAT-4 was created first is unclear, their ancestor is shown as GAT-2/4. </p

二枚貝類における２つの二価金属イオン輸送体の探索と機能解析

http://www.godac.jamstec.go.jp/darwin/cruise/natsushima/nt14-06/