title: Extremely low genetic variability within and among locations of the greenfish holothurianStichopus chloronotusBrandt, 1835 in Okinawa, Japan.
abstract: The greenfish sea cucumberStichopus chloronotusis an economically and ecologically important sea cucumber species throughout its range. This species is widely distributed, inhabiting coral reefs of the Indo-Pacific Ocean. Our study evaluated population genetic structure and levels of genetic diversity in southern Japan. A total of 180 individuals were collected from eight locations from Okinawa and Okinoerabu Islands and sequenced using mitochondrial 16S ribosomal DNA (16S) and nuclear histone H3 (H3) gene. Only three 16S haplotypes were detected (518 bp) with haplotype diversity ranging from 0 to 0.56 and nucleotide diversity from 0 to 0.1%. H3 showed no variation among the studied locations. It is plausible that such results could be due to a shift to asexual reproduction.Additionally, the presence of the species on the east coast of Okinawa could only be detected in one location and all individuals consisted of a single haplotype. Genetic differences between the east and west coasts of Okinawa have been noticed in other coral reef organisms, and attributed to either ecological or biogeographical historical differences between the coasts due to differing levels of isolation during Pleistocene ice ages. Results from the present study should inform management and conservation policies ofS. chloronotusin southern Japan.
authors.affiliation: Molecular Invertebrate Systematics and Ecology Laboratory, Graduate School of Engineering and Science, University of the Ryukyus, Nishihara, Okinawa, Japan; National Institute of Oceanography and Fisheries, Alexandria, Egypt; Microbiology and Biochemistry of Secondary Metabolites Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, Japan.
authors.forename: Taha
authors.initials: T
authors.lastname: Soliman
authors.affiliation: Molecular Invertebrate Systematics and Ecology Laboratory, Graduate School of Engineering and Science, University of the Ryukyus , Nishihara , Okinawa , Japan.
authors.forename: Okuto
authors.initials: O
authors.lastname: Takama
authors.affiliation: Molecular Invertebrate Systematics and Ecology Laboratory, Graduate School of Engineering and Science, University of the Ryukyus, Nishihara, Okinawa, Japan; Section of Ichthyology, California Academy of Sciences, San Francisco, CA, USA; Department of Biochemistry, Genetics and Immunology, Campus Universitario, University of Vigo, Vigo, Spain.
authors.forename: Iria
authors.initials: I
authors.lastname: Fernandez-Silva
authors.affiliation: Molecular Invertebrate Systematics and Ecology Laboratory, Graduate School of Engineering and Science, University of the Ryukyus, Nishihara, Okinawa, Japan; Tropical Biosphere Research Center, University of the Ryukyus, Nishihara, Okinawa, Japan.
authors.forename: James D
authors.initials: JD
authors.lastname: Reimer
keywords: 16S ribosomal DNA; Okinawa Island; Sea cucumber; Stichopus chloronotus; mtDNA