Molecular characterization of the zoanthid genus Isaurus (Anthozoa: Hexacorallia) and associated zooxanthellae (Symbiodinium spp.) from Japan
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The zoanthid genus Isaurus (Anthozoa: Hexacorallia) is known from both the Indo-Pacific and Atlantic Oceans, but phylogenetic studies examining Isaurus using molecular markers have not yet been conducted. Here, two genes of markers [mitochondrial cytochrome oxidase subunit I (COI) and mitochondrial 16S ribosomal DNA (mt 16S rDNA)] from Isaurus specimens collected from southern Japan (n = 19) and western Australia (n = 3) were sequenced in order to investigate the molecular phylogenetic position of Isaurus within the order Zoantharia and the family Zoanthidae. Additionally, obtained sequences and morphological data (polyp size, mesentery numbers, mesogleal thickness) were utilized to examine Isaurus species diversity and morphological variation. By comparing our obtained sequences with the few previously acquired sequences of genera Isaurus as well as with Zoanthus, Acrozoanthus (both family Zoanthidae), and Palythoa spp. (family Spenophidae) sequences, the phylogenetic position of Isaurus as sister to Zoanthus within the Family Zoanthidae was suggested. Based on genetic data, Isaurus is most closely related to the genus Zoanthus. Despite considerable morphological variation (in particular, polyp length, mesentery numbers, external coloration) between collected Isaurus specimens, all specimens examined are apparently conspecific or very closely related based on molecular data and observed morphological variation within colonies. Additionally, obtained internal transcribed spacer of ribosomal DNA (ITS-rDNA) sequences from symbiotic zooxanthellae (Symbiodinium spp.) from all Isaurus specimens were shown to be subclade C1-related Symbiodinium.
JDR would like to thank Koki Tanaka (BIK), Mai Miyamoto and Miho Watanabe (both Tokyo University of Marine Science and Technology), Dr. Kensuke Yanagi (Coastal Branch of Natural History Museum and Institute, Chiba), Hiroko Haraguchi (Kochi University), Yuichi Nagata and Mika Reimer for assistance in sampling. As well, Kazutoshi Nishimoto and Atsushi Nishimoto (both Tatsukushi Port) helped with guidance during zoanthid surveys. Dr. Jane Fromont and Dr. Mark Salotti (WAM) kindly loaned Z. praelongus and Isaurus samples, with an introduction from Max Rees (Australian Institute of Marine Science). Australian samples were collected by WAM as part of a SRFME funded project on the Central West Coast of Australia. Additionally, Dr. Hiroomi Uchida (Kushimoto Marine Park, Wakayama) and Frederic Sinniger (University of Geneva) kindly loaned us other samples or information utilized in this study. At JAMSTEC, Masaru Kawato and Hirokazu Kuwahara helped with sequencing. Dr. Kiyotaka Takishita (JAMSTEC) and comments from three anonymous reviewers greatly improved the manuscript. All experiments described within comply with the current laws of Japan.
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