Research Article

Marine Biology

, Volume 153, Issue 3, pp 351-363

First online:

Molecular characterization of the zoanthid genus Isaurus (Anthozoa: Hexacorallia) and associated zooxanthellae (Symbiodinium spp.) from Japan

  • James Davis ReimerAffiliated withResearch Program for Marine Biology and Ecology, Extremobiosphere Research Center, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)Biological Institute on KuroshioDepartment of Marine Science, Biology and Chemistry, Faculty of Science, University of the Ryukyus Email author 
  • , Shusuke OnoAffiliated withMiyakonojo Higashi High School
  • , Junzo TsukaharaAffiliated withDepartment of Developmental Biology, Faculty of Science, Kagoshima University
  • , Fumihito IwaseAffiliated withBiological Institute on Kuroshio

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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.