Morphological and Genetic Diversity ofBriareum(Anthozoa: Octocorallia) from the Ryukyu Archipelago, Japan

Abstract

The primary problem hindering the study of octocorals is the disordered situation regarding their taxonomy, chiefly caused by insufficient knowledge of valid morphological taxonomic characters. Briareum is an octocoral genus found in the Atlantic and Pacific in shallow tropical and subtropical waters, and occurs in both encrusting and branching colony forms. Their simple morphology and morphological plasticity have hindered taxonomic understanding of this genus. In this study three morphologically distinct types (= type-1, -2, and -3) of Briareum from the Ryukyu Archipelago and their genetic diversity were examined. Colony, anthostele morphology, and sclerite length were examined for each type. Four molecular markers (mitochondrial cytochrome c oxidase subunit 1, mitochondrial mismatch repair gene, nuclear 18S ribosomal DNA, internal transcribed spacer 2 (ITS2)) were used to evaluate molecular phylogenetic status of these variations. Although one morphological type ("deep" small colonies, = type-3) showed small differences in nuclear ITS2 sequences compared to the other two types, the remaining types had identical sequences for all molecular markers examined. The results suggest extremely low genetic diversity despite highly variable morphology of Briareum species in Okinawa. Nevertheless, considering the distribution patterns and discontinuous morphology of type-3 compared to the other two morphotypes, genetic isolation of type-3 is plausible. In Briareum, small variances in nuclear ITS2 sequences of type-3 may have much more importance than in molecular phylogenies of other octocorals. Further phylogenetic investigations and comparison with Briareum specimens from other regions are necessary to conclusively taxonomically identify the three types.

Overview of the genus Briareum (Cnidaria, Octocorallia, Briareidae) in the Indo-Pacific, with the description of a new species

“…The one from the Red Sea identified by Prof. Benayahu represents Briareum hamrum . Miyazaki and Reimer (2014), who used other DNA markers and examined specimens from southern Japan, found three different morphological types of Briareum which seemed to be similar genetically and the authors suggested further analysis to reveal the phylogenetic relationships of these three types. Probably their material now can be identified with the morphological findings presented here.…”

“…Although molecular records from the Indo-Pacific are rare, Briareum is distinctly recognized as one of the basal genera in the Octocorallia phylogeny (McFadden et al 2006). The current records suggest the existence of at least three different species of Briareum across the Indo-Pacific region (McFadden et al 2011, 2014; Miyazaki and Reimer 2014; GenBank (http://www.ncbi.nlm.nih.gov/genbank/). These data emphasize the need for further morphological and molecular knowledge about Briareum species across wider geographical areas.…”

Briarenolides K and L, New Anti-Inflammatory Briarane Diterpenoids from an Octocoral Briareum sp. (Briareidae)

“…A voucher specimen (NMMBA-TW-SC-2011-77) was deposited in the National Museum of Marine Biology and Aquarium. This organism was identified by comparison with previous descriptions [ 45 , 46 , 47 , 48 , 49 ].…”

“…In our continuing studies of this interesting organism, a sample collected at the Southern Tip, Taiwan, identified as Briareum sp. [ 45 , 46 , 47 , 48 , 49 ], yielded two new briaranes, briarenolides K ( 1 ) ( Scheme 1 and Supplementary Figures S1–S7 ) and L ( 2 ) ( Scheme 1 and Supplementary Figures S8–S14 ). In this paper, we report the isolation, structure determination and anti-inflammatory activity of briaranes 1 and 2 .…”

Briarenolides U–Y, New Anti-Inflammatory Briarane Diterpenoids from an Octocoral Briareum sp. (Briareidae)

“…A voucher specimen (NMMBA-TW-SC-2011-77) was deposited in the National Museum of Marine Biology & Aquarium. This organism was identified by comparison with previous descriptions [ 9 , 10 , 11 , 12 , 13 ].…”