Occurrence and ecological implication of a tropical anguillid eel, Anguilla marmorata, in Brunei Darussalam, Borneo Island

ABSTRACT Tropical anguillid eels account for two-thirds of the 19 species in Anguilla Schrank, 1798. However, information on the species diversity, geographical distribution, and life histories of the tropical eels is very limited. Recent studies suggested that morphological species identification of the tropical anguillid eels should be validated by molecular analysis for accurate identification. After surveying for three years, two anguillid eels were found in Brunei Darussalam, Borneo Island. They were firstly identified as Anguilla marmorata Quoy & Gaimard, 1824 using morphological analysis and further gene analysis of cytochrome c oxidase subunit I (COI) confirmed the species identification. This study is the first comprehensive description of A. marmorata in Brunei Darussalam, Borneo Island. Furthermore, it is also the first study to validate two anguillid eels collected from the tropical Bonin Islands of Japan as A. marmorata by means of morphological and COI analyses. The molecular phylogenetic tree and haplotype network analyses suggest that A. marmorata found in Brunei Darussalam would belong to the North Pacific population of the westernmost distribution.

摘要：现存鳗鲡属（Anguilla Schrank, 1798）共包含19个物种，其中热带鳗鲡占三分之二。然而，当前关于热带鳗鲡的物种多样性、地理分布及生活史的研究资料仍较为匮乏。已有研究表明，若要实现热带鳗鲡的精准物种鉴定，需通过分子分析对其形态学鉴定结果进行验证。本研究历经三年野外调查，在婆罗洲岛文莱达鲁萨兰国境内采集到两尾鳗鲡样本。研究人员首先通过形态学分析将其初步鉴定为花鳗鲡（Anguilla marmorata Quoy & Gaimard, 1824），后续通过细胞色素c氧化酶亚基I（cytochrome c oxidase subunit I, COI）基因分析进一步验证了该物种鉴定结果。本研究是首次针对婆罗洲岛文莱达鲁萨兰国境内花鳗鲡（A. marmorata）开展的系统性描述。此外，本研究亦是首次通过形态学与COI分析，将日本热带小笠原群岛采集到的两尾鳗鲡样本鉴定为花鳗鲡的相关研究。分子系统发育树与单倍型网络分析结果显示，文莱达鲁萨兰国境内采集到的花鳗鲡种群属于分布最西的北太平洋种群。