Morphological and genetic analysis for the diversity conservation of rare species, Thamnaconus multilineatus (Tetraodontiformes: Monacanthidae).

Climate changes have altered biodiversity and ultimately induced community changes that have threatened the survival of certain aquatic organisms such as fish species. Obtaining biological and genetic information on endangered fish species is critical for ecological population management. Thamnaconus multilineatus, registered as an endangered species by the IUCN in 2019, is a Data Deficient (DD) species with a remarkably small number of habitats worldwide and no known information other than its habitat and external form. In this study, we characterized the external and osteological morphology of a T. multilineatus specimen collected from eastern Jeju Island, South Korea, in 2020. We also investigated the phylogenetic relationships among related fish species through complete mitochondrial DNA (mtDNA) analysis of the T. multilineatus specimen. The external and skeletal characteristics of T. multilineatus were similar to those of previous reports describing other fish of the genus Thamnaconus, making it difficult to classify T. multilineatus as a similar species based only on morphological characteristics. As a result of analyzing the complete mtDNA of T. multilineatus, the length of the mtDNA was determined to be 16,435 bp, and the mitochondrial genome was found to have 37 CDCs, including 13 PCGs, 22 tRNAs, and 2 rRNAs. In the phylogenetic analysis within the suborder Balistoidei, T. multilineatus mtDNA formed a cluster with fish of the genus Thamnaconus. This study is the first to report on the skeletal structure and complete mtDNA of T. multilineatus. Since the current research on T. multilineatus has only been reported on morphology, the results of this study will be utilized as important information for the management and restoration of T. multilineatus as an endangered species and significant fishery resource.