Thecacera sesama sp. nov. (Nudibranchia, Polyceridae) from Taiwan, evident from morphology and phylogenetic analyses of the 16S rDNA and cytochrome c oxidase I gene

Thecacera sesama Chan 3 mm). Phylogenetic analyses of two mitochondrial genes, cytochrome c oxidase subunit I (COI) and 16S rRNA, confirmed it as a new species in Thecacera . The molecular data places Thecacera sesama sp. nov . as a sister species to Thecacera picta , with a significant interspecific COI divergence of 14.17%. This discovery highlights the rich, yet under documented, marine biodiversity of Taiwan and underscores the value of combining traditional morphological examination with molecular phylogenetics for accurate species delimitation in cryptic nudibranch lineages.