Abstract

This study documents the first records of the family Cuthonellidae and the genera Cuthonella and Tenellia from Korean waters. Five nudibranch species previously unrecorded in Korea were identified: Cuthonella georgstelleri, Cuthona futairo, Tenellia melanobrachia, Tenellia zvezda, and Tambja morosa. Each species was redescribed based on distinctive morphological characteristics, and underwater photographs of living individuals were provided. To evaluate genetic divergence, mitochondrial cytochrome c oxidase subunit I (COI) sequences were analyzed for four of the five species. The calculated intraspecific p-distances were 0.6% in C. futairo, 0-1.5% in T. melanobrachia, and 0.6-1.7% in T. zvezda, while T. morosa exhibited considerably higher intraspecific variation (0.3-11.7%). These results offer a useful molecular reference framework for future integrative taxonomic investigations of nudibranchs in the Northwest Pacific.