Redescription of three trapanian nudibranchs (Nudibranchia, Goniodorididae) from Korea with a key to the species

Three species belonging to the genus Trapania Pruvot-Fol, 1931 are redescribed from Korea in this paper: Trapania euryeia Gosliner & Fahey, 2008, T. japonica (Baba, 1935), and T. toddi Rudman, 1987. Among these species, T. japonica is newly added to Korean fauna. The genus Trapania is characterized by a pair of extra-rhinophoral appendages on each side of the head, tentacular foot corners, a pair of extra-branchial appendages present around the gill, radula formula N×1.0.1. and consists of denticulated teeth, triaulic reproductive system, and minute spines on the armed penis. Herein, synonyms of the genus Trapania are summarized through a detailed literature review and the diagnostic characters of the genus Trapania are provided. Three species of the genus Trapania from Korea are distinguished from each other based on the color of extra-rhinoporal appendages and extra-branchial appendages, ground color, and distribution range of the brown markings on the dorsal surface. A taxonomic key to the genus Trapania in Korea is provided. In addition, the morphological characteristics of three trapanian nudibranchs in Korea are described and detailed photos of living animal are provided.