A report of four unrecorded species of opisthobranch molluscs from Korea

We collected and taxonomically examined four species of opisthobranch molluscs included in the orders Pleurobranchomorpha and Sacoglossa from Korean coastal areas. Species in the order Pleurobranchomorpha are characterized by two cylindrical rhinophores, two oral tentacles on oral veil, and gill on the right side of body between the mantle and the foot (Coleman, 2008). This order is composed of 70 valid species from 12 genera in 2 families that are distributed across the world (Gofas, 2013). In Korea, only two species of Berthellina citrina (Rüppell & Leuckart, 1828) and Pleurobranchaea japonica Thiele, 1925 have been reported by Choe and Lee (1994) from this order. Animals included in the order Sacoglossa are small in size. They have well developed radula and mouth part for eating algae and have shell or lack shell (Gosliner et al., 2008). This order consists of 284 species from 29 genera in 10 families (Jensen, 2007). Only one species, Elysia ornata (Swainson, 1840) has been recorded with no description in Korean waters (Lee and Min, 2002). This study provided re-descriptions with photographs of four species included in the Pleurobranchomorpha and Sacoglossa that were newly reported to Korean opisthobranch fauna. As a result of the study, 4 species in 3 genera of 2 families in the order Pleurobranchomorpha and 3 species in 3 genera of 3 families in the order Sacoglossa have been reported for the Korean opisthobranch fauna.