Anew bitterling, Rhodeus pseudosericeus sp. nov., is described on the basis
of 31 specimens from five localities included in the Namhan River system,
South Korea. The new species is distinguished from other Rhodeus species by
the following combination of characters: branched dorsal fin rays 9-10 (mo
de 9); branched anal fin rays 9-11 (mode 10); longest simple ray of dorsal
fin strong and stiff, distally segmented; pelvic fin rays i, 6-7; iris of m
ales blackish; dorsal and anal fins of males grayish in breeding season; ka
ryotype with 2n = 48 (8m + 20sm + 20st). Rhodeus pseudosericeus sp. nov. is
similar to Rhodeus sericeus sericeus in the number of pelvic fin and branc
hed dorsal fin rays and the melanophores present on the dorsal fin membrane
, but differs from the latter in having a greater body depth, more branched
anal fin rays, fewer vertebrae, a lower number of scales in the lateral se
ries, and differing male nuptial coloration.