Taxonomic review of the dottyback genus Pseudoplesiops in Japanese waters, with descriptions of two new species (Pseudochromidae: Pseudoplesiopinae)

Abstract

A taxonomic review of the dottyback genus Pseudoplesiops (Pseudochromidae: Pseudoplesiopinae) in Japan recognizes five species: Pseudoplesiops umbrosus sp. nov., Pseudoplesiops occasus sp. nov., Pseudoplesiops annae (Weber 1913), Pseudoplesiops immaculatus Gill and Edwards 2002, and Pseudoplesiops rosae Schultz 1943. Pseudoplesiops umbrosus (43 specimens, 11.0–24.6 mm in standard length: SL) and P. occasus (5 specimens, 21.5–26.6 mm SL) have previously been misidentified as P. rosae, all three species being distinguishable from congeners by the following combination of characters: scales with distinct circular and radial striae (surrounding the former); I, 22 or 23 dorsal-fin rays; I or II (rarely), 13–15 analfin rays; and 11 or 12 precaudal vertebrae. However, P. umbrosus is distinct in having the dorsal- and anal-fin membrane margins not or barely incised (vs. deeply incised between the fin rays in P. occasus and P. rosae), the orbital ridge margined with dark brown (except anterodorsally) (vs. a small dorsoventrally elongated black blotch just behind the eye), and greater numbers of dorsal- and anal-fin segmented rays (viz., usually 23 dorsal- and 14 anal-fin segmented rays in P. umbrosus vs. 22 and 13, respectively in P. occasus and P. rosae), in addition to several morphometric characters. Pseudoplesiops occasus differs from P. umbrosus and P. rosae in having a red or reddish-orange body and fins in fresh condition (vs. generally brown to yellow), and greater numbers of predorsal scales [viz., 9–11 predorsal scales and 4 or 5 predorsal scales anterior to anterodorsal parietal pores in P. occasus vs. 7 or 8 (usually 7) and 2 or 3 (2), respectively, in P. umbrosus; 7–10 (8) and 2 or 3 (2), respectively, in P. rosae]. The validity of the three species was also supported by an analysis of partial 12S ribosomal RNA gene sequences. Morphological changes with growth in P. annae and P. umbrosus, notes on morphological and color variations in P. annae, and the key to the Japanese species of Pseudoplesiops are also provided.