Validity and redescription of the poorly known Japanese blenny Alticus orientalis Tomiyama 1955 (Perciformes: Blenniidae)

Abstract

The poorly known blenny Alticus orientalis Tomiyama 1955 is considered a valid species and redescribed on the basis of 73 specimens (36 males and 37 females), 20.5–83.5 mm in standard length (SL). The species is characterized by the following combination of characters: dorsal-fin spines 14 (rarely 13); pectoral-fin rays 15 (very rarely 14 or 16); pelvic-fin rays I, 4; caudal-fin rays 12 (very rarely 11); supraorbital cirrus finely branched (except in specimens < ca. 20 mm SL); canine-like teeth absent on lower jaw; 1–9 small conical teeth on vomer (rarely secondarily lost); 3 (very rarely 2) pores in mandibular series; pre-anal-fin length 37.6–43.2 (mean 40.4) % SL in males, 39.9–46.9 (43.0) % SL in females; caudal-fin length 19.0–24.2 (21.8) % SL in males, 19.7–25.2 (22.4) % SL in females; pre-anal-fin length / caudal-fin length 1.6–2.2 (1.9) in males, 1.8–2.2 (1.9) in females; cheek without black spots; and head and pectoral fin without small black dots. Although A. orientalis is most similar to Alticus montanoi (Sauvage 1880) [all Japanese specimens previously identified as Alticus saliens (Lacepede 1800) are actually this species], it can be distinguished from the latter by the presence of teeth on the vomer, a greater number of pores in the mandibular series, greater pre-anal-fin length, and slightly shorter caudal-fin length. In addition, genetic analysis supports the divergence of A. orientalis from available sequences from other species of Alticus. In Japanese waters, A. orientalis is distributed around (and probably endemic to) the Izu and Ogasawara islands, whereas A. montanoi is distributed in the Ryukyu and Daito islands.