Harutaka Hata, Sébastien Lavoué & Lauren Sallan

Abstract. Ilisha brachysoma (Bleeker, 1852), previously regarded as a junior synonym of Ilisha melastoma (Bloch & Schneider, 1801), is shown to be a valid species and is redescribed on the basis of seven specimens from Indonesian waters from Sumatra to Bali, including the previously designated holotype. Although I. brachysoma and I. melastoma share multiple morphological traits, including a deep body, the form of the swim bladder, the shape of the body scales and caudal fin, and almost same numbers of gill rakers and ventral scutes, I. brachysoma can be distinguished from I. melastoma by several features, including having a higher anal-fin ray count (total anal-fin rays 46 or 47 vs. 36–43 in I. melastoma) and a longer anal-fin base (40.1–43.4% of SL vs. 32.2–37.9%). In addition, both species differ from each other by a mean uncorrected mitochondrial COI genetic distance of 10.7%. In this study, we also examine and redescribe I. melastoma; we confirm that the species is widely distributed in the Indo-West Pacific from the Persian Gulf to Indonesia and Taiwan, and exhibits very low genetic differentiation throughout its distributional range, further suggesting reproductive separation from I. brachysoma despite shared morphology and limited contact between the populations on the northern coast of Indonesia. To stabilize the taxonomic status of nominal species related to I. melastoma, the holotype of “Clupea” melastoma is herein designated as the neotype for Platygaster verticalis Swainson, 1838, Clupea (Pristigaster) indicus Swainson, 1839, and Pellona ditchoa Valenciennes, 1847, the latter three nominal species becoming junior objective synonyms of C. melastoma.

Key words. Actinopterygii, Ilisha striatula, Pellona ditchela, Sunda Islands, taxonomy

Read article here: RBZ-2025-0034