Supplementary description and molecular analysis of Stiphodon hadiatyae (Teleostei, Gobioidei, Sicydiinae) from Enggano Island, Indonesia

The present study provides a supplementary morphological description, the first molecular analysis, and the first description of female of Stiphodon hadiatyae Nurjirana, Gustiano, Haryono & Wibowo, 2025. In addition, the first distributional record of the species from outside Enggano Island is noted, based on underwater photographs from Padang, Sumatra, Indonesia. Although recently described, the original account lacked both molecular data and female diagnostic characters.

Phylogenetic and morphological evidence confirms placement within the “ Stiphodon sapphirinus group ” characterized by generally having 14 pectoral fin rays and a smaller adult body size (usually <40 mm SL). Stiphodon hadiatyae differs from its congeners by the following characteristics: males possess a pointed first dorsal fin, with an elongated, filamentous fourth spine, fewer premaxillary tricuspid teeth, a belly entirely covered by cycloid scales, and a slightly pointed caudal fin.

Coloration also distinguishes both sexes from congeners: males with a blue head with a brown snout, body greyish, median fins orange, and a distinct black blotch at caudal fin base; females with orange to red first, second dorsal, and anal fins, and a caudal fin proximally red to orange with four or five rows of brown spots.