Revised diagnoses of the gudgeons Belobranchusbelobranchus and B.segura (Actinopterygii, Gobiiformes, Eleotridae).

Diagnostic characters distinguishing the gudgeons Belobranchusbelobranchus and Belobranchussegura were reassessed and found to be inconsistent, making it difficult to accurately identify them. Numerous specimens of both species were examined combining genetic (mitochondrial COI gene) and morpho-meristic analyses. Our findings demonstrate that B.belobranchus and B.segura can be reliably distinguished from each other based on revised diagnostic characters, including several morphometric features (interorbital width, jaw length, and caudal-peduncle depth) as well as distinct head, body, and fin coloration.