Early Ontogeny of Plesiopuntius bimaculatus (Bleeker, 1863): Embryonic Development and Comparative Perspectives Within Smiliogastrinae

ABSTRACT

The present study provides the first comprehensive account of the embryonic and larval ontogeny of Plesiopuntius bimaculatus , a smiliogastrine cyprinid distributed in peninsular India and Sri Lanka, together with observations on its reproductive biology. Captive spawning produced small, adhesive, demersal eggs (696.46 ± 23.72 µm) deposited on vegetation and gravel, with no parental care observed. Embryogenesis followed the characteristic teleost developmental sequence, including meroblastic cleavage, epiboly‐driven gastrulation, and sequential organogenesis, with hatching occurring approximately 16 h 15 min after fertilization at 27°C–28°C. Larvae hatched at 2.09 ± 0.08 mm total length and exhibited transient substrate adhesion, early swim bladder inflation, and the onset of exogenous feeding during the pre‐flexion stage. Regression analyses revealed strong linear relationships among selected cranial and body measurements ( R ²  = 0.944–0.99), indicating coordinated changes in these dimensions during ontogeny. An ontogenetic shift from a terminal to a subterminal mouth position was also observed during juvenile development. Comparison with published developmental data for other smiliogastrine cyprinids revealed a broadly conserved developmental sequence, alongside differences in egg size, hatching size, and reported embryonic duration. These comparisons provide a basis for investigating potential differences in developmental timing among smiliogastrine taxa; however, heterochrony cannot be established from the available data because incubation conditions and developmental‐stage criteria differ among studies. The findings expand knowledge of early development in P. bimaculatus and provide a foundation for further comparative research and captive‐breeding applications.