External Morphology of Leporinus oliveirai (Characiformes: Anostomidae) During Early Life Stages.

Leporinus oliveirai is a recently described species from Serra do Cachimbo, Pará State, Brazil, notable for its small size and vibrant coloration. This species has been successfully reproduced in captivity and is commercially traded internationally. Herein, we describe the early development of Leporinus oliveirai, documenting its external morphology with photographs and illustrations. The ontogeny of L. oliveirai is compared with that of other anostomids for which ontogenetic data are available, and developmental patterns are described for the family. In Anostomidae, the critical processes associated with the transition to exogenous feeding occur within the first 5 days post-hatching. Fin formation occurred in two distinct phases: the anal, dorsal, caudal, and adipose fins developed first, followed by the pelvic and pectoral fins. The sequence of fin ossification in anostomids is generally consistent with patterns described for other Characiformes. Additionally, a marked increase in growth rate and indications of allometric growth were observed following notochord flexion.