The present study characterizes the early stages of development of Brycon hilarii (Valenciennes, 1850) based on morphometric and meristic characters. Patterns of development in morphometric characters were analyzed through the fit of linear, quadratic and linear piecewise models. Samples were collected from March 2000 to March 2004 in basins of the Cuiabá and Manso rivers, state of Mato Grosso, Brazil. Larvae were identified and classified in different stages (Larval Yolk, Pre-Flexion, Flexion, and Post-Flexion) according to notochord development. The morphometric and meristic characters for each larva were, respectively, measured and counted. The standard length ranged from 3.25 to 26.00 mm. The Larval Yolk stage showed a greater concentration of dendritic pigments along the intestine, and the Flexion and Post-Flexion stages showed an intensified pigmentation intensified along the back. A single spot on the humerus and another on the caudal peduncle were observed at the end of the Post-Flexion stage. Also, in the Larval Yolk and Pre-Flexion stages. The intestine is long, the snout is short, the adhesive organ was present in the Larval Yolk and Pre-Flexion, and the mouth is terminal throughout the development. The total number of myomeres ranged from 41 to 50 (23 to 30 pre-anal and 16 to 24 post-anal). Number of fin rays: dorsal 11; anal 30; pectoral 15 and ventral eight. The analysis of the development indicated higher metamorphosis in the Flexion stage.
Morphology; larvae; fish; piraputanga; Paraguai river basin
