Prolonged larval development in anurans: Assessing the independence of somatic growth and gonadal differentiation in Odontophrynus cordobae (Odontophrynidae).

Abstract

Prolonged larval development in anurans provides an opportunity to examine how different developmental systems are temporally coordinated during ontogeny. In this study, we investigated larval development, somatic growth, and gonadal differentiation in the frog Odontophrynus cordobae under natural conditions. Field sampling throughout the annual reproductive period revealed the coexistence of two larval cohorts spanning a broad range of Gosner stages, indicating extended larval persistence and overwintering. Developmental sequences suggest that larval development may last between seven and nine months in natural populations. Morphometric analyses demonstrated progressive increases in total length, snout-vent length, body height, tail height, and interorbital width during larval ontogeny, with tail resorption occurring abruptly at metamorphic climax. Ovaries differentiated earlier and more gradually than testes, with developmental midpoints occurring at Gosner stages 32-33 and 34-35, respectively. Despite this temporal offset in gonadal differentiation, males and females exhibited similar somatic growth trajectories and no detectable sexual size dimorphism during larval development. These results indicate that somatic growth and gonadal differentiation follow partially independent temporal trajectories in O. cordobae. More broadly, our findings support the view that metamorphosis in anurans does not represent a strictly synchronized developmental transition, but rather the integration of partially independent ontogenetic processes differing in timing and dynamics.