Plasticity in grow Rates and Size at Metanorphosis of Bufo paracnemis (Amphibia:Bufonidae) in a population of Argentina

KEHR, ARTURO I.; MARANGONI, F.

Praga, República Checa

Congreso; Third Worls Congress of Herpetology; 1997

Resumen: Intrapopulation variation in growth and body size at metamorphosis of Bufo paracnemis tadpoles in natural conditions. Two B. paracnemis clutches localized in opposite places were observed in a permanent pond in Corrientes Province, 20 km from its capital city, Argentina. After hatching, we recorded body length and stage of each tadpole. The main objectives were to analyze the covariation between length of larval period and size at metamorphosis, and to determine the length of larval life cycle for this first cohort born at the end of the winter. We checked the two places two days each during larval stages and daily since the discovery of the first metamorphs. Twenty one samples (20 tadpoles approximately) of each school were taken in both places between 8/29/95 and 10/12/95. The more important results were: 1) the tadpole body length was statisticaly different between both places. The body size of tadpoles in the place 1 (substrate with sand and without gramineous vegetation) reached smaller length than tadpoles of the place 2 (with organic matter as substrate and vegetation); 2) the size at metamorphosis was negatively correlated with length of the larval period in both places; 3) the size at metamorphosis also differed significantly between both places being greater in the place 2, and 4) the larval life cycle of B.paracnemistadpoles, for this cohort, was 39.6 ± 2.5 days. Due to the pond size, we suppose that gradual desiccation was the principal factor on tadpoles developing.