Efecto del tamaño del hábitat en la supervivencia, desarrollo y crecimiento en renacuajos de Engystomops pustulosus (Anura: Leiuperidae) y Rhinella humboldti (Anura: Bufonidae)

Abstract

Tadpole survival is strongly influenced by environmental factors such as temperature, oxygen, food, larval density, water volume and pond drying. Tadpoles of Engystomops pustulosus and Rhinella humboldti develop in ephemeral habitats with strong differences in their size (space and water volume) around the city of Ibagué, Colombia, and at the campus of the University of Tolima. This work evaluates the effect of three habitat sizes (large, medium, and small) on the survival, development and growth of tadpoles of these species under laboratory conditions. We placed five plastic containers per treatment, and in each of them we added 4 g of soil and one macrophyte. Later, ten tadpoles at stage 25 were added. Every twenty days we measured the survival, developmental stage, and total length of tadpoles. The experiments ended when all tadpoles completed metamorphosis or died. In both species we found similar results. Tadpole survival was significantly greater in the large habitat than in the medium and small habitats at 120 days for E. pustulosus, and at 80 days for R. humboldti (Logistic regression, p < 0.01). However, survival to reach metamorphosis was less than 50% for all treatments. After 20 days for E. pustulosus and 30 days for R. humboldti (Anova, p < 0.01), the development and growth of tadpoles were also significantly higher in the large habitat than the medium and small ones. Our results are contrary to other studies with tadpoles from ephemeral habitats that accelerate their developmental rate and metamorphose at a minimum body size. We conclude, therefore, that under natural conditions, tadpoles of E. pustulosus and R. humboldti will have less chance of survival in small temporal ponds with lesser availability of both space and water.