Morphometrics and ratio of body proportionality of tadpoles of Rhinella icterica (Anura, Bufonidae) at different developmental stages.

The plasticity of the anurans' development is probably related to their great ecological and geographic diversity. Therefore, the understanding of environmental occupation by tadpoles is related to their morphological peculiarities. We evaluated the morphologic development of the larval phases 23, 25, 30, 37, 39 and 42 of Rhinella icterica with the aim of establishing the ratio of growth, the increase in corporal mass in relation to growth and the isometry of the corporal variables for each evaluated stage. We submitted the corporal variables to the Multivariate Allometry and the relation between these variables was evaluated using the Principal Components Analysis. We verified the isometric growth and correlation between the different variables, evaluated the growth according to the body mass and established the proportionality ratio between the corporal regions. Each corporal region evaluated presented a fixed proportionality ratio, regardless of the stage, and the size of this portion was found when its proportionality index was multiplied by the tadpole's total length. This study demonstrates that the larval phase of R. icterica presents an isometric growth with proportional development of the corporal parts regardless of the evaluated stage.