Amerotyphlops brongersmianus (Vanzolini, 1976) (Typhlopidae, Serpentes) as a model for scolecophidian ontogenetic shifts of heart topography and relative size

摘要

Ontogenetic shifts in the snake heart topography are mostly associated with their life habits and physiological adaptations due to modifications of complex functional-adaptative and developmental constraints. However, such studies are incipient for scolecophidians, and the presence of shifts putatively related to physiological mechanisms are still unexplored for this group. We aimed to evaluate the presence of topological shifts in heart position and the allometry of heart/chambers total length in Amerotyphlops brongersmianus. Our results indicate that there is a craniad ontogenetic shift of the heart position related to total length increase. Heart total length and their chambers also grow isometrically in relation to head and total body length. We discuss the possible functional and evolutionary perspectives of our results with comparison to data available for alethinophidan snakes. We hypothesize the anterior displacement of organs possibly remains as an ancestral state to compensate reproductive constraints imposed by the ancestral scolecoid miniaturized body.