Ontogenetic changes in activity, locomotion and behavioural complexity in tadpoles
Résumé
Metamorphosis is a widespread developmental process that involves considerable changes in morphology, habitat
use, ecology and behaviour between early developmental (larval) stages and adult forms. Among amphibians,
anuran larvae (tadpoles) undergo massive morphological and ecological changes during their development, with
early stages characterized by somatic growth, whereas more conspicuous changes (i.e. metamorphosis) occur later
during development. In this study, we examined how locomotor and behavioural traits covary with morphology (body
size) and metamorphosis (hindlimb and forelimb development) across developmental stages in spined toad (Bufo
spinosus) tadpoles. As expected, we found that locomotion and behaviour undergo significant changes during tadpole
development. These changes are curvilinear across developmental stages, with a phase of increasing activity and
locomotion followed by a phase of stasis and/or reduction in locomotion and behavioural complexity. All the metrics
we investigated indicate that the peak of activity and associated behaviour is situated at a pivotal stage when
somatic growth decreases and significant morphological changes occur (i.e. hindlimb growth). Future studies that
aim to investigate determinants of locomotion should include developmental stages as covariates in order to assess
whether the sensitivity of locomotion to environmental variables changes across developmental stages.