Unravelling associations among chemosensory system components in Liolaemus lizards

Abstract

Morphology can be associated with different aspects of an organisms’ life and the size of sensorial organs may allow inferences on the relevance of sensorial systems employed by them. There are organs implied in signal detection (sensory organs) and production (emitting organs) that are linked frequently to behaviour. Lizards are mostly dependent on the chemosensory system, where the vomeronasal organ (VNO) detects chemical scents delivered by the tongue from glands. The VNO, tongue flicks and glands, should be associated under a morpho-functional paradigm, and our main aim is to explore whether there is an association among these three chemosensory components in Liolaemus lizards. Additionally, tongue flicks have been used to evaluate the interaction between the chemical and visual sensory systems, showing a positive association. Hence, considering the close association between morphology and behaviour, our second aim is to explore whether the morphological (VNO, glands) and behavioural (tongue flicks) chemosensory components are correlated with eye size. We studied the rate of tongue flicks exhibited under two conditions, own scents and control, in 13 Liolaemus species and measured their head length, snout volume (VNO proxy), eye surface, and counted their number of precloacal glands. The rate of tongue flicks correlated positively with the residuals to head of snout volume and negatively with the number of precloacal glands, suggesting that they are associated and that this behaviour links both structures. In addition, residuals of snout volume and the rate of tongue flicks were positively associated with the residuals of eye surface, suggesting that chemical and visual sensory modalities would have co-evolved in these Liolaemus species. Our results show the importance of morphology and behaviour to infer the relevance of animals’ sensory systems.