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.

Protein–lipid Association in Lizard Chemical Signals

“…Over the last 30 years or so, lizards have become a model species to investigate the evolutionary forces shaping vertebrate chemical communication (e.g., Alberts 1991 ; Alberts et al 1993 ; Martín and López 2000 ; Pruett et al 2016 ; Baeckens et al 2017 ; García-Roa et al 2017a , 2017b ; Campos et al 2020 ; Ruiz–Monachesi et al 2020 ; Baeckens and Whiting 2021 ; Mangiacotti et al 2021 ). The reason for its popularity is partly due to the pivotal role of the chemical sensory modality in this taxon, which is not only characterized by readily observable chemoreception behavior of lizards (i.e., tongue-flicking; Schwenk 1995 ; Baeckens et al 2017 ), but also by the occurrence, in most species, of epidermal glands in the cloacal region ( García-Roa et al 2017a ; Cole 1966 ), used for inter- and intra-specific signaling ( Martín and López 2014 ; Mayerl et al 2015 ).…”

Meta-analysis of Behavioural Research in Lizards Reveals that Viviparity Contributes Better to Animal Personality than Secretory Glands

“…Most lizard species are highly dependent on their chemosensory system (Mason & Parker, 2010) and possess chemical-emitting scents glands (exocrine glands), which secrete proteins and lipid-rich components (e.g., Mangiacotti et al, 2019).These glands are involved in various social interactions (Baird et al, 2015;Campos et al, 2017) and the number and diameter of these glands have been considered proxies for conspecific communication relevance (Martins et al, 2004;Baeckens, 2017;Ruiz-Monachesi et al, 2020). Baeckens and Whiting (2021) investigated the relationship between sociability and the evolution of chemical secretory glands and suggested that social grouping may drive investment in epidermal signalling glands in lizards.…”

“…Exploration is defined as an individual's tendency to move around in unfamiliar environments (i.e., neophilia; Réale et al, 2007). This pattern could be explained by the highinvestment signal hypothesis, where a poorly developed or absent chemical emissary system would be counterbalanced by an efficient receiving system and higher exploration behaviour (Ruiz-Monachesi et al, 2020. For instance, different Liolaemus species with few or no precloacal pores showed higher exploration behaviour than species with a greater number of precloacal pores (Ruiz-Monachesi et al, 2020).…”

“…This pattern could be explained by the highinvestment signal hypothesis, where a poorly developed or absent chemical emissary system would be counterbalanced by an efficient receiving system and higher exploration behaviour (Ruiz-Monachesi et al, 2020. For instance, different Liolaemus species with few or no precloacal pores showed higher exploration behaviour than species with a greater number of precloacal pores (Ruiz-Monachesi et al, 2020). Therefore, if the secretory glands are absent, individuals may perceive their environment as more novel when exploring, potentially contributing to the development of individual consistency in this behaviour.…”