Unraveling the interaction between hormones and incubation temperature on lizard cognition

Abstract

Cognition is crucial for survival and reproduction. However, developmental conditions like thermal environments or stress-related hormones can shape cognitive abilities by altering brain physiology or function. Here, I investigated how prenatal thermal environment and corticosterone (CORT) - a key stress hormone in reptiles - affects cognitive development in two species of skinks: the delicate skink (Lampropholis delicata), and the common garden skink (L. guichenoti).

I manipulated egg CORT levels and incubation temperature and then assessed lizards' performance across multiple cognitive domains, alongside mitochondrial physiology in brain regions involve in those cognitive processes. I found region-dependent effects of prenatal CORT and temperature on oxidative damage, but not on metabolic function. Nonetheless, mitochondrial physiology was not linked to cognitive performance. Data shows that most cognitive abilities - decision-making, detection of visual stimuli, behavioural flexibility, and spatial and associative learning - were resilient to early environmental conditions. However, CORT-treated L. delicata responded faster to prey-related chemical cues.

Our results suggest that cognitive traits in L. delicata and L. guichenoti are generally robust to variation in prenatal CORT and temperature. Alternatively, it is also possible that the levels or duration of prenatal exposure used in this study were not sufficient to elicit measurable cognitive effects, and that more extreme or prolonged exposure might yield different outcomes. Furthermore, the absence of link between mitochondrial physiology and cognition - despite strong associations reported in mammals - raises important questions about species-specific mechanisms underlying cognitive processes. Conversely, such associations may emerge or strengthen with time - due to cumulative oxidative damage -suggesting age-dependent effects of mitochondrial physiology on cognitive processes. Future studies should explore the mechanisms underlining cognitive resilience to CORT and temperature or the effects of prolonged exposure to these factors as well as the potential for age-dependent relationships between mitochondrial function and cognitive performance.