Aggressive but not reproductive boldness in male green anole lizards correlates with baseline vasopressin activity

Abstract

Across species, individuals within a population differ in their level of boldness in social encounters with conspecifics. This boldness phenotype is often stable across both time and social context (e.g., reproductive versus agonistic encounters). Various neural and hormonal mechanisms have been suggested as underlying these stable phenotypic differences, which are often also described as syndromes, personalities, and coping styles. Most studies examining the neuroendocrine mechanisms associated with behavioral boldness examine subjects after they have engaged in a social interaction, whereas baseline neural activity that may predispose behavioral variation is understudied. The present study tests the hypotheses that physical characteristics, steroid hormone levels, and baseline variation in Ile3-vasopressin (VP, a.k.a., Arg8-vasotocin) signaling predispose social boldness. Behavioral boldness in agonistic and reproductive contexts was extensively quantified in male green anole lizards (Anolis carolinensis), an established research organism for social behavior research that provides a crucial comparison group to investigations of birds and mammals. We found high stability of boldness across time, and between agonistic and reproductive contexts. Next, immunofluorescence was used to colocalize VP neurons with phosphorylated ribosomal protein S6 (pS6), a proxy marker of neural activity. VP-pS6 colocalization within the paraventricular and supraoptic nuclei of the hypothalamus was inversely correlated with aggression boldness, but not reproductive behavior boldness. Our findings suggest that baseline vasopressin release, rather than solely context-dependent release, plays a role in predisposing individuals toward stable levels of aggressive boldness toward conspecifics by inhibiting behavioral output in these contexts.

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

“…Intrinsic factors, such as hormones, present associations with animal personality and individuals that are relatively bolder may also present relatively high hormone levels . Testosterone has been shown to increase an individual's boldness behaviour (e.g., Raynaud & Schradin, 2014) and there is an association between boldness behaviour and testosterone receptors presence (Kabelik et al, 2022). In lizards, testosterone can activate the secretion of femoral glands in adults of both sexes (Hews & Quinn, 2003).…”

Efeitos do aumento de temperatura e estresse térmico prolongado na fisiologia e comportamento da rã-touro (Lithobates catesbeianus): correlações entre a fisiologia do estresse e personalidade animal

“…: genetic, epigenetic, physiological, neurobiological) that give rise to this behavioural consistency are still notably understudied . Specifically regarding endocrine underlying mechanisms, research has mostly focused on mammals and birds, with few studies on teleosts (Fürtbauer et al, 2015) and lizards (Kabelik et al, 2022). One concept that emerges in this literature is that of coping styles, which integrates consistency in both behavioural and physiological stress response variables (Koolhaas et al, 1999).…”