Ethological Aspects of Stress in a Model Lizard, Anolis carolinensis

Abstract

Research on the stress response in reptiles can provide a useful comparative perspective for understanding how the constituent elements of the response can be put into service of diverse behavioral adaptations. A summary of the neural and endocrine causes and consequences of specific behavioral patterns seen in the small diurnal lizard, Anolis carolinensis, has provided a model for the exploration of the dynamics of autonomic and neurohormonal contributions to adaptive behavior. In this species, changes in body color provide indices of the flux of circulating stress-relevant hormones, and are seen in situations from spontaneous exploration through agonistic behavior. Furthermore, captive adult males spontaneously and consistently manifest social dominance relationships that provide many of the elements of a stress-mediated adaptive behavioral patterns. These patterns include suppressed reproduction and long-term coping apparently based more on stress-mediated changes in motivation than acquired changes in behavior.

60 YEARS OF POMC: Melanocortin receptors: evolution of ligand selectivity for melanocortin peptides

“…In addition, chronic stressors will promote the release of ACTH from the anterior lobe of the pituitary that can also activate MC1R receptors on human melanocytes (Costin & Hearing 2007). This chronic stress response on integument color change by the anterior pituitary also appears to occur for an amphibian and a reptile (Greenberg 2002, Kindermann et al 2013.…”

Rapid body color brightening is associated with exposure to a stressor in anAnolislizard

“…Every A. aquaticus individual exposed to the stressor increased the percent luminance and hue of the eye stripe and lateral stripe between their initial state at capture (i.e., prior to an anticipated increase in plasma corticosterone and therefore a before-stress measurement; Moore 1991) and their final state (i.e., following field manipulation, which correlates with an increased plasma stress hormone concentrations in other species; Matt et al 1997). The relationship of stress and brightness exhibited in A. aquaticus is therefore at odds with the accepted paradigm in which stress induces dark coloration (reviewed by Greenberg 2002Greenberg , 2003. Glucocorticoids (corticosterone) and stress-relevant catecholamines are elevated following exposure to a stressor, and both are implicated in the darkening of body coloration (Greenberg et al 1984;Greenberg and Crews 1990;Summers and Greenberg 1994) through co-production of melanocyte-stimulating hormone (MSH) and corticotropin (ACTH) (Hadley and Goldman 1969).…”

“…These rapid changes in body coloration permit individuals to dynamically respond to predators (e.g., Stuart-Fox and Moussalli 2008;Langridge 2009;Kronstadt et al 2013), abiotic challenges (e.g., Fulgione et al 2014;Smith et al 2016), prey availability (e.g., Anderson and Dodson 2015), and conspecifics (e.g., Umbers et al 2013;Ligon 2014;Maruska 2015). Together, these color changes offer insight into, and have sometimes been used as proxies of, physiological or cognitive state (e.g., Yang et al 2001;Greenberg 2002;Plavicki et al 2004;Adamo et al 2006).…”

Memory of opponents is more potent than visual sign stimuli after social hierarchy has been established

“…Rank also appears to influence the responsiveness of eyespot expression to nonsocial stressors [62]. The confluence of timing for eyespot and body coloration presents different messages depending on rank [21][22][23]40,69,70]. A darkened eyespot on a proactive dominant green male inhibits aggression and stimulates catecholamine release [36,40,69,70].…”

“…Therefore, formation of the eyespot signal plays a role in aggression [38], rank formation [40] and social stability [70]. This contextually plastic social sign stimulus is controlled by epinephrine and norepinephrine (NE) from the adrenal gland and sympathetic nerve terminals, which binds to β 2 -adrenergic receptors to cause darkening of postorbital skin while the rest of the body remains green [16,22,25,83]. More rapid eyespot darkening corresponds with more rapid production of high intensity aggression, which facilitates dominant social status [34,40,[69][70][71].…”