Meeting Abstract
Male lizards of the genus Anolis use a variety of dynamic morphological modifiers to enhance social signaling. Colorful dewlaps, skin color changes, and dorsal crest erections are used by many species during behavioral interactions. Previous investigators have described interesting details of coloration and dewlap function, but the morphological and physiological dynamics of dorsal crest erections have been largely ignored. We initiated studies to understand the tissue-level mechanisms behind the erection of this behaviorally relevant structure. We examined the dorsal crests under light microscopy with and without stimulation by the β-adrenergic agonist isoproterenol in both males and females of two anole species, Anolis sagrei and Anolis carolinensis. We hypothesized that crest erection was mediated through either subcutaneous muscle contraction or hemotumescence, two physiologically mediated mechanisms used by a variety of vertebrates. Histological examination revealed no evidence of gross vascular changes (e.g. sinusoid filling) or the presence of associated muscular tissue, forcing us to reject our original hypotheses. The crests appear to become erect through an increase in interstitial fluid within an encapsulated organ just under the skin. Edema causes the volume of the “crest organ” to increase and the vertically oriented structure maintains its shape with what appear to be horizontally arranged collagen fibers. As the crests begin to deflate, edematous fluid appears to move into spaces lateral to the crest capsule, diminishing the amplitude of the crest. The mechanism of the crest erection is currently unknown, but preliminary results suggest that it is neither prostaglandin nor mast cell mediated. Adult females of both species appear to lack the crest organ entirely.
