Meeting Abstract
Males in the lizard genus Anolis erect a ridge of tissue along the dorsum, which increases their lateral profile during agonistic encounters. Though noted in behavioral studies, little attention has focused on the physiological regulation of these crests. We tested the physiological and behavioral conditions under which males erect crests. The β-adrenergic receptor agonist isoproterenol (ISO) initiated crest erections within 2-3 minutes of injection. Prior to histological examination, we hypothesized that vascular changes mediated crest erection through β- and α-receptor stimulation. Alpha-adrenergic receptor agonists failed to inhibit crest erections and the β-receptor antagonist propranolol (PRO) delayed, but did not inhibit the onset of ISO-induced crests. We used mirrors to simulate male aggressive encounters and initiate dorsal crest development. Under these conditions, crest erections occurred in a time frame similar to the ISO-induced crests. However, injection of PRO prior to the mirror encounter completely inhibited crest erections, though all other agonistic behaviors (dewlap pulsing, lateral display, approach, etc.) were intact. Histological examination of the erect crest tissue indicated that an increase in extracellular fluid caused the increase in tissue volume, suggesting an inflammatory-like response. In separate experiments we used indomethacin (a prostaglandin synthesis inhibitor) or Na-cromolyn (a mast cell inhibitor) to inhibit ISO-induced crest erections. Neither approach inhibited the crest erections nor did we find evidence that leukocytes invaded the tissue 30, 300, or 600 minutes following crest induction. These lizards appear to use a mechanism for crest erection previously not described in a social signaling context.
