Male A. sagrei with dewlap extended and dorsal crest raised. Image from wikipedia.org.

SICB 2015: What Causes Dorsal Crest Erections in Anoles?

We’ve all seen anole lizards extend their dewlaps, but the social displays of the many species of anoles also include the erection of a dorsal crest. But, what underlies the formation of these crests? Although many of us have talked about this, undergraduate John Ficklin, along with Morgan Gerace and Dr. Matthew Rand, all of Carleton College, aimed to find out and presented their work today at SICB. By injecting Anolis sagrei and A. carolinensis lizards with isoproterenol (a β-adrenergic agonist), they caused crest erection in males, but not in females. They then used histological techniques to examine the cellular morphology of the crest. What they discovered is that male anoles have a clearly-defined organ they dubbed the “crest capsule” (a structure female anoles lack), and when this capsule is filled with an edema from local blood vessels, the crest extends vertically. Collagen fibers appear to help maintain the crest’s vertical orientation during its display.  After inflation, the edema then drains into the subcutaneous space surrounding the capsule, causing the crest to deflate. They found no evidence of the involvement of muscles, cartilage, or vascular sinus in crest erection.

In sum, John Ficklin and his colleagues have solved one of the big questions of anole display!

4 thoughts on “SICB 2015: What Causes Dorsal Crest Erections in Anoles?

    1. the green anole in the photo is exhibiting a partial crest erection, not quite half way to a full crest. the brown anole is not displaying a crest erection at all. they can develop very large crests. of course there is bound to be substantial variation among populations, islands, and species.

  1. Thanks for posting this.
    My husband called us out yesterday to see an anole in our yard with a very large crest erection. We had no idea what we were looking at and thought that it was an entirely different species of lizard.
    Your post completely answered our questions. Thanks!

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