Skin Deep: Potential Thermoregulatory Role of Osteoderms in Alligator Mississippiensis

Event Center BC

The American alligator, Alligator mississippiensis, is recognized by its striking appearance of having “spikes” on its dorsal side. These “spikes” are called osteoderms which are scales composed of bone. Alligators belong to a clade called Archosauria and are the most closely related species to dinosaurs that are currently living. Through fossilized records, it is widely accepted that dinosaurs were found to have bony plates that resemble those of osteoderms. It has been speculated that these plates may have had some function in thermoregulation (Main 2005). Osteoderms in alligators are vascularized and can obtain blood flow from the body (Vickaryous 2008). These vascularized areas are thought to play a role in regulating body temperature, considering the ectothermic and poikilothermic metabolism of crocodilians. We used thermal infrared imaging as a noninvasive tool to determine the surface temperature of the alligator body (Tattersall 2010). By manipulating the environmental conditions that the alligator was exposed to, we recorded variation in the alligator’s surface temperature with infrared cameras. Simultaneously, we tracked the alligator’s core temperature with a cloacal thermocouple. We subjected cold-acclimated (15°C) juvenile alligators to warming conditions (35˚C) in vivo and ex vivo. We found that live alligators showed a faster rise in core temperature than their carcass. We also found that live animals’ core temperature exceeded their surface temperature, a feat impossible when blood flow to the skin was stopped. Finally, we found that osteoderm surface temperature was lower than that of neighboring scales. All three results are strong evidence that vascularized osteoderms play an important role in thermoregulation in warming crocodilians.