Histochennical properties of some jaw muscles of the lizard Tupinambis nigropunctatus (teiidae)

In many vertebrate limb and jaw muscles constituent fibers with differing contractile and metabolic properties are distributed so as to produce distinct intramuscular oxidative and glycolytic regions. The purpose of this investigation was to determine if similar compartmentalization exists in jaw muscles of the teiid lizard Tupinambis nigropunctatus. Nine jaw muscles from two adults and one juvenile were examined, and serial sections from each muscle were analyzed using histochemical techniques to indicate relative contractile, oxidative, and glycolytic capacities of the fibers and their patterns of distribution. Three distinct fiber types were observed. The histochemical profile of type 1 fibers most closely resembled that of tonic muscle fibers, while profiles of type 2 and type 3 fibers corresponded to those of fast‐twitch glycolytic (FG) and fast‐twitch oxidative (FO) fibers, respectively. Three muscles contained only type 2 (FG) fibers, and two muscles contained a noncompartmentalized mixture of all three fiber types. The remaining four muscles were distinctly compartmentalized, having a small, inneroxidative region containing primarily type 1 (tonic) and type 3 (FO) fibers and a larger, outer region consisting entirely of type 2 (FG) fibers. The possible relationships between fiber types, compartmentalization, and jaw function are discussed.