Meeting Abstract
25.1 Friday, Jan. 4 Sexual dimorphism in courtship and copulatory neuromuscular systems of Anolis lizards JOHNSON, M. A.*; WADE, J.; Michigan State University; Michigan State University micheleajohnson@gmail.com
To reproduce, many animals must perform both courtship and copulatory behavior. However, the neuromuscular systems that control these two types of behavior have rarely been investigated in the same vertebrate taxa. Anolis lizards offer an opportunity to examine both behavioral systems, as these lizards perform elaborate courtship displays, males possess copulatory organs (hemipenes), and decades of previous behavioral research provides important information on the use of courtship and copulatory behavior in both natural and experimental settings. The green anole, Anolis carolinensis, has become a model species for studies of sexual behavior. Males of this species have large colorful throat fans, called dewlaps, extended during headbob and pushup displays in aggressive and courtship encounters; females have much smaller, less frequently used dewlaps. In parallel, males and females differ considerably in the size and composition of muscle fibers that control dewlap extension, and the soma sizes of motoneurons that inervate these muscles. Male-biased sexual dimorphism in the muscles and motoneurons that control hemipene eversion is even greater. Further, frequently-displaying males have larger muscle fiber and amydala soma sizes and greater physiological sensitivity to testosterone than infrequently-displaying males. We are now investigating sexual dimorphism in the courtship and copulatory neuromuscular structures of other Anolis species, including one species in which there is little sexual dimorphism in dewlap size (A. valencienni) and other close relatives of this species that exhibit high dimorphism in dewlap size and use similar to that seen in A. carolinensis. These studies will contribute to our understanding of how changes in the nervous system influence the evolution of reproductive behavior.
