Meeting Abstract
39.4 Sunday, Jan. 5 08:45 Multiple perspectives of the functional divisions within the swimming muscles of the Asiatic water monitor (Varanus salvator) YOUNG, B.A.*; MOST, M.G.; DUMAIS, J.; JOHN, N.; LYONS, B.; MACDUFF, A.; REISER, P.J.; A.T. Still University; University of Massachusetts Lowell; University of Massachusetts Lowell; University of Massachusetts Lowell; University of Massachusetts Lowell; University of Massachusetts Lowell; Ohio State University byoung@atsu.edu
Varanus salvator is a semi-aquatic species in which aquatic propulsion is produced by undulations of the tail base. This study examined the functional contributions of three muscles that insert on the tail base; Caudofemoralis, Longissimus (an epaxial muscle), and Iliocaudalis (a hypaxial muscle). For consistency all of the work was performed on juvenile specimens with total body lengths between 90 – 130 cm. To explore the functional roles of these muscles, we performed bipolar emg coupled with high-speed digital videography, whole muscle physiology, work loops, enzymatic fiber typing, and molecular analysis of the contractile proteins. The temporal pattern of the emg signals, combined with their relationship to swimming speed, suggests that the Iliocaudalis is the primary propulsive muscle while caudofemoralis functions more in stabilization. This inferred functional split was supported by other findings: caudofemoralis has a significantly different contractile rate and force output profile, a different pattern of fatigue, and more slow-type MHC than the axial muscles. The longissimus and iliocaudalis have similar molecular composition and physiological properties; the activity pattern of the longissimus indicates that it is not playing a major role in tail propulsion. Examining this locomotor system using these diverse analytical approaches may provide insight into the physiological properties of reptilian muscle. Comparative analyses within Varanus could illuminate the pattern of physiological evolution within this functional system.
