Meeting Abstract
93.8 Monday, Jan. 6 15:15 Prehensile tail use in didelphid marsupials: functional modifications for terrestrial species RUPERT, JE*; BUTCHER, MT; Indiana University School of Medicine; Youngstown State University jerupert@iupui.edu
Locomotor behavior has largely been studied through analyses of limb kinematics, gait mechanics, and muscle architecture and fiber type. Evaluating these characteristics in extant mammals is helpful to determine ancestral form and provides insight into functional changes species have undergone. Families containing both arboreal and terrestrial species, such as didelphid marsupials, are particularly interesting because body size and gait mechanics have been modified to reflect use or disuse of rainforest vertical strata. Didelphids arose from a common arboreal ancestor, and yet all species retain prehensile digits, an opposable hallux, and a prehensile tail. Terrestrial opossums have overall larger body sizes and use lateral sequence gaits, but they do not require a prehensile tail for terrestrial locomotion. Our studies have analyzed the comparative structure and function of this specialized appendage between species of didelphids with opposing locomotor habits (i.e., arboreal vs. terrestrial). Using multiple muscle fiber typing techniques (e.g., SDS-PAGE, densitometry, immunohistochemistry) combined with anatomical measurements and behavioral observations, we find functionally different utilizations of the prehensile tail in didelphids associated with muscle physiology and locomotor habits. Species that have become habitually terrestrial use their tail for nest building and offspring manipulation, and have an overall slower fiber type distribution and reduced tail-to-body length ratio compared to arboreal species who use the tail extensively for balance, stability, and arboreal maneuvering. Our studies provide a foundation for future work relating tail function to locomotor behavior in other orders of mammals (e.g., non-human primates) that have either retained or lost tail prehensility.
