Faculty Advisor

Rick Adams

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The evolution of flight has resulted in adaptive changes in the appendicular skeleton of bats. Although forelimb development is well-studied, little is known for hindlimb even though it helps support the wing membrane. Seba’s short-tailed bats (Carollia perspicillata) are New World fruit bats (Phyllostomidae, Microchiroptera) that reside throughout South and Central America. Our hypothesis was that the growth and development (ontogeny) of the hindlimb in bats will differ from terrestrial mammals (mouse) due to the adaptive demands of flight. Ten developmental stages of C. perspicillata were differentially stained using alcian blue (cartilage) and alizarine red (bone). Greatest length measurements (mm) were taken of the femur, tibia, and skull using an Olympus microscope with ocular ruler. For comparative measures with an ancestral terrestrial mammal, data on mouse femur, tibia, and skull lengths were gathered from the literature. Regression analysis for growth of the femur and tibia in mice compared to skull length showed a slope of 0.75 (R2 = 0.97) and 0.74 (R2 = 0.99) respectively. Carollia perspicillata showed a lower slope for femur (0.49, R2 = 0.87) and tibia (0.49, R2 = 0.88) growth indicating that the hindlimb grows at a slower rate (negative allometry) relative to the skull in bats than in mice. Regressing tibia and femur lengths against each other showed that the growth rate (slope = 0.95, R2 = 0.94) of the femur to the tibia had negative allometry with the tibia outpacing the femur, whereas C. perspicillata showed a positive allometric growth rate (slope = 1.1, R2 = 0.98) indicating that femur growth outpaced tibia growth in bats. These data indicate that the ontogeny of the hindlimb in bats has shifted away from a more ancestral terrestrial mammal due to selective pressures around the evolution of flight.