Anurans diverged from more generalized amphibians over 250 million years ago. Extant anurans represent over 6000 species and are considered cosmopolitan. The basal-most anuran taxon is the Family Leiopelmatidae, which is comprised of Tailed Frogs and New Zealand Frogs. This clade diverged from all other extant anurans (Lalagobatrachia) over 200 million years ago, prior to the breakup of Pangaea. All anurans can be distinguished by their unique morphological characteristics including: elongation of the hindlimbs, shortened trunk with loss of vertebrae, fusion of caudal vertebrae into a novel structure known as the urostyle, flexible ilio-sacral joint, and absence of a tail.
Terrestrial jumping in frogs involves rapid hindlimb extension leading to loss of forelimb contact. During typical anuran landing, forelimbs make initial contact with the substrate, forming a pivot that helps with stabilization and support. Simultaneously, the hindlimbs are rotated under the body so that the frog is in position to initiate another jump. However, leiopelmatid frogs are characterized by a "bellyflop" landing, with retracted forelimbs and delayed hindlimb recovery.
It has been hypothesized that jumping evolved in a riparian context, with the ancestors of frogs leaping into water to flee terrestrial predators. If correct, the terrestrial bellyflop landing of leiopelmatids, which appears to be an aquatic diving behavior, may reflect the ancestral condition for the group. Describing the variation in jumping behavior among extant anuran taxa may elucidate the evolution of jumping. Therefore, I conducted a comparative study of aquatic landing behavior in three taxa spanning the anuran phylogeny, including the leiopelmatid Rocky Mountain Tailed Frog, Ascaphus montanus; the basal lalagobatrachian Fire-bellied Toad, Bombina orientalis; and the derived lalagobatrachian Northern Leopard Frog, Lithobates pipiens. I hypothesize that aquatic landing in leiopelmatids and lalagobatrachians is generally similar to terrestrial bellyflop landing in Ascaphus montanus.
Comparison of aquatic landing locomotion involved filming Ascaphus montanus, Bombina orientalis, and Lithobates pipiens jumping into water at 250 fps with synchronized high-speed video cameras. Frogs were placed on a jumping platform located within the aquarium and then stimulated to jump into the water by tapping immediately behind the animal. Landmarks were digitized and a series of kinematic, timing, and performance variables (e.g., angles, durations, velocities, etc.) were taken from each sequence to describe and compare the three-dimensional movements of the limbs and body. The kinematics of aquatic landing were then compared statistically among species as well as within species, in order to evaluate differences between aquatic and terrestrial landing behavior.
During aquatic jumping, Ascaphus montanus kept their hindlimbs extended and forelimbs retracted throughout the jump terminating in a bellyflop landing. Both Bombina orientalis and Lithobates pipiens exhibited hindlimb flexion during the aerial phase, while simultaneously protracting and adducting the forelimbs prior to contact with the water. In terrestrial landing, Bombina orientalis and Lithobates pipiens exhibited forelimb adduction resulted in a forelimbs-first landing and hindlimb flexion simultaneously. However, Ascaphus montanus exhibited delayed hindlimb recovery with the forelimbs remaining retracted throughout the jump. Comparing the aquatic and terrestrial contexts, there were no significant differences in relative jump distances among the three species; although, absolute jump distances were significantly longer in L. pipiens. The kinematics of terrestrial jumping in A. montanus, B. orientalis and L. pipiens were generally similar to that of aquatic jumping. However, all variables compared were shorter degrees in the aquatic context while being at a higher degree with respect to terrestrial context.
|Advisor:||Essner, Rick L.|
|Commitee:||Brunkow, Paul E., Jennings, David|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 53/06M(E), Masters Abstracts International|
|Subjects:||Morphology, Ecology, Evolution and Development, Zoology, Physiology|
|Keywords:||Ascaphus, Bombina, Lalagobatrachia, Leiopelmatidae, Locomotion, Rana|
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