The Relationships of Locomotion to Differential Predation on Pseudacris Triseriata (Anura: Hylidae)

Abstract

Laboratory experiments, using the garter snake Thamnophis sirtalis as predator and the chorus frog Pseudacris triseriata as prey, show that metamorphosing anurans are captured more frequently by T. sirtalis than either premetamorphic tadpoles or postmetamorphic frogs. Stomach contents of wild-caught Thamnophis have similarly revealed more anuran prey in transformation than at earlier or later stages. The high susceptibility of transforming Pseudacris to snake predation appears to be a direct consequence of a body form not conducive to effective locomotion.The sustained swimming ability of premetamorphic and metamorphic P. triseriata was examined in the laboratory. It was found that until the eruption of the forelimbs, the larger a tadpole is, the longer it can maintain its position in a steady current. The length of the tail appears to be a positive factor in sustained swimming. Large hindlimbs do not appear to assist swimming and may increase drag. Tadpoles that have begun to metamorphose (forelimbs visible) demonstrate a greatly diminished ability to hold their position in a current.The maximum jumping distance of metamorphic and postmetamorphic P. triseriata was also examined in the laboratory. Individuals which have just begun to metamorphose cannot hop as far as individuals which have advanced through metamorphosis and lost their tails. Amputation of the tails from early metamorphic individuals demonstrates the retarding role that the tail has on saltatory locomotion. Additional features, such as maturation of the anterior appendages, may also account for an increased jumping ability observed in P. triseriata as they progress through metamorphosis.Anurans spend a disproportionately short time in metamorphic transformation. The rapidity of this transformation appears to be an adaptation minimizing the amount of time anurans spend in this most vulnerable form.

Effect of Ontogenetic Increases in Body Size on Burst Swimming Performance in Tadpoles of the Striped Marsh Frog,Limnodynastes peronii

“…Several other studies have also reported an increase in swimming velocity with increases in total length in premetamorphic tadpoles (Wassersug and Sperry 1977;Huey 1980;Wassersug and Hoff 1985;Brown and Taylor 1995;Parichy and Kaplan 1995). Huey (1980) found average swimming velocity in tadpoles of Bufo boreas positively correlated with tail length between stages 31 and 41.…”

“…In an unpublished study, Hoff (1987) reported that length-specific swimming velocities of anuran larvae generally decreased with increasing body length; however, scaling relationships differed between species, with the length-specific swimming velocity of at least one species of anuran larvae (Xenopus laevis) showing no influence of total length. Most locomotor studies of anuran tadpoles have concentrated more on the influence of ontogenetic changes in body shape and the consequences of their globose body shape rather than body-size effects on swimming performance (Wassersug and Sperry 1977;Huey 1980;Wassersug and Hoff 1985;Wassersug 1989;Brown and Taylor 1995;Liu et al 1996Liu et al , 1997.…”

Water Velocity Tolerance in Tadpoles of the Foothill Yellow-legged Frog (Rana boylii): Swimming Performance, Growth, and Survival

“…I that large tadpoles have significantly lower critical velocities than small tadpoles (Table 4.7). In Expt.I, mass was tightly correlated with developmental stage so it is unclear whether bigger tadpoles had poor performance maintaining position in the interstitial spaces among the rocks in the Brett chamber by virtue of their size, or because of morphological changes such as large hind limbs which can increase frontal drag on a stationary tadpole and decrease swimming performance (Dudley et al 1991, Wassersug andSperry 1977). In addition to the obvious external changes, later stages have internal changes including the development of lungs which affect buoyancy and hardwired neurological behaviors such as surfacing to reinflate lungs periodically in response to increasing CO2 concentrations (Gdovin et al 2006).…”

Locomotor performance of three sympatric species of sea kraits (Laticauda spp.) from Orchid Island, Taiwan

“…On the contrary, it might produce the worst performance. For example, metamorphosing tadpoles are most vulnerable to predators during the developmental transition (with legs and a tail) due to their worst escape performance (Wassersug and Sperry 1977;Crump 1984). Similarly, in horned beetles, intermediate morphologies are rare or absent from natural populations due to their inferior competition for mating (Madewell and Moczek 2006).…”