LANDBERG, T.*; AZIZI, E.; Univ.of Massachusetts Amherst: Aquatic escape performance through ontogeny and metamorphosis of spotted salamanders, Ambystoma maculatum

Spotted salamanders begin development inside a gelatinous egg mass and then hatch as larvae into ephemeral aquatic habitats where they grow and metamorphose into terrestrial adults that eventually return to water to breed. Throughout this complex life history, an individual will encounter different types of aquatic predators while their locomotor morphology undergoes continuous changes in size and shape. We reared Ambystoma maculatum in the laboratory at 23�1°C and sampled morphology and escape performance from late-stage embryonic (n=11), larval (n=40), metamorphosing (n=23) and young adult (n=15) salamanders to study how escape behavior changes over several life stages and a six-fold increase in size. We predicted that escape performance would peak early in ontogeny when locomotor morphology has matured and predation risk remains high. We also predicted that dramatic restructuring of musculo-skeletal, dermal and sensory organ systems would interfere with the locomotor performance of metamorphosing animals. As salamanders grew, the tail became gradually more elongate and tail area was greatest during the larval period. Escape responses consisted of a high-curvature preparatory stroke and a propulsive stroke that propelled salamanders away from the stimulus. Escape response duration, angular velocity during stage 1 and swimming speed during stage 2 all had performance peaks early in the larval period. Larvae had significantly higher escape performance than similiarly sized adults, but metamorphosing animals did not show a dramatic reduction in swimming performance. The duration of metamorphosis may therefore not be constrained by escape performance. In contrast, low performance of late stage embryos may limit the age at which hatching occurs in this species. Supported by NSF IBN 9875245.