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Anuran metamorphosis is an extreme transformation from tadpole to frog that involves tremendous morphological and behavioral change. During this transition (Gosner stages 42-46), metamorphs are exposed to both aquatic and terrestrial selective pressures (e.g., predators, desiccation). Their behavior may be crucial for survival, but it is not well studied. Our goal was to describe morphological and behavioral patterns during metamorphosis in red-eyed treefrogs, Agalychnis callidryas. We first quantified development through metamorphosis by measuring and staging 25 wild-caught individuals every 8 h. We then conducted field behavioral observations of 37 metamorphs, at various developmental stages, that had emerged from a pond in Gamboa, Panama. Emerging metamorphs crawled rapidly out of the pond, usually during Gosner stage 43, and then remained relatively inactive. Tail absorption was non-linear; 80% of the tail absorbed in ~24 h while the remainder took 4 days. After tail fin absorption, frogs moved away from the pond and upwards in the vegetation. The most commonly observed postures were sitting alert and water conserving, but metamorphs also exhibited less common behaviors including back flexing, limb stretching, reaching, and head bobbing. We also surveyed diel timing of emergence from a mesocosm experiment, in which tadpoles were reared in 400 L tanks either with no predators, a giant water bug, or a fishing spider. Few metamorphs emerged during daylight; most (>60%) emerged after dusk, by 9pm. There was some indication of later emergence from spider tanks suggesting behavioral plasticity during metamorphosis could improve survival during this vulnerable life stage.
Abstract from conference program at http://www.sicb.org/meetings/2011/schedule/abstractdetails.php3?id=701.
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VCU Biology Presentations