Tectal CRFR1 receptor involvement in avoidance and approach behaviors in the South African clawed frog, Xenopus laevis

Current State of Conservation Physiology for Amphibians: Major Research Topics and Physiological Parameters

Analysis of physiological responses can be used to assess population health, identify threat factors, and understand mechanisms of stress. In addition to this, conservation physiologists have sought to establish potential management strategies for environmental change and evaluate the effectiveness of conservation efforts. From past to present, the field of conservation physiology is developing in an increasingly broader context. In this review, we aim to categorize the topics covered in conservation physiology research on amphibians and present the measured physiological parameters to provide directions for future research on conservation physiology. Physiological responses of amphibians to environmental stressors are the most studied topic, but conservation physiological studies on metamorphosis, habitat loss and fragmentation, climate change, and conservation methods are relatively lacking. A number of physiological indices have been extracted to study amphibian conservation physiology, and the indices have varying strengths of correlation with each subject. Future research directions are suggested to develop a comprehensive monitoring method for amphibians, identify interactions among various stressors, establish physiological mechanisms for environmental factors, and quantify the effects of conservation activities on amphibian physiology.

Sub-chronic administration of fluoxetine does not alter prey-capture or predator avoidance behaviors in adult South African clawed frogs (Xenopus laevis)

Animals will halt foraging efforts and engage defensive behaviors in response to predator cues. Some researchers have proposed that the switch from appetitive to avoidance behavior resembles anxiety, but most work on this has been performed in a limited number of animal models, primarily zebrafish and rodents. We used adult South African clawed frogs (Xenopus laevis) to determine if the canonical anxiolytic fluoxetine alters predator-induced changes in appetitive and avoidance behavior in a laboratory-based trade-off task that mimics foraging/predator avoidance tradeoffs in the wild. We hypothesized that sub-chronic fluoxetine treatment (20 d) would not affect baseline behavior but would reverse predator-induced changes in food intake, appetitive and avoidance behavior, and the abundance of anxiety related gene transcripts in the optic tectum, a brain area central to ecological decision making in frogs. We found that fluoxetine significantly reduced baseline locomotion compared to vehicle-treated animals. Fluoxetine had no effect on appetitive and avoidance behaviors that were sensitive to predator cues in this assay and did not alter any of the anxiety-related transcripts in the tectum. We conclude that while peripheral sub-chronic administration of fluoxetine significantly reduces locomotion, it does not modify predator-induced changes in approach and avoidance behaviors in this assay. Our findings are not consistent with visual predator cues causing state anxiety in adult frogs.