Thesis

Variation in thermoregulation and linking whole organism behavior to thermosensory neurophysiology in the porcelain crab, Petrolisthes cinctipes

Small-scale shifts in species distributions are expected to occur under future climate for many species. These shifts can have consequences as they alter population dynamics, and it is important to understand when and why they occur. The intertidal porcelain crab Petrolisthes cinctipes currently experiences temperatures that can reach near-lethal levels at low tide. However, the thermal thresholds that trigger migration to cooler microhabitats and the extent to which crabs move in response to temperature remain unknown. We tested for effects of body size and reproductive state on escape temperature (T e s c ) . In addition, we tested for the relationship between T eSc and the temperature of peak action potential firing frequency in nerve fibers. We found that both size and reproductive state influence behavioral sensitivity to temperature. Small crabs tolerate significantly higher temperatures before they move to cool refuges (a higher T eSc ) compared to large crabs. In addition, non-gravid crabs have significantly higher T eSc than gravid females. Tesc is positively correlated with peak neural performance of spontaneous action potentials. The vulnerability of marine organisms to global change is predicated by their ability to utilize and integrate physiological and behavioral strategies as a response to temperature, in order to maximize survival and reproductive fitness; understanding these strategies will allow predictions of species distributions under warming.

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