Meeting Abstract
P2.36 Saturday, Jan. 5 DIFFERENTIAL THERMAL TOLERANCE AND ENERGETIC TRAJECTORIES DURING ONTOGENY IN PORCELAIN CRABS, GENUS PETROLISTHES MILLER, N.A.*; PAGANINI, A.W.; STILLMAN, J.H.; San Francisco State University; San Francisco State University; San Francisco State University and Univ. of California, Berkeley namiller@sfsu.edu
Thermal tolerance limits of marine intertidal organisms are elevated compared to subtidal species, but are typically only slightly higher than maximal habitat temperatures. The small thermal safety margins maintained by intertidal organisms suggest high thermal tolerance is associated with a physiological cost. If true, we hypothesize that species that transition between intertidal and planktonic thermal habitats during ontogeny, will adjust their thermal tolerance accordingly, to capitalize upon potential energy savings while in a thermally benign habitat. We tested this hypothesis in two porcelain crab species (genus Petrolisthes) that transition between the thermally stressful, intertidal zone as embryos, to the thermally benign pelagic zone as larvae, and back at settlement. We found the more thermally tolerant mid-intertidal species, Petrolisthes cinctipes, reduced thermal tolerance as a pelagic larvae, but that this was not associated with a reduced larval metabolic rate. The less thermally tolerant subtidal species, Petrolisthes manimacilis, reduced thermal tolerance throughout ontogeny with the lowest thermal limits in juveniles, though reduced thermal tolerance was not reflected in a reduced metabolic rate. While embryos and juveniles of P. cinctipes had thermal tolerance limits near habitat thermal maxima (~32.5 °C), all three life-history stages in P. manimaculis (especially embryos and larvae) exhibited considerable thermal safety margins. The mechanisms underlying this “excess” thermal tolerance in P. manimacilis embryos (~5 °C higher than the adults whose abdomen they are brooded upon) is unknown, but suggests that patterns of thermal tolerance in early life history stages are species specific.
