Thesis

Impacts of density and species interactions on the reproductive physiology of porcelain crab species Petrolisthes cinctipes and Petrolisthes manimaculis

Species redistribution is a well-documented response to global change. Understanding the resulting physiological responses of organisms is critical for predicting community composition changes that may occur under future conditions. The porcelain crab Petrolisthes cinctipes resides in the upper to mid intertidal zone and is expected to behaviorally respond to rising temperatures by shifting its distribution lower in the intertidal zone where they will experience higher densities and likely interact more often with a congeneric competitor, Petrolisthes manimaculis. In this study, I addressed how increased density and inter- and intra- species interaction impacts injury, heat shock protein (hsp) expression and reproduction, indexed by circulating levels of the yolk protein vitellogenin (Vg) and expression. To address these questions, female crabs were randomly exposed to high density (787 crabs/m2) or low-density (250 crabs/m2) treatments with and without the presence of a competitor species for 14 days. We found that density and species interactions did not affect injury but significant hsp and Vg differences were detected in P. manimaculis. Furthermore, Vg protein and expression results show species sensitivity along a lunar cycle axis suggesting reproductive state during the New Moon may result in heightened sensitivity to stress. These results highlight the importance of species interactions and environmental cues under changing environmental conditions and further our understanding of how thermally transduced stress can impact animal populations through physiological stress.

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