Seasonality of Critical Thermal Maximum (CTmax) in the Asian Shore Crab (Hemigrapsus sanguineus)

Abstract

The invasive Asian shore crab (Hemigrapsus sanguineus) has had a major impact on the ecology of the rocky intertidal habitat of the northeastern North American coast by outcompeting native and resident crab species, yet its thermal biology has not been studied. In a warming climate, an examination of the thermal tolerance limits of such a major invasive species is warranted. Critical thermal maximum (CTmax) was determined by finding the temperature at which an individual loses its ability to right itself within one minute (loss of righting response, LRR). Significant seasonal differences were identified in the critical CTmax of H. sanguineus. The summer season mean CTmax was found to be 37.2 °C, while the winter season mean was found to be 33.1 °C. A negative trend was also identified between carapace width and CTmax within the warm and cold seasons, though the cold season trend was only evident when individuals with a carapace width greater than 20 mm were excluded. Contingent on further study, these findings indicate a potential factor in H. sanguineus' decline since 2001.