Effects of low temperature exposure and acclimation on the behavioural responses of the green crab (Carcinus maenas) from Newfoundland, Canada.

Abstract

European green crab (Carcinus maenas) are a highly successful invasive species of intertidal crustacean. The northern most limit of their invasive range on the east coast of North America is the island of Newfoundland (NL), Canada, where they can experience water temperatures as low as -1 °C during the winter. Green crabs' ability to tolerate a large temperate range is one of the most important characteristics responsible for their invasive success. We investigated the behavioural responses of the green crab to a temperature reduction regime, and long-term acclimation to winter (2 °C) and summer (12 °C) water temperatures in NL. Locomotor activity declined as temperature decreased with a concomitant increase in time spent buried, showing a marked change in these parameters at approximately 4 °C. There was also a marked reduction in activity after long-term exposure to cold temperatures (2 °C) compared to controls (12 °C). However, locomotor activity did not cease completely, even after long-term exposure to 2 °C, indicating that crabs remained responsive to their environment. Crabs took longer to respond to food items and consumed less food after long-term acclimation to 2 °C, compared to 12 °C; however feeding did not cease completely. Collectively, these responses suggest that the green crab enters a dormant state below 5 °C, rather than true torpor, in which they continue to move and feed, albeit more slowly and at lower rates. The green crab population in NL is a genetically hybridized population with both southern and cold-resistant northern haplotypes, however, they react in a similar way to most other populations across their native and invasive range and so the observed behavior may be an inherent reaction to cold.