The effects of temperature on walking and righting in temperate and Antarctic crustaceans

Antarctic marine invertebrates live in a cold, thermally stable environment and cannot tolerate large changes in body temperature (i.e. they are stenothermal). Their temperate relatives, by contrast, are eurythermal, living in warmer and thermally more variable environments. Have these different environments influenced how specific behaviours are affected by changes of temperature? This question was addressed in two temperate crustaceans, the decapod Carcinus maenas and isopod Ligia oceanica, and two Antarctic crustaceans, the isopod Glyptonotus antarcticus and amphipod Paraceradocus gibber. The thermal dependence of walking speed was analysed by contrasting the slopes of the linear part of each species' behavioural curve. Over the temperature ranges analysed, the temperature sensitivity of walking speed in the stenotherms was 13-23% that of the eurytherms when measured in body lengths s(-1). There was a linear relationship between walking speed and temperature up to +4.5 degrees C in the Antarctic species G. antarcticus and P. gibber. Elevating temperature by up to 3.5 degrees C above the maximum temperature experienced in the Antarctic (+1 degrees C), does not lead to an acute breakdown of motor coordination. We describe for the first time the righting behaviour of G. antarcticus. The mean time-to-right tended to a minimum on warming from -2 to+5 degrees C, but this trend was not statistically significant. Our results suggest that the physiological adaptations which permit continued activity at low Antarctic temperatures have resulted in a lower thermal dependence of activity in Antarctic species, compared to related temperate species