CURTIS, D.L.**; MCGAW, I.J.; University of Nevada, Las Vegas and Bamfield Marine Sciences Centre; University of Nevada, Las Vegas and Bamfield Marine Sciences Centre: Feeding and digestion in response to low salinity in the Dungeness crab, Cancer magister

The Dungeness crab, Cancer magister, is classified as a weak osmoregulator. Nevertheless, this species often forages in estuaries where it may encounter episodes of low salinity. We hypothesized that the energy required for osmoregulation in estuarine conditions may limit that available for feeding and digestion. In the present study, changes in the feeding behaviour of crabs exposed to decreased salinity were examined as a function of acclimation time and starvation time. The likelihood of feeding decreased with salinity, but increased with starvation time, suggesting a trade-off between starvation time and osmoregulation when feeding in low salinity conditions. In 50% seawater, the number of crabs feeding increased with acclimation time. Crabs did not feed in salinities below 30% seawater. Changes in digestive processes were examined by following the passage of a radio opaque meal through the gut system with a fluoroscope. Exposure to low salinity following feeding resulted in a decreased rate of foregut contraction, leading to an overall increase in gastric evacuation time. The results of this study suggest that there is a prioritization during low salinity exposure, whereby osmoregulatory processes may limit the amount of energy available for feeding and digestion.