BERNATIS, J.L.*; MCGAW, I.J.; University of Florida; University of Nevada Las Vegas: Behavioral Modifications of the Dungeness Crab During Feeding and Digestion in Hypoxia

The Dungeness crab, Cancer magister, inhabits areas that are frequently subjected to hypoxic episodes. This species has physiological mechanisms that allow it to cope with acute periods of hypoxia, nevertheless, these may be compromised during feeding and subsequent digestion. The present study investigated the behavior of Cancer magister during feeding and digestion in hypoxia. Crabs were exposed to a range of oxygen concentrations (21 kPa � 1.5 kPa) and prey manipulation was monitored. All crabs fed in oxygen concentrations ≥ 10.5 kPa. Crabs exposed to oxygen concentrations below 3.2 kPa consumed significantly less food. Following feeding, the animals held onto the food, tucking it under their thorax but did not resume feeding. Crabs that did not feed in the lower oxygen concentrations (<3.2kPa), started to feed when oxygen concentrations were raised to 5.8 kPa. A high (20.5 kPa � 10.5 kPa) and low oxygen gradient apparatus (10.5 kPa � 2.8 kPa) was used to examine oxygen preference behavior of starved and postprandial crabs. While there was no preference in the high gradient, in the low oxygen gradient both postprandial and starved crabs preferred oxygen concentrations ≥ 5.2 kPa. A distinct difference in behavior was observed between starved and postprandial crabs in the low gradient. All postprandial crabs attempted to break the water/air surface to gain additional oxygen, while no starved crabs demonstrated this behavior. The habitat of C. magister is in a constant state of flux, varying from normoxic to anoxic over small spatial scales. This study suggests crabs may use external oxygen receptors that allow rapid behavioral modification in a fluctuating environment. Thus the nutritional state of the animal is important in behavioral reactions and may influence the distribution of crabs in their natural environment