15.6 Wednesday, Jan. 4 Performance in the Atlantic blue crab: Effects of anemia and hypoxia BURNETT, L.*; DANIELSON, M.; MCELROY, E.; STOVER, K.; BURNETT, K.; College of Charleston; College of Charleston; College of Charleston; College of Charleston; College of Charleston BurnettL@cofc.edu
The concentration of the respiratory pigment hemocyanin (Hc) in Callinectes sapidus can be quite variable and can depend on such factors as molting and oxygen levels in water. We tested the effects of anemia (crabs with Hc concentration < 3 g Hc/100 mL) on the ability of male crabs to walk on an underwater treadmill while assessing fatigue after each hour of walking. Treadmill speed was set at 8 m/min and water was either well-aerated or made hypoxic (4 kPa O2). Fatigue was assessed using a “pull test” that measured the force crabs used to hold on to and then release a stationary mesh stage when pulled away, mimicking the way a male crab holds a female during mate guarding. Anemic crabs had a mean Hc concentration of 2.52 g/100 mL (N=8 ±0.05 SEM), while controls had 6.33 g/100 mL (N=7 ±0.7). Both anemic and control crabs were able to complete 4 hours of walking on the treadmill. Force generated by anemic crabs on the “pull test” decreased dramatically over 4 hours of walking to only 53% of the initial value tested before walking. This is in contrast to control crabs which showed no significant fatigue after 4 hours. In separate experiments, crabs made artificially anemic by removing hemolymph and replacing it with sterile saline (mean=1.92 g Hc/100 mL) revealed the same pattern as naturally anemic crabs. Non-anemic crabs with “control” levels of Hc were also exposed to hypoxia (O2=4 kPa) during walking and were unable to walk more than 2 hours. “Pull test” measures after 2 h were 47% of the initial. Mean hemolymph lactate after 4 hours was 3.9 mmol/L in controls and 4.4 in anemic crabs; these were significantly different (P<0.001) from 18.7 in hypoxic crabs after only two hours. (NSF DBI-1062990, IOS-0725245).