Meeting Abstract

139.3  Monday, Jan. 7  Differential physiological tolerance to low salinity exposure in two color morphs of the green crab, Carcinus maenas PENNOYER, K.E.*; FREDERICH, M; Univeristy of New England, Biddeford, ME and Texas A and M University Corpus Christi, TX; Univeristy of New England, Biddeford, ME kpennoyer@une.edu

The European green crab, Carcinus maenas, is variable in ventral carapace coloration. Crabs are green after molting and become dark red after prolonged intermolt. Previous studies have shown that red morphs are weaker osmoregulators and have poorer tolerance to low salinity exposure than green morphs. Cellular data to complement this organismic response is lacking. We exposed crabs to 10ppt seawater to assess hemolymph osmolarity, oxygen consumption, righting response and treadmill running endurance. Changes in mRNA expression were assessed for ion transporters (carbonic anhydrase, Na⁺/K⁺-ATPase, Na⁺ -K⁺-2Cl^–-cotransporter, and Na⁺/H⁺ antiporter), stress marker (HSP70) and indicators of cellular energy status (AMPK, arginine kinase). At 10ppt red morphs exhibited lower hemolymph osmolarity and poorer whole animal performance. Concurrently, greens morphs exhibit a greater upregulation of genes responsible for ion regulation, cellular stress response and cellular energy status. Whereas red morphs crabs show minimal if any upregulation in these genes. To test the hypothesis that the red morphs reached a physiological limit of ion regulation at 10ppt, suggested by higher morality, green morphs were exposed to 10ppt and red morphs to 12ppt, resulting in a similar hemolymph osmolarities of 750 mOsm in both morphs. After matching the hemolymph osmolarity both morphs showed similar mRNA upregulation. Therefore, the two color morphs seem to have different ion regulatory capacities and reach a critical point of no longer being able to upregulate the respective transporters at different salinities. Funded by NSF IOB0640478 and DGE0841361.