Meeting Abstract
For sessile invertebrates, temperature fluctuations are unavoidable and often deleterious, causing reduced performance or survival. While there are many studies on heat stress in invertebrates, less is known about the effects of cold, especially on a cellular level. The invasive zebra mussel can serve as a model species for investigating the physiological response to long-term cold temperatures. A previous experiment showed phosphorylated AMP-activated protein kinase (pAMPK) levels increased with acute cold exposure. Given that pAMPK levels indicate metabolic stress and energy imbalances, data suggest mussels have increased energy demands in cold water, which seems unexpected for an ectotherm. One explanation is the process of seasonal acclimation is energetically taxing. Alternatively, cold exposure may cause cellular damage, increasing the energy needed for maintenance or repair. To investigate this response, mussels were either acclimated to 10° C for two weeks and held at 10° C for an additional four weeks or maintained at 26° C for six weeks. Mussel mortality, shell and soft tissue growth, hemolymph concentration, total antioxidant capacity, and the levels of heat shock protein 70 (HSP70), HSP22, total AMPK, and pAMPK were measured. Results show that total antioxidant capacity, hemolymph concentration, and shell growth did not vary between treatments. However, mussels in the 10° C treatment gained tissue mass while those at 26° C lost tissue. pAMPK, total AMPK, and HSP22 levels were significantly elevated in mussels held at 10° C, but the same was not seen for HSP70 levels. Overall, data do not suggest that 10° C is leading to substantial cellular damage, but rather these increased energy demands may be associated with the cellular changes associated with seasonal acclimation.
