Meeting Abstract
85.1 Sunday, Jan. 6 Thermal Acclimation in Rainbow Smelt, Osmerus mordax, Leads to Faster Myotomal Muscle Contractile Properties and improved swimming performance. COUGHLIN, DJ*; WOYTANOWSKI, JR; Widener Univ.; Widener Univ. djcoughlin@widener.edu
Rainbow smelt (Osmerus mordax) display an impressive ability to acclimate to very cold water temperatures. These fish express both anti-freeze proteins and glycerol in their plasma, liver, muscle and other tissues to avoid freezing at sub-zero temperatures. Maintenance of glycerol levels requires active feeding in very cold water. To understand how these fish can maintain activity at cold temperatures, we explored thermal acclimation by the myotome of smelt exposed to cold water. We hypothesized that cold-acclimated fish would show enhanced swimming ability due to shifts in muscle contractile properties. We also predicted that shifts in swimming performance would be associated with changes in the expression patterns of muscle proteins such as parvalbumin (PV) and myosin heavy chain (MyHC). Swimming studies show significantly faster swimming by smelt acclimated to 5oC compared to fish acclimated to 20oC. The cold-acclimated fish also had faster muscle contractile properties, such as a maximum shortening velocity (Vmax) almost double that of warm-acclimated fish. Cold-acclimation is associated with a modest increase in PV levels in the swimming muscle. More significantly, fluorescence microscopy using anti-MyHC antibodies indicates that MyHC expression in the myotomal muscle shifts in response to exposure to cold water. The complex set of physiological responses that comprise cold-acclimation in smelt includes modifications in muscle function to permit active locomotion in cold.
