Meeting Abstract

6.10  Wednesday, Jan. 4  Contractile Properties and Myosin Expression in Swimming and Feeding Muscles of Centrarchid Fishes COUGHLIN, D. J.*; MISTRY, H.; CAMPION, L. A.; CHOI, S.; Widener Univ.; Widener Univ.; Widener Univ.; Widener Univ.

In centrarchid fishes, such as bluegill and largemouth bass, the contractile properties of feeding and swimming muscles show different scaling patterns. While the maximum shortening velocity (Vmax) and rate of relaxation from tetanus of swimming or myotomal muscle slows with growth, the feeding muscle show distinct scaling patterns. Epaxial muscle, which is used to elevate the head during feeding strikes, retains fast contractile properties across a range of fish sizes in both species. In bass, the sternohyoideous muscle, which depresses the floor of the mouth during feeding strikes, shows faster contractile properties with growth. The objective of this study was to determine the molecular basis of these different scaling patterns. We examined the expression of two muscle proteins, myosin heavy chain (MyHC) and parvalbumin (PV), that affect contractile properties. We hypothesized that the relative contribution of slow and fast MyHC isoforms will modulate Vmax in these fishes, while the presence of PV in muscle will enhance rates of muscle relaxation. Myotomal muscle displays an increase in slow MyHC expression with growth, in agreement with its physiological properties. Feeding muscles such as epaxial and sternohyoideus show no change or a decrease in slow MyHC expression with growth, again as predicted from ontractile properties. PV expression in myotomal muscle decreases with growth in both species, as has been seen in other fishes. The feeding muscles again show no change or an increase in PV expression with growth, contributing to faster contractile properties in these fishes. Both MyHC and PV appear to play important roles in modulating muscle contractile properties of swimming and feeing muscles in centrarchid fishes.