Meeting Abstract

P2.81  Tuesday, Jan. 5  Distribution of nuclei in white muscle fibers of juvenile and adult black sea bass, Centropristis striata PRIESTER, C.*; MORTON, L.C.; KINSEY, S.T.; WATANABE, W.O.; DILLAMAN, R.M.; UNC Wilmington cpl3791@uncw.edu

Studies in our lab on white muscle fibers from blue crab and black sea bass, have demonstrated how diffusion limitations can influence organelle distribution. Here we investigated the distribution of nuclei at equivalent sites in juvenile and adult black sea bass ranging from 0.4g to 4840g. In large fish, samples were also compared at 6 sites along their length. Nuclei were counted in 1µm optical sections using confocal microscopy of DAPI-stained muscle fibers. As C. striata increased in body size, mean muscle cell diameter increased from 36μm in the 0.4g fish to 216 μm in the 1885g fish. Growth beyond 2000g triggered the recruitment of new, smaller fibers (<120µm), creating a nearly bimodal distribution in fish from 2691g to 4840g. Mean fiber diameters in large fish (2258g-4840g) sampled frontal to caudal did not differ at any location, but, the most caudal region had a smaller range and coefficient of variation, and did not have very small or very large fibers. Nuclei in the smaller fibers were only subsarcolemmal (SS), whereas in larger fibers, nuclei were more numerous and included intermyofibrilar (IM) nuclei. The IM nuclei of large C. striata were not as evenly distributed nor as numerous as in the blue crab. They were either randomly distributed, or arranged in a ring pattern. This ring pattern of nuclei was only in large (>2000g) fish, and predominantly in the middle three sample regions of the fish, not in the caudal or frontal regions. Such a pattern may be the result of SS nuclei being uniformly released from the sarcolemma due to some unknown episodic event that only affected a portion of the fibers. In addition, examination of fiber diameters of age-matched versus size-matched fish indicated that mass, not age, determines fiber diameter.