CHANGES OF ULTRASTRUCTURE AND CYTOCHEMICAL MG2-ATPASE ACTIVITY IN ORDINARY MUSCLE OF CULTURED AND WILD RED-SEA BREAM DURING STORAGE IN ICE()

We made a comparative study on changes of ultrastructure and cytochemi cal Mg2+-adenosine triphosphatase (Mg2+-ATPase) in ordinary muscle of cultured and wild red sea bream during storage in ice. Degeneration of the Z lines of ordinary muscle was faster in cultured fish than in wi ld fish. In cultured fish, the structure of the Z lines became discont inuous within 1 day in ice. While, the Z lines showed continuity until day 3 in wild fish. Degenerations of other organella, such as the sar coplasmic reticulum, mitochondria, A band, and I band were similar in both cultured and wild fish. Mg2+-ATPase activity was found at the sar coplasmic reticulum, near both ends of A band, mitochondria, and nucle ar membrane in both fish immediatedly after death. Mg2+-ATPase activit y in these organella became undetectable on day 5 in cultured fish, bu t it was still weakly detected on day 7 in wild fish. These results su ggested that ultrastructure and cytochemical Mg2+-ATPase activity are good indicators for post-mortem changes in fish muscle.