Skeletal muscles constitute the main part of fish body. It has unique structure that adapts its function in the aquatic environment. The main objective of the present study is to make correlations between the histological and ultrastructure features of seabass (L. calcarifer), the musculature to fish growth and the development. Fish were obtained from (Fish Farming Center, Ministry of Agriculture, Jeddah). Specimens were divided into 5 groups according to their weight. Fish were anaesthetized by clove oil and the distribution of various types of fibers (red and white) was determined. The muscle weight and length were recorded. Parts of the muscle were prepared for transmission electron microscopy examination. The results showed that there was a positive significant correlation between body and muscle length and weight. Histological study showed that fish growth was due to increase in both muscle fiber density and area. Connective tissue of fish musculature was found to be consisted mainly of reticular fibers scanty collagen fibers were seen in myosepta separating myotomes. Myofiber hypertrophy was associated with shortening of peripheral ribbon shaped myofibrils and addition of central polygonal ones. An increase of intermyofibril sarcoplasm was also observed. Seabass fish growth could be attributed to both hypertrophy and hyperplasia of skeletal myofibers.
Key words: Asian Seabass - red fibers - White fibers - myofiber hypertrophy- myofiber hyperplasia
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