Regional variations in fibre growth dynamics of myotomal and caudal fin muscles in relation to body size of a freshwater teleost, Barbus sarana (Cuv. & Val.).

ABSTRACT

The growth of red fibres in anterior and middle myotomal regions of B. sarana was mainly by hyperplasia in smaller size classes. In higher size classes, growth by hyperplasia was greater in posterior myotomal region compared to the other two myotomal regions. The growth of pink fibres in anterior myotomal regions was mainly by hypertrophy. The middle and posterior myotomal regions showed fibre growth by hyperplasia. The growth dynamics of white fibres revealed more or less similar pattern in all three myotomal regions against the somatic development. White fibres grew by hyperplasia up to 8 cm F.L. size classes and thereafter by hypertrophy. However, in > 12 cm F.L. size classes, the mean diameter of white fibres did not increase significantly. Similar pattern of growth was found in the white fibres of caudal fin muscle. It is interesting to note that the hyperplasia was mostly completed in the white fibres of the smallest fish studies, whereas, it continued to quite larger fish size in red and pink fibres. Thus, hyperplasia and hypertrophy may be responsible for growth in all fibre types in all myotomal regions in relation to somatic development in this small and medium growing species.