Muscle cellularity, enzyme activities, and nucleic acid content in meagre (Argyrosomus regius)

Abstract

Anatomical and biochemical indices of axial muscle growth were monitored in farmed meagre ( Argyrosomus regius (Asso, 1801)), a species with larger ultimate size. Within the first 19 months of a production cycle, body mass exceeded 1300 g. The specific daily growth rate ranged from a winter low of 0.2% to a summer high of 1.3%. Axial muscle RNA:DNA ratio decreased and cytochrome c oxidase levels increased from spring to winter, indicating a metabolic reorganisation of this tissue in response to winter temperature lows. Body mass correlated positively with increased lactate dehydrogenase activity and myofibre size (hypertrophy). The DNA:protein ratio, the myofibre density, and the percentage of small myofibres (0–150 µm2) decreased towards the end of the production cycle. However, small myofibres persisted even after the first 20 months of rearing. Compared with commonly cultivated species in the Mediterranean region, meagre exhibits delayed onset of puberty, larger ultimate size, and growth rate that is supported by the recruitment of new muscle fibres. This is in agreement with the hypothesis of a relationship between ultimate size and muscle growth dynamics.