Suitability of measured parameters and minimum sample sizes required to quantify capillary supply to fish muscle
Abstract
In the myotomal muscle of fish, metabolic fibre types are arranged in discrete layers. There is considerable variation in the capillary supply both to fast and slow muscle, and between homologous muscles of different species. Mitochondrial volume densities, VV(mt,f), in fish slow muscle (0.2 to 0.4) are similar to those found for mammalian heart and are positively correlated with the number of capillaries/mm2 of muscle fibre. VV(mt,f) for fast fibres varies from 0.001 to 0.09. This paper examines the relative merits of different indices of capillary supply to fish muscle, and determines the minimum sample numbers required for reproducible estimates. A minimum sample size of up to 500 fibres was required to estimate capillary density, NA(c,f), for conger slow and fast muscle. These values may be substantially reduced in species with a higher capillary density. Estimation of capillary surface SV(c,f), and volume densities, VV(c,f), may provide a better estimate of the potential capillary gas exchange. However, these indices require a better understanding of the 3-Dimensional structure of the capillary bed.