Histological analysis of fibres in myotomes of antarctic fish. II. Morphometry of muscle fibres and capillaries.

In a survey of nine species of antarctic Teleosts belonging to the families Chaenichthyidae (two species) and Nototheniidae (seven species) the surface density (Sv), volume density (Vv), number of muscle fibres and capillaries in 0.1 mm2 area and the diameters of capillaries were estimated. Muscle fibre to capillary ratio (C:F) and streamlinedness (1/h) of the fish were also calculated. It was found that the Sv values of the muscle fibres are inversely correlated with streamlinedness of the fish. However, this relation is disturbed in these fish which have low metabolic activity. In the genera Notothenia and Dissostichus only the Sv of the muscle fibres is greater in the caudal myotomes in comparison with those in the trunk. The capillarization of the muscle tissue in white-and red-blooded fish does not differ significantly, it differs however, in the case of musculus lateralis magnus (MLM) and musculus rectus lateralis (MRL). Capillary to fibre ratio (C:F) significantly differs between red and white portion of muscle in all species investigated. The diameters of white-blooded fish capillaries are importantly greater in comparison with those of red-blooded fish. It is concluded that muscles of white-blooded fish are morphologically adapted to the lack of hemoglobin and myoglobin by: relatively large diameters of their capillaries, but not by their density, and by the low Sv values of their muscle fibres.