Muscle fibre types and distribution in sub-Antarctic notothenioids.

DANIEL ALFREDO FERNANDEZ; JORGE CALVO,; CRAIG FRANKLIN,; ALISTAIR JOHNSTON, IAN

JOURNAL OF FISH BIOLOGY

Año: 2000 vol. 56 p. 1295 - 1311

0022-1112

The presumptive tonic muscles fibres of Cottoperca gobio, Champsocephalus esox, Harpagiferbispinis, Eleginops maclovinus, Patagontothen tessellata, P. cornucola and Paranototheniamagellanica stained weakly or were unstained for glycogen, lipid, succinic dehydrogenase(SDHase) and myosin ATPase (mATPase) activity. Slow, intermediate and fast twitch musclefibres, distinguished on the basis of the pH stability of their mATPases, showed intense,moderate and low staining activity for SDHase, respectively. Slow fibres were the majorcomponent of the pectoral fin adductor profundis muscle. The proportion of different musclefibre types varied from the proximal to distal end of the muscle, but showed relatively littlevariation between species. The myotomes contained a lateral superficial strip of red musclecomposed of presumptive tonic, slow twitch and intermediate fibres, thickening to a majorwedge at the horizontal septum. All species also had characteristic secondary dorsal andventral wedges of red muscle. The relative abundance and localization of muscle fibre typesin the red muscle varied between species and with body size in the protandric hermaphroditeE. maclovinus. The frequency distribution of diameters for fast twitch muscle fibres, the majorcomponent of deep white muscle, was determined in fish of a range of body sizes. The absenceof fibres <20 m diameter was used as a criterion for the cessation of muscle fibre recruitment.Fibre recruitment had stopped in P. tessellata of 13·8 cm LT and E. maclovinus of 32·8 cm LT,equivalent to 49 and 36·5% of their recorded maximum sizes respectively. As a result in 20-cmP. tessellata, the maximum fibre diameter was 300 m and 36% of fibres were in excess of200 m. The unusually large maximum fibre diameter, the general arrangement of the redmuscle layer and the extreme pH lability of the mATPase of fast twitch fibres are all commoncharacters of the sub-Antarctic and Antarctic Notothenioids, including Cottoperca gobio, thesuggested sister group to the Notothenidae.