Fig. 2. Phases of growth observed in the myotomal muscle of Antarctic and sub-Antarctic notothenioid fish. (A–G) Transverse sections through the trunk stained with Haematoxylin–Eosin (A) Section from Notothenia coriiceps, 11.2 cm standard length (SL), stained with the antibody S58, showing the presence of a superficial layer of slow muscle fibres (arrows) dorsal to the major horizontal septum. (B) Trematomus newnesi, 13.3 cm SL, section stained with S58 showing the slow muscle fibres adjacent to the lateral line nerve (arrows). The fast muscle fibres were counterstained with Haematoxylin–Eosin. (C) Dorsal region of the trunk in a juvenile Notothenia coriiceps, 6.0 cm SL. The arrowheads indicate zones of stratified hyperplasia containing fibres of smaller diameter than the surrounding tissue. (D) The start of mosaic hyperplasia (arrowheads) in the fast muscle of a juvenile Notothenia coriiceps, 6.7 cm SL. Note that small diameter satellite fibres are not uniformly distributed through the field of view. (E) The pattern of fibre diameters characteristic of mosaic hyperplasia was still present in E. maclovinus of 37.5 cm SL. (F) Active mosaic hyperplasia (arrowheads) in the fast muscle of a juvenile Eleginops maclovinus, 4.7 cm SL. (G) The smallest specimen of Paranotothenia magellanica captured, 9.3 cm SL, showed a mosaic pattern of fibre diameters (arrowheads). s, slow muscle; f, fast muscle; sk, skin; ms, myosepta. Scale bars, 200 µm (A–C,E); 100 µm (D,F,G).