Fig. 3. Phases of growth observed in the myotomal muscle of Antarctic and sub-Antarctic notothenioid fish that have a relatively low final muscle fibre number. (A) Transverse section through the trunk stained with Haematoxylin–Eosin from an adult icefish Chaenocephalus aceratus, 27.6 cm standard length (SL). Note the relatively uniform distribution of large diameter (approx. 200 µm) muscle fibres. (B) Transverse section of a region of fast muscle fibres from an adult Notothenia coriiceps, 35.5 cm SL, stained with Scarab Red to visualise collagen fibrils. The arrowheads show the apparent splitting of a fibre into smaller daughter fibres each surrounded by a connective tissue sheath. (C) Transverse section of a region of fast muscle fibres from an adult Patagonotothen longipes sp. (27.8 cm SL) showing the apparent splitting of a fibre into smaller daughter fibres. Arrowheads indicate the position of myonuclei. ms, myosepta. Scale bars, 200 µm (A,B); 100 µm (C).