Fig. 4. Influence of temperature on the ultrastructure of myotomal muscle in larval Atlantic herring (Clupea harengus) (Vieira and Johnston, 1992). (A) Camera lucida drawing of a 1-day old larva sectioned immediately posterior to the yolk-sac. (B) Transverse electron micrograph of a 1-day old herring larva reared at 12°C. Abbreviations: ds, dermal scale; g, gut; im, embryonic fast muscle fibre; mc, mucocyte; ms, undifferentiated myoblast; mt, mitochondria; my, myofibril; n, myonucleus; nt, notochord; pn, pronephros; SC, spinal cord; sk, skin; sm, embryonic slow muscle fibre. (C,D) The volume density of mitochondria (% fibre volume) in (C) embryonic slow and (D) embryonic fast muscle of 1-day old larvae reared at 5, 10 or 15°C until hatching. Values represent means ± s.e.m., N=20 fibres from 5 larvae per temperature.