| Summary: | Chapter 1. A general introduction into the adaptation of teleost fish to changing thermal environments. The underlying mechanisms at all levels of organization are reviewed in relation to adaptive change over evolutionary and seasonal time-scales. Chapter 2. 1. The contractile properties of swimming muscles have been investigated in marine teleosts from Antarctic (Trematomus lepidorhinus, Pseudochaenichthys georgianus), temperate (Pollachius virens. Limanda limanda. Agonis cataphractus. Callionymus lyra) and tropical (Abudefduf abdominalis, Thalassoma duperrevi) latitudes. 2. Small bundles of fast twitch fibres were isolated from anterior myotomes and/or the pectoral fin adductor profundis muscle (m.add.p). Live fibre preparations were viable for several days at in vivo temperatures, but became progressively inexcitable at higher or lower temperatures. The stimulation frequency required to produce fused isometric tetani increased from 50Hz in Antarctic species at 0°C to around 400 Hz in tropical species at 25°C. Maximum isometric tension (P0) was produced at the normal body temperature (NBT) of each species (Antarctic, 0-2°C; North Sea and Atlantic, 8-10°C; Indo-West Pacific, 23-25°C). P0 values at physiological temperatures (200-300 kN m-2) were similar for Antarctic, temperate and tropical species. 3. A temperature induced "tension hysteresis" was observed in muscle fibres from the temperate and Antarctic species. Chapter 3. 1. Fast and slow muscle fibres were isolated from the myotomes of atlantic cod (Gadus morhua L.) and short-horned sculpin (Myoxocephalus scorpius L.). 2. Epinephrine was found to have no effect on twitch or sub-tetanic contractions in fast muscle fibres. 3. Isoprenaline (10-6M) had no effect on the contractility of slow muscle fibres. 4. In contrast, epinephrine elicited a dose-dependent decrease in the half-time for twitch relaxation (t1/2r), and in most cases a decrease in twitch amplitude. Chapter 4. 1. Fast muscle fibres were isolated from the abdominal myotomes of the short-horned ...
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