Temperature is known to affect fish growth, and in Atlantic salmon there is an influence on muscle cellularity. Primary muscle cell culture makes it possible to investigate direct effects of temperature on myogenic cells. Salmon myosatellite cells were cultured for the first time in this study. The cells were cultured at either 5 degrees C or 11 degrees C. Increased temperature led to an increase in differentiation rate and especially hypertrophic growth (Q10 = 4.0). No nuclear proliferation was evident in the satellite cell population isolated at either temperature. This may be due to the presence of different subpopulations of myogenic cells at different developmental ages or the presence of indirect factors in vivo.

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Muscle cellularity at a developmental stage around the time of hatching was examined in rainbow trout which had been reared from the eyed stage at three different temperature regimes (5, 10 and 15 C) and different O 2 tensions [70% of air saturation value (ASV) at 5 C, 100% of ASV at all temperatures, and 150% of ASV at 10 and 15 C]. It was found that, as has been shown for other species, there was a difference in muscle fibre numbers and fibre cross-sectional areas between some of the regimes. There was a decrease in fibre number at the intermediate and higher temperature, and a decrease in fibre size at the high temperature. The temperature effects observed were modified by the applied changes in O 2 tension. An increased O 2 tension at 10 C led to an increase in fibre size whereas a decrease in O 2 tension at the low temperature resulted in a decrease in fibre number. The largest total white muscle cross-sectional area was achieved at 10 C under high O 2 conditions. Temperature and O 2 tension therefore had a clear effect on muscle cellularity and there was a significant interaction between the two parameters.1998 The Fisheries Society of the British Isles