Tw. Matschak et al., OXYGEN AVAILABILITY AND TEMPERATURE AFFECT EMBRYONIC MUSCLE DEVELOPMENT IN ATLANTIC SALMON (SALMO-SALAR L), Differentiation, 61(4), 1997, pp. 229-235
In Atlantic salmon, muscle fibre hypertrophy (increase in fibre cross-
sectional area) and muscle fibre hyperplasia (increase in muscle fibre
number) are differentially affected by the incubation temperature dur
ing embryonic development. This affects muscle cellularity (number and
mean cross-sectional area of the fibres) at hatching and can affect p
osthatch growth. When the egg capsule, an oxygen barrier, is removed t
emperature has a different effect on muscle cellularity. Oxygen levels
may thus play a role in the muscle development of late embryos. The e
ffect of different oxygen levels (50%, 100% and 150% air saturation le
vel) and temperatures (5 degrees C and 10 degrees C) during late embry
onic development on the muscle cellularity at a developmental stage ju
st before hatching was therefore investigated. Fibre numbers at 100% a
ir saturation were 17% lower at 10 degrees C in the presence of the eg
g capsule (chorionated) whereas no difference between temperature regi
mes was found in its absence (dechorionated). Under low oxygen conditi
ons a reduction in fibre numbers (-12%) was found at 5 degrees C in ch
orionated embryos, whereas no effect was found in the dechorionated gr
oups. Muscle fibre cross-sectional area was affected also by oxygen le
vels with lowered O-2 leading to a reduction. An increase in temperatu
re also led to a reduction in fibre cross-sectional area. Furthermore,
nuclear numbers in the presumptive white muscle were strongly affecte
d. Removal of the egg capsule caused an increase in nuclear numbers at
both temperatures (5 degrees C: +40%, 10 degrees C: +70%). The oxygen
level only affected nuclear numbers at 10 degrees C: an increase of 4
6% was found at the increased O-2 level in chorionated embryos, wherea
s a reduction by 26% was observed at the low O-2 level in the dechorio
nated group. O-2 levels therefore clearly affected muscle cellularity
in a temperature-dependent way. Overall the results suggest that O-2 a
vailability is a significant contributing factor to temperature effect
s during late muscle development in Atlantic salmon embryos.