METABOLIC ENZYME-ACTIVITIES IN ATLANTIC SALMON (SALMO-SALAR L.) EMBRYOS RESPOND MORE TO CHRONIC CHANGES IN OXYGEN AVAILABILITY THAN TO ENVIRONMENTAL-TEMPERATURE
Tw. Matschak et al., METABOLIC ENZYME-ACTIVITIES IN ATLANTIC SALMON (SALMO-SALAR L.) EMBRYOS RESPOND MORE TO CHRONIC CHANGES IN OXYGEN AVAILABILITY THAN TO ENVIRONMENTAL-TEMPERATURE, Fish physiology and biochemistry, 18(2), 1998, pp. 115-123
Chronic exposure to an increased temperature (e.g., 10 degrees C as co
mpared to 5 degrees C) and to a different oxygen tension can dramatica
lly affect muscle cellularity in Atlantic salmon embryos at a developm
ental stage close to hatching. Maximal activities of enzymes of aerobi
c and anaerobic metabolism have been shown to vary with temperature an
d growth rates in fish but only limited data are available for embryon
ic fish. In order to obtain data on Atlantic salmon embryos and to be
able to compare temperature and oxygen effects, the maximal activities
of lactate dehydrogenase (LDH) and cytochrome c oxidase (CCO) were de
termined in body tissue containing mainly muscle as measures of anaero
bic and aerobic metabolism, respectively. Temperatures of 5 and 10 deg
rees C, different O-2 tensions (50% normoxic, normoxic, 150% normoxic)
, and growth within (chorionated) or without (dechorionated) the egg c
apsule were chosen as environmental conditions. Temperature affected C
CO activities and thus the CCO/LDH ratio in dechorionated but not in c
horionated embryos (5 < 10 degrees C) and had no effect on LDH activit
ies. However, changes in oxygen availability had an effect on all para
meters measured. Tissue protein concentration increased after dechorio
nation but no temperature effect was found. Both LDH and CCO activitie
s undergo complex responses to oxygen availability depending on incuba
tion temperature. There thus appeared to be an interaction of temperat
ure and oxygen availability with regard to maximum activities of key e
nzymes of the aerobic and anaerobic metabolism in the salmon embryos.