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Y. Olsen
nivorous species with low EFA requirements. It is ubiquitous in nature, although
not very abundant.
The situation in Figure 8. I 8 is purely speculative. It illustrates, however, that
the ecological impact of EFA deficiency may be pronounced under the conditions
assumed above. The assumption that EFA deficiency affects reproduction and
survival of early developmental stages is robust. It is also obvious that species that
show reduced reproduction and growth will be less abundant compared with other
species. What is then left for further elaboration and speculation is the extent to
which that EFA requirements vary between animal species.
8.3. Concluding Remarks
Research on EFA requirements of cultivated marine fish has been extensive
during the past decade, and the present chapter has highlighted some lessons
learned concerning fatty acid metabolism and trophic transport and metabolism.
There are major similarities between zooplankton and fish that store TAGs, and
species-specific evolutionary adaptation to temperature is suggested to be important for their EFA requirements. Two different strategies are evident in the way
that animals metabolize DHA, which is by far the most important fatty acid during
physiological adaptation to low temperature. Many marine zooplankton species
store WEs, and this will strongly affect both metabolism and transport of fatty
acids and lipids. These species are very important food for harvested commercial
species but not in mariculture. They have therefore not been treated here.
Another lesson learned is that studies of EFA dynamics of zooplankton and fish
must be based on the understanding that PLs of cell membranes have important
structural and metabolic functions, whereas TAGs and WEs are primarily energy
depots. Sophisticated metabolic studies must involve fatty acid composition of
individual PLs of the membranes. The general compartment model, constituting
pools of metabolic active lipids and metabolic passive lipids, is important for
interpreting EFA dynamics and contents of all animals.
Data for total contents of w3 and w6 fatty acids, which represent the two
families of EFAs, cannot adequately express food quality, at least not for marine
cold-blooded animals. It is therefore necessary to consider individual EFAs within
the two families. This is another important lesson learned in mariculture. It will
probably be adequate to include the C20 and C22 EFAs in studies of marine
organisms, but one can still not take for granted that C 18 moieties are unimportant
for freshwater organisms with high metabolic flexibility to elongate short EFA.
Acknowledgments. The late Professor Harald Skjervold challenged me, in our
joint research on w3 fatty acids, to explore the space between human health and
mariculture. I will always be grateful for his great inspiration. I also thank my
colleagues from the university and SINTEF who have contributed to making this
chapter possible.
Y. Olsen
nivorous species with low EFA requirements. It is ubiquitous in nature, although
not very abundant.
The situation in Figure 8. I 8 is purely speculative. It illustrates, however, that
the ecological impact of EFA deficiency may be pronounced under the conditions
assumed above. The assumption that EFA deficiency affects reproduction and
survival of early developmental stages is robust. It is also obvious that species that
show reduced reproduction and growth will be less abundant compared with other
species. What is then left for further elaboration and speculation is the extent to
which that EFA requirements vary between animal species.
8.3. Concluding Remarks
Research on EFA requirements of cultivated marine fish has been extensive
during the past decade, and the present chapter has highlighted some lessons
learned concerning fatty acid metabolism and trophic transport and metabolism.
There are major similarities between zooplankton and fish that store TAGs, and
species-specific evolutionary adaptation to temperature is suggested to be important for their EFA requirements. Two different strategies are evident in the way
that animals metabolize DHA, which is by far the most important fatty acid during
physiological adaptation to low temperature. Many marine zooplankton species
store WEs, and this will strongly affect both metabolism and transport of fatty
acids and lipids. These species are very important food for harvested commercial
species but not in mariculture. They have therefore not been treated here.
Another lesson learned is that studies of EFA dynamics of zooplankton and fish
must be based on the understanding that PLs of cell membranes have important
structural and metabolic functions, whereas TAGs and WEs are primarily energy
depots. Sophisticated metabolic studies must involve fatty acid composition of
individual PLs of the membranes. The general compartment model, constituting
pools of metabolic active lipids and metabolic passive lipids, is important for
interpreting EFA dynamics and contents of all animals.
Data for total contents of w3 and w6 fatty acids, which represent the two
families of EFAs, cannot adequately express food quality, at least not for marine
cold-blooded animals. It is therefore necessary to consider individual EFAs within
the two families. This is another important lesson learned in mariculture. It will
probably be adequate to include the C20 and C22 EFAs in studies of marine
organisms, but one can still not take for granted that C 18 moieties are unimportant
for freshwater organisms with high metabolic flexibility to elongate short EFA.
Acknowledgments. The late Professor Harald Skjervold challenged me, in our
joint research on w3 fatty acids, to explore the space between human health and
mariculture. I will always be grateful for his great inspiration. I also thank my
colleagues from the university and SINTEF who have contributed to making this
chapter possible.