11. HYDROSTATIC PRESSURE
457
sideration has been given to phenomena at the biochemical, cellular, and
tissue levels, as well as to whole organisms. However, compared with
what might be done, very little has been done.
Biochemical comparisons between deep-sea and shallow water fishes
to date have not uncovered any differences which can be unequivocally
attributed to the effects of increased pressure. Only fragmentary data
are available on tissue metabolic rates and pathways for carbohydrate
metabolism in a few mesopelagic species (Soprunov, 1968).
Lewis (1962, 1967) has studied the abundances of fatty acids of
different chain lengths and degrees of unsaturation in the lipids of a
variety of species of epi-, meso-, and bathypelagic fishes, also several
benthic species from various depths. His results indicate a general trend
of decreasing abundance of medium-chain-length saturated and longchain-length polyunsaturated acids with increasing depth, while oleic
acid greatly increases.
Similar results have been obtained by Nevenzel et al. (1965, 1966,
1969) on many species of mesopelagic fishes. Nevenzel et al. have shown
that the unusual chain-length distribution in these species results from
the occurrence of large proportions of wax esters, rather than glyceryl
esters, in the lipids. Reasons for this difference are not apparent, although there may be small differences between the specific gravities
of two types of lipids which may be of some significance in buoyancy
control. However, similar fatty acid chain-lcngth distributions occur in
deep-sea benthic fishes and crustaceans ( Lewis, 1967). Lewis argues
that the wax esters in these latter forms may derive from feeding on
bathypelagic species. The causative factors underlying this fundamental
biochemical difference remain to be determined.
The author has made a similar survey of a variety of littoral, epipelagic, and mesopelagic fishes with respect to the spectrum of abundances of free amino acids and similar substances in the muscles. This
survey has found no statistically reliable differences in terms of either
absolute or relative abundance of 18 ninhydrin-positive compounds between the various groups. Variables taken into account in the statistical
analysis of the results of about 120 analyses carried out on a Beckman
Model 120B amino acid analyzer included systematic position of the
species, water depth, water temperature, and geographical area. It is
possible that variability between duplicate samples resulting from technical difficulties in sample preparation under field (oftentimes shipboard ) conditions may have obliterated some small differences between
the various groups. However, differences comparable in magnitude to
those occurring among the lipids should have been clearly detected
(Gordon and Yuen, 1969).
All other biochemical studies relating to pressure and involving
457
sideration has been given to phenomena at the biochemical, cellular, and
tissue levels, as well as to whole organisms. However, compared with
what might be done, very little has been done.
Biochemical comparisons between deep-sea and shallow water fishes
to date have not uncovered any differences which can be unequivocally
attributed to the effects of increased pressure. Only fragmentary data
are available on tissue metabolic rates and pathways for carbohydrate
metabolism in a few mesopelagic species (Soprunov, 1968).
Lewis (1962, 1967) has studied the abundances of fatty acids of
different chain lengths and degrees of unsaturation in the lipids of a
variety of species of epi-, meso-, and bathypelagic fishes, also several
benthic species from various depths. His results indicate a general trend
of decreasing abundance of medium-chain-length saturated and longchain-length polyunsaturated acids with increasing depth, while oleic
acid greatly increases.
Similar results have been obtained by Nevenzel et al. (1965, 1966,
1969) on many species of mesopelagic fishes. Nevenzel et al. have shown
that the unusual chain-length distribution in these species results from
the occurrence of large proportions of wax esters, rather than glyceryl
esters, in the lipids. Reasons for this difference are not apparent, although there may be small differences between the specific gravities
of two types of lipids which may be of some significance in buoyancy
control. However, similar fatty acid chain-lcngth distributions occur in
deep-sea benthic fishes and crustaceans ( Lewis, 1967). Lewis argues
that the wax esters in these latter forms may derive from feeding on
bathypelagic species. The causative factors underlying this fundamental
biochemical difference remain to be determined.
The author has made a similar survey of a variety of littoral, epipelagic, and mesopelagic fishes with respect to the spectrum of abundances of free amino acids and similar substances in the muscles. This
survey has found no statistically reliable differences in terms of either
absolute or relative abundance of 18 ninhydrin-positive compounds between the various groups. Variables taken into account in the statistical
analysis of the results of about 120 analyses carried out on a Beckman
Model 120B amino acid analyzer included systematic position of the
species, water depth, water temperature, and geographical area. It is
possible that variability between duplicate samples resulting from technical difficulties in sample preparation under field (oftentimes shipboard ) conditions may have obliterated some small differences between
the various groups. However, differences comparable in magnitude to
those occurring among the lipids should have been clearly detected
(Gordon and Yuen, 1969).
All other biochemical studies relating to pressure and involving