302
J. H. S. BLAXTER AND F. 0. T. HOLLIDAY
that the dietary fat of Sardinqs caerulea (derived to a large extent
from Calanus) was stored largely unaltered. They also showed that
both the blood lipids and the lipids deposited in the gonad were practically identical, indicating that mobilization of fats from the intestine
to the gonads was relatively direct. The lipids of the developing eggs
caught st sea were almost identical with those from the eggs at different
stages of maturation in the gonad. Changes were shown to occur in the
fatty acid pattern of the lipids of the blood, gonad and mesenteries
when the sardines were fed on an artificial diet. The herring does have
the capacity to alter the fatty acid composition of the depot lipids,
especially in regard to the degree of unsaturation of the fat, but the
rapid ingestion of the highly unsaturated fats during the intense
feeding periods causes a temporary swamping of the fishes' hydrogenation mechanisms (Lovern, 1938).
Cholesterol does not show the same kind of changes as the fatty
acids. The level remains constant in the muscles, there being a slow
transfer of cholesterol from the liver and mesenteries to the gonads,
where cholesterol levels rise with the degree of maturation. The testis
contains considerably more cholesterol than the ovary. Channon and
$aby (1932) demonstrated that during the final stages of maturation
more cholesterol was present in the gonad then could be accounted for
in the depots, and they concluded that at this time the herring waa
synthesizing cholesterol.
4. General
The food available for metabolism, either from an external source
or from the fat depots, obviouxly profoundly influenccu the timing and
rate of many of the other physifhJgicd ar:tivitif:n. J 1, i8 riot nurprinirrg
then that at least loose correlation^ can t x made tJCtWf:<:rl fatnfm arid
fecundity, maturation rate, age, growth r:tc. MoHt estimaks of thc
" condition factor " of clupcids reflect to a largc: di?grcA: thc Htate of the
fat stores. A good deal of work fitill remain8 to tjc donc on tho coofrolations between fatness and gonad state, growth rtitc, ctc., but at a
more fundamental level than that of Rtatistical correlation. A lot also
remains to be done on the mechanisms involved in the metabolism of
tho oily diet of thc clupeids, especially on the fate of the metabolic
by-products.
1. Metiwds of calculation
Growth rates for thc herring in the sea have been calculated by
plotting tho mean length or increment of length, against age, or by back
E. Growth
J. H. S. BLAXTER AND F. 0. T. HOLLIDAY
that the dietary fat of Sardinqs caerulea (derived to a large extent
from Calanus) was stored largely unaltered. They also showed that
both the blood lipids and the lipids deposited in the gonad were practically identical, indicating that mobilization of fats from the intestine
to the gonads was relatively direct. The lipids of the developing eggs
caught st sea were almost identical with those from the eggs at different
stages of maturation in the gonad. Changes were shown to occur in the
fatty acid pattern of the lipids of the blood, gonad and mesenteries
when the sardines were fed on an artificial diet. The herring does have
the capacity to alter the fatty acid composition of the depot lipids,
especially in regard to the degree of unsaturation of the fat, but the
rapid ingestion of the highly unsaturated fats during the intense
feeding periods causes a temporary swamping of the fishes' hydrogenation mechanisms (Lovern, 1938).
Cholesterol does not show the same kind of changes as the fatty
acids. The level remains constant in the muscles, there being a slow
transfer of cholesterol from the liver and mesenteries to the gonads,
where cholesterol levels rise with the degree of maturation. The testis
contains considerably more cholesterol than the ovary. Channon and
$aby (1932) demonstrated that during the final stages of maturation
more cholesterol was present in the gonad then could be accounted for
in the depots, and they concluded that at this time the herring waa
synthesizing cholesterol.
4. General
The food available for metabolism, either from an external source
or from the fat depots, obviouxly profoundly influenccu the timing and
rate of many of the other physifhJgicd ar:tivitif:n. J 1, i8 riot nurprinirrg
then that at least loose correlation^ can t x made tJCtWf:<:rl fatnfm arid
fecundity, maturation rate, age, growth r:tc. MoHt estimaks of thc
" condition factor " of clupcids reflect to a largc: di?grcA: thc Htate of the
fat stores. A good deal of work fitill remain8 to tjc donc on tho coofrolations between fatness and gonad state, growth rtitc, ctc., but at a
more fundamental level than that of Rtatistical correlation. A lot also
remains to be done on the mechanisms involved in the metabolism of
tho oily diet of thc clupeids, especially on the fate of the metabolic
by-products.
1. Metiwds of calculation
Growth rates for thc herring in the sea have been calculated by
plotting tho mean length or increment of length, against age, or by back
E. Growth