146
E. D. 5. CORNER AND ANTHONY Q. DAVIES
for winter animals 1.8%. The quantities of amino acids, both free and
combined as peptides and proteins, in the related species Calanus
jinmarchicus had earlier been estimated by Cowey and Corner (1 963a)
as representing 11% of the wet weight of the animals. Therefore,
assuming a wct weight : dry weight ratio of 6 : 1 , the starving Calanus
lost 3.1% of their total amino acid content daily in summer, and 2.7%
in winter.
These values are an order of magnitude lower than those of Harris
(1959) for Acartia, probably because the Calanus had been starved over
a prolonged period. Corner et al. (1965) therefore measured nitrogen
excretion by feeding Calanus, in a manner similar to that of Harris
(1959), but with the added refinement that a correction factor was
made for the small uptake of excreted ammonia by the plant food.
Bacteria-free algal diets were used at various cell concentrations and it
was found that nitrogen excretion increased with the food level.
However, the increase was relatively small, a ten-fold rise in food
concentration from 16 to 160 pg N/1. resulting only in an increase in
nitrogen excretion from 9.3 to 12-2 pglmg dry weightlday (average
values). The animals were therefore excreting approximately 8-1 1 %
of their body nitrogen daily, a level of excretion considerably higher
than that found by Cowey and Corner (1963b) for Calanus starved over
a long period, but still much lower than that found by Harris (1959)
for Acartia.
The average temperature used in the experiments with Acartia WM
13"C, compared with 10°C in those with Calanus. Corner et al. (1965)
found that nitrogen excretion increased by a factor of 1.8 as the temperature was raised from 5 t o 15°C ; but the increase was too small to
account for the difference between the excretion data for Calanus and
those for Acartia.
Harris used the method of Riley (1953) to estimate ammonia, but
the procedure used by Corner et al. (1965) was an adaptation of the
ninhydrin method described by Moore and Stein (1954). Ninhydrin
reacts with nitrogenous substances other than ammonia (e.g. amino
acids) but no significant difference was found between the levels of
ammonia as determined by the ninhydrin procedure or Nesslerization
(Barnes, 1959) or steam-distillation in a Kjeldahl apparatus. Corner
et al. (1965) therefore concluded that significant quantities of nitrogenous substances other than ammonia were not excreted by Calanus.
Moreover, had the plant cells been inefficiently captured and the contents " spilled ", or had they been incompletely digested, free amino
acids contained in the algae could well have appeared in considerable
quantities among the ninhydrin-positive substances present in the sea
E. D. 5. CORNER AND ANTHONY Q. DAVIES
for winter animals 1.8%. The quantities of amino acids, both free and
combined as peptides and proteins, in the related species Calanus
jinmarchicus had earlier been estimated by Cowey and Corner (1 963a)
as representing 11% of the wet weight of the animals. Therefore,
assuming a wct weight : dry weight ratio of 6 : 1 , the starving Calanus
lost 3.1% of their total amino acid content daily in summer, and 2.7%
in winter.
These values are an order of magnitude lower than those of Harris
(1959) for Acartia, probably because the Calanus had been starved over
a prolonged period. Corner et al. (1965) therefore measured nitrogen
excretion by feeding Calanus, in a manner similar to that of Harris
(1959), but with the added refinement that a correction factor was
made for the small uptake of excreted ammonia by the plant food.
Bacteria-free algal diets were used at various cell concentrations and it
was found that nitrogen excretion increased with the food level.
However, the increase was relatively small, a ten-fold rise in food
concentration from 16 to 160 pg N/1. resulting only in an increase in
nitrogen excretion from 9.3 to 12-2 pglmg dry weightlday (average
values). The animals were therefore excreting approximately 8-1 1 %
of their body nitrogen daily, a level of excretion considerably higher
than that found by Cowey and Corner (1963b) for Calanus starved over
a long period, but still much lower than that found by Harris (1959)
for Acartia.
The average temperature used in the experiments with Acartia WM
13"C, compared with 10°C in those with Calanus. Corner et al. (1965)
found that nitrogen excretion increased by a factor of 1.8 as the temperature was raised from 5 t o 15°C ; but the increase was too small to
account for the difference between the excretion data for Calanus and
those for Acartia.
Harris used the method of Riley (1953) to estimate ammonia, but
the procedure used by Corner et al. (1965) was an adaptation of the
ninhydrin method described by Moore and Stein (1954). Ninhydrin
reacts with nitrogenous substances other than ammonia (e.g. amino
acids) but no significant difference was found between the levels of
ammonia as determined by the ninhydrin procedure or Nesslerization
(Barnes, 1959) or steam-distillation in a Kjeldahl apparatus. Corner
et al. (1965) therefore concluded that significant quantities of nitrogenous substances other than ammonia were not excreted by Calanus.
Moreover, had the plant cells been inefficiently captured and the contents " spilled ", or had they been incompletely digested, free amino
acids contained in the algae could well have appeared in considerable
quantities among the ninhydrin-positive substances present in the sea