148
E. D. 9. CORNER AND ANTHONY Q. DAVIES
lO"C, 76% was ammonia-nitrogen and 18% amino-nitrogen: for
Euphuusia paciJica the values were 82% for ammonia-nitrogen, 13%
for amino nitrogen and 1% for urea nitrogen. At lower temperatures
the proportion excreted by both species as amino-nitrogen was significantly lower.
Corner et al. (1965) concluded that the difference between Harris's
(1959) excretion data for Acartia clausi and their own for Calanua
Jinmarchicus was not related to levels of available food, or different
methods of chemical analysis, but probably reflected the fact that
Acurtia is a very much smaller animal and therefore likely t o be much
more active metabolically. Support for this view came from the finding
that nitrogen excretion by the younger stages of Calanus Jinmurchicua
(Copepodites 11, I11 and IV) was 21.6 pg/mg dry body weightlday
compared with a value of 9.8 for adults. The dry body weight of the
mixed young stages (24.6 pglanimal) was still considerably greater than
that of the Acurtia clausi used by Harris (5 pglanimal). However,
in a later study (Corner et al., 1967) data were obtained with nauplii
and copepodites I and I1 (with an average dry weight of 5-5 pg) and B
value of 38.1 pg N/mg dry body was obtained, reasonably close to that
of 43.1 found by Harris.
I n addition to food level, temperature and body-size as factors
influencing nitrogen excretion, salinity may also have an effect. Thus,
Raymont et al. (1968) have shown that Neomysis integer normally
excretes 24 pg N/mg dry weightlday; but animals adapted t o full
strength sea water and subsequently transferred t o 1% sea water
show a temporary increase in excretion rate that can reach six times the
normal value over the first two hours after transfer.
The first attempt t o measure nitrogen excretion using a carnivorous
species of zooplankton was that of Beers (1964) who found that the
chaetognath Sagitta hispida Conant collected from St. George's Harbour,
Bermuda, excreted ammonia a t an average rate of 12.7 pg/mg dry body
weightiday, a value equivalent to 14.5% of the total body nitrogen.
No food was given to the animals during the 24 h excretion experiment
and so the value probably represents a '' basal '' rate of nitrogen
excretion.
Because changes in temperature and food level affect nitrogen excretion by Calanus it seemed likely that the animals might excrete different
amounts at different seasons. Seasonal variation was studied by
Conover and Corner (1968), most of the data being obtained with the
boreal-arctic species Calanus hyperboreus used in excretion experiments
carried out a t P6OC. The animals were feeding during the experiments,
either on natural particulate material or laboratory cultures of phyto-
E. D. 9. CORNER AND ANTHONY Q. DAVIES
lO"C, 76% was ammonia-nitrogen and 18% amino-nitrogen: for
Euphuusia paciJica the values were 82% for ammonia-nitrogen, 13%
for amino nitrogen and 1% for urea nitrogen. At lower temperatures
the proportion excreted by both species as amino-nitrogen was significantly lower.
Corner et al. (1965) concluded that the difference between Harris's
(1959) excretion data for Acartia clausi and their own for Calanua
Jinmarchicus was not related to levels of available food, or different
methods of chemical analysis, but probably reflected the fact that
Acurtia is a very much smaller animal and therefore likely t o be much
more active metabolically. Support for this view came from the finding
that nitrogen excretion by the younger stages of Calanus Jinmurchicua
(Copepodites 11, I11 and IV) was 21.6 pg/mg dry body weightlday
compared with a value of 9.8 for adults. The dry body weight of the
mixed young stages (24.6 pglanimal) was still considerably greater than
that of the Acurtia clausi used by Harris (5 pglanimal). However,
in a later study (Corner et al., 1967) data were obtained with nauplii
and copepodites I and I1 (with an average dry weight of 5-5 pg) and B
value of 38.1 pg N/mg dry body was obtained, reasonably close to that
of 43.1 found by Harris.
I n addition to food level, temperature and body-size as factors
influencing nitrogen excretion, salinity may also have an effect. Thus,
Raymont et al. (1968) have shown that Neomysis integer normally
excretes 24 pg N/mg dry weightlday; but animals adapted t o full
strength sea water and subsequently transferred t o 1% sea water
show a temporary increase in excretion rate that can reach six times the
normal value over the first two hours after transfer.
The first attempt t o measure nitrogen excretion using a carnivorous
species of zooplankton was that of Beers (1964) who found that the
chaetognath Sagitta hispida Conant collected from St. George's Harbour,
Bermuda, excreted ammonia a t an average rate of 12.7 pg/mg dry body
weightiday, a value equivalent to 14.5% of the total body nitrogen.
No food was given to the animals during the 24 h excretion experiment
and so the value probably represents a '' basal '' rate of nitrogen
excretion.
Because changes in temperature and food level affect nitrogen excretion by Calanus it seemed likely that the animals might excrete different
amounts at different seasons. Seasonal variation was studied by
Conover and Corner (1968), most of the data being obtained with the
boreal-arctic species Calanus hyperboreus used in excretion experiments
carried out a t P6OC. The animals were feeding during the experiments,
either on natural particulate material or laboratory cultures of phyto-