170
E. D. 9. CORNER AND ANTHONY 0. DAVIES
As noted earlier (p. 140) these values, calculated at a period of the year
when conditions in the Clyde Sea-area should have favoured “ superfluous feeding ”, are much higher than the poor levels of assimilation
(22-33 %) used by Beklemishev (1962).
Butler et al. (1970) made use of these data in preparing nitrogen and
phosphorus “ budgets ” for spring growth by stage V, male and female
Calanus Jinmurchicus in the Clyde. They found that of the total
nitrogen captured each day. 26.8% was invested in growth, 37.5% was
unassimilated and 35.7% was excreted in soluble form. Of captured
phosphorus, 17.2% was invested in growth, 23.0% was unassimilated
and 59.8% excreted in soluble form.
The sum of the quantities of nitrogen or phosphorus used for
growth, cxcreted in soluble form and voided as faecal material gave the
daily ‘‘ ration ” required by the animals. This value, in terms of body
nitrogen, was equivalent to 13.4% : that in terms of body phosphorus
was 1 7 4 % . These values are similar to the range of 11-14yo calculated by Harvey (1950) in terms of body carbon (see p. 138).
Values for K,(N) mid K,(P) were 42.7 and 22.3% respectively ; and
for K,(N) and K,(P) 26.8 and 17.2% respectively. These K , values for
growth by the more mature stages of the animals are lower than those
calculated for the wholc period of development from egg to adult, and
this observation is consistent with those of Petipa (1967) and Pavlova
(1967) whose budgets for copepods in terms of calories show that both
K, and K , values for growth by young stages are markedly higher than
those for older animals (see Table IX).
It is also interesting to note that the various data summarized in
Table I X show that generally the growth efficiency of copepods in terms
of egg production is lower than that calculated for growth from egg to
adult : although a possible explanation of this may be that the total
numbers of eggs produced have been undercstiniated (see p. 165).
Values of K, and K, may be affected by factors other than stage of
growth, one possibility being the level of availablc food. Thus, at times
of year when food is plentiful the animal will have to expend additional
energy in digesting and absorbing the large quantity of food it captures.
On the othcr hand, when food is scarce the animal will have to work
harder in order to capture its daily dict. This aspect of zooplankton
nutrition has not yet been examined in terms of nitrogen and phosphorus, but evidence that K , diminishes at higher food concentrations
has been found by Conover (1964) studying Calanus hyperboreus. Thus,
the average K , value obtained at food levels greater than 6 mg dry
weight/l was only 12-2%, compared with 25.3% at levels less than 3 mg
dry weightll.
E. D. 9. CORNER AND ANTHONY 0. DAVIES
As noted earlier (p. 140) these values, calculated at a period of the year
when conditions in the Clyde Sea-area should have favoured “ superfluous feeding ”, are much higher than the poor levels of assimilation
(22-33 %) used by Beklemishev (1962).
Butler et al. (1970) made use of these data in preparing nitrogen and
phosphorus “ budgets ” for spring growth by stage V, male and female
Calanus Jinmurchicus in the Clyde. They found that of the total
nitrogen captured each day. 26.8% was invested in growth, 37.5% was
unassimilated and 35.7% was excreted in soluble form. Of captured
phosphorus, 17.2% was invested in growth, 23.0% was unassimilated
and 59.8% excreted in soluble form.
The sum of the quantities of nitrogen or phosphorus used for
growth, cxcreted in soluble form and voided as faecal material gave the
daily ‘‘ ration ” required by the animals. This value, in terms of body
nitrogen, was equivalent to 13.4% : that in terms of body phosphorus
was 1 7 4 % . These values are similar to the range of 11-14yo calculated by Harvey (1950) in terms of body carbon (see p. 138).
Values for K,(N) mid K,(P) were 42.7 and 22.3% respectively ; and
for K,(N) and K,(P) 26.8 and 17.2% respectively. These K , values for
growth by the more mature stages of the animals are lower than those
calculated for the wholc period of development from egg to adult, and
this observation is consistent with those of Petipa (1967) and Pavlova
(1967) whose budgets for copepods in terms of calories show that both
K, and K , values for growth by young stages are markedly higher than
those for older animals (see Table IX).
It is also interesting to note that the various data summarized in
Table I X show that generally the growth efficiency of copepods in terms
of egg production is lower than that calculated for growth from egg to
adult : although a possible explanation of this may be that the total
numbers of eggs produced have been undercstiniated (see p. 165).
Values of K, and K, may be affected by factors other than stage of
growth, one possibility being the level of availablc food. Thus, at times
of year when food is plentiful the animal will have to expend additional
energy in digesting and absorbing the large quantity of food it captures.
On the othcr hand, when food is scarce the animal will have to work
harder in order to capture its daily dict. This aspect of zooplankton
nutrition has not yet been examined in terms of nitrogen and phosphorus, but evidence that K , diminishes at higher food concentrations
has been found by Conover (1964) studying Calanus hyperboreus. Thus,
the average K , value obtained at food levels greater than 6 mg dry
weight/l was only 12-2%, compared with 25.3% at levels less than 3 mg
dry weightll.