164
E. D. 9. CORNER AND ANTHONY 0. DAVIES
growth at higher temperatures was also observed by Heinle (1966)
using Acartia tonsa cultured on the natural food available in the
Patuxent Estuary. The time for development from " egg to egg '' waa
found to be 13, 9 and 7 days at 15.5, 22.4 and 254°C respectively.
Mullin and Brooks (1970) also showed that quality of diet affected
growth rate. Thus, in experiments using Rhincalanus nasutus reared
at 15"C, full growth was achieved in 23 days on a diet of Ditylum
brightwellii, but required 36 days when the food was Thalassiosira
jluviatilis.
The field studies of Deevey (1960) have led to the generalization
that copepods growing at low temperatures will be larger in size at
any stage of development compared with animals of the same species
growing at higher temperatures. However, Mullin and Brooks (1970)
found no significant difference in carbon content between Calanw
reared at 10 and 15OC on a diet of Thalassiosira ; and obtained a similar
result with Rhincalanus nusutus reared on this diet. Further observations with the latter species also indicated that type of food had no
sensible effect on size, inasmuch as animals reared on Dilylum or
Thalassiosira did not significantly differ in carbon content. On the
other hand, the quantity of food given does seem to affect size, for
Paffenhiifer (1969) has found that the length of female Calanus helgolandicw feeding on the chain-forming diatom Lauderiu borealis ranges
from 3-03 to 3-67 mm, depending on the level of food available.
Possibly, now that a growing number of zooplanktonic species can be
successfully cultured in the laboratory, the effects of temperature and
the quality and quantity of food on the levels of nitrogen and phosphorus present in the animals can be studied.
The exponential portion of the sigmoid growth curve (egg to
copepodite V, Fig. 8) is represented by the equation W, = Woekt,
where W, is the amount of any body constituent (carbon, nitrogen, etc.)
after t days, W, is the quantity in the egg, t is the time increment and k
is a rate coefficient (larger k values indicating more rapid development).
In terms of body nitrogen, Corner et al. (1967) calculated a value of k of
0-24 for Calanus finmarchicus : but corresponding data for body
phosphorus have not yet been obtained.
Further data, described by Mullin and Brooks (1970) indicate that
k values can vary considerably with temperature, type of food and
stage of development. Thus, for Rhinealanus nasutus feeding on
Thalassiosira at 10°C, Mullin and Brooks found k values of 0.13
(nauplius I to copepodite I), 0.15 (copepodite I to copepodite IV) and
0.06 (copepodite I V to adult). Corresponding valuee at 15OC were
0.15, 0.22 and 0.18 respectively. When Ditylum was used as a food the
E. D. 9. CORNER AND ANTHONY 0. DAVIES
growth at higher temperatures was also observed by Heinle (1966)
using Acartia tonsa cultured on the natural food available in the
Patuxent Estuary. The time for development from " egg to egg '' waa
found to be 13, 9 and 7 days at 15.5, 22.4 and 254°C respectively.
Mullin and Brooks (1970) also showed that quality of diet affected
growth rate. Thus, in experiments using Rhincalanus nasutus reared
at 15"C, full growth was achieved in 23 days on a diet of Ditylum
brightwellii, but required 36 days when the food was Thalassiosira
jluviatilis.
The field studies of Deevey (1960) have led to the generalization
that copepods growing at low temperatures will be larger in size at
any stage of development compared with animals of the same species
growing at higher temperatures. However, Mullin and Brooks (1970)
found no significant difference in carbon content between Calanw
reared at 10 and 15OC on a diet of Thalassiosira ; and obtained a similar
result with Rhincalanus nusutus reared on this diet. Further observations with the latter species also indicated that type of food had no
sensible effect on size, inasmuch as animals reared on Dilylum or
Thalassiosira did not significantly differ in carbon content. On the
other hand, the quantity of food given does seem to affect size, for
Paffenhiifer (1969) has found that the length of female Calanus helgolandicw feeding on the chain-forming diatom Lauderiu borealis ranges
from 3-03 to 3-67 mm, depending on the level of food available.
Possibly, now that a growing number of zooplanktonic species can be
successfully cultured in the laboratory, the effects of temperature and
the quality and quantity of food on the levels of nitrogen and phosphorus present in the animals can be studied.
The exponential portion of the sigmoid growth curve (egg to
copepodite V, Fig. 8) is represented by the equation W, = Woekt,
where W, is the amount of any body constituent (carbon, nitrogen, etc.)
after t days, W, is the quantity in the egg, t is the time increment and k
is a rate coefficient (larger k values indicating more rapid development).
In terms of body nitrogen, Corner et al. (1967) calculated a value of k of
0-24 for Calanus finmarchicus : but corresponding data for body
phosphorus have not yet been obtained.
Further data, described by Mullin and Brooks (1970) indicate that
k values can vary considerably with temperature, type of food and
stage of development. Thus, for Rhinealanus nasutus feeding on
Thalassiosira at 10°C, Mullin and Brooks found k values of 0.13
(nauplius I to copepodite I), 0.15 (copepodite I to copepodite IV) and
0.06 (copepodite I V to adult). Corresponding valuee at 15OC were
0.15, 0.22 and 0.18 respectively. When Ditylum was used as a food the