Variation of storage lipid quantity with body size and season in fifth
copepodites of Calanus finmarchicus from Georges Bank and the
Gulf of Maine
C. B. Miller, J. Crain and C. Morgan
Oil sac volume has
been estimated in live fifth copepodites (C5) of Calanus
finmarchicus using video images of the side view. Careful
attention has been paid to details of the approximate volume
integration, and a new method is proposed. The upper limit of stored
wax volume increases with body size both absolutely and as a fraction
of prosome volume, because relatively more space is available for wax
in large (2.8 mm prosome) than in small (1.6 mm prosome) C5. Actual
amounts stored vary from the maximum for the body size to near zero
from January through June at all depths and all sites in the vicinity
of Georges Bank. Nevertheless there are trends. January specimens
mostly retain less oil than June specimens, presumably due to some
use over the summer-autumn diapause. Reduction is more advanced in
February for the few C5 remaining. During April, as the winter
spring generation (G1) completes development, C5 of all degrees of
relative fullness are present. More are near the maximum in May and
June. After factoring out body size, most C5 collected at depth
during spring and early summer hold more wax than most of those
collected near the surface. Patterns of data density on plots of
oil sac volume versus prosome size do not, however, always shift with
season and depth in a simple, readily interpreted manner.