Egg production
and energy storage in relation to feeding conditions in the subantarctic
calanoid copepod Drepanopus pectinatus: an experimental study of
reproductive strategy
F.
Alonzo, P. Mayzaud, S. Razouls-2001
Marine Ecology Progress Series, 209: 231-242
(from Current Contents)
Abstract :
The egg production and the hatching success of
Drepanopus pectinatus (Brady, 1883) was examined in relation to food
availability. The spawning frequency did not change in relation to the
concentration of phytoplankton with an interval time of 7.6 d between 2
broods. At least 1 egg sac was produced per female in almost all cases (>
93 %) independent of the food level. The subsequent recruitment of breeding
females was strongly influenced by feeding conditions: only 22 to 50 % of
the starved females completed 3 successive breeding cycles, while 100% of
the fed females did. The number of eggs per was also affected by the
concentration of food, with a mean of 12 eggs per sac in starved females and
19.4 eggs per sac in fed females independent of the food level. Brood sizes
increased significantly in the fourth breeding cycle to 35.3 eggs per sac in
females fed a concentration of 1180 pg protein 1(-1). Egg-hatching time was
constant, with an average of 6.7 d. To evaluate the relative roles of
reproduction and of accumulation of energy reserves, we compared the
production of eggs and the changes in the organic composition of females in
various limiting food conditions. Brood size was influenced by both
immediate and past trophic conditions, with the number of eggs per sac
varying from 10.1 to 12.8. The content of the eggs was constant: 122 ng of
protein and 234 ng of Lipids. In females, protein content was a good
indicator of immediate feeding conditions, while lipids, dominated by wax
esters, reflected both immediate and past feeding conditions. A low level of
egg production was maintained throughout periods of nutritional limitation
or starvation. Subsequently, food was used to reduce the consumption of the
energy reserves of females before being invested in reproduction, as
observed at high food concentration.
(ESA, CNRS 7076, BP 28,
F-06230 Villefranche Sur Mer, France, e-mail : alonzo@obs-vlfr.fr)