Effects of Varying Food Concentrations on Reproduction in Diaptomus clavipes Schacht

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Abstract
Copepods may respond to food shortages by ceasing egg production and possibly mating activity or by producing small clutches with large eggs. Data on egg production of the calanoid copepod, D. clavipes Schacht, were obtained for 4 food concentrations in a 21 day experiment at a constant temperature and density. Number of eggs per clutch, total clutch volume, individual egg volume, number of attached spermatophores per female and condition of the ovaries were determined daily. Clutch size (number of eggs per clutch and total clutch volume) was directly related to food concentration, while individual egg volumes were inversely related to food concentration. Rate of clutch production was not significantly affected by food concentration except under starvation conditions. Starved females initially produced small clutches with large eggs followed by a cessation of egg production. These females usually had no egg material visible in the ovaries or attached spermatophores. Production of large eggs under food stress would have ecological significance if they gave rise to larger or more fit nauplii.