Zooplankton growth rates: diel egg production in the copepods Oithona, Euterpina and Corycaeus from tropical waters

Clear diel periodicity in the timing of egg laying was observedin the tropical cyclopoid cope-pods Oithona plumifera, Oithonanana, Oithona simplex and Corycaeus amazomcus, and the harpacti-coidEuterpina acutifrons in waters surrounding Jamaica, West Indies.Individual females incubated under ambient food conditions formultiple clutches displayed remarkable constancy in their clutchdurations (= egg or embryonic development time). All speciesexhibited clutch durations of 20–23 h and cycle durations(= sum of clutch and inter-clutch durations) of 24 h, exceptfor the offshore species O.plumifera where the clutch durationwas 36 h and the cycle duration 48 or 72 h. Egg laying appearedto be synchronized by photoperiod, occurring around dawn formost species. In order to avoid biases, diel periodicity mustbe accounted for in estimates of egg production rates, and futureefforts should concentrate on the responses of clutch size andinterclutch durations to natural food climates.