Étude de la ponte et du développement embryonnaire en relation avec la température et la nourriture chez Temora stylifera Dana (Copepoda:Calanoida)

Abstract

Egg production by the copepod Temora stylifera was significantly influenced by the algal composition of the diet. Egg production was higher with Hymenomonas elongata as food than with Phaeodactylum tricornutum, Skeletonema costatum or a mixture of the three species. Egg production increased also with concentration of food reaching a maximum of 277 ± 20 eggs per female in 7 days. The parameters of the equation describing this relation: γ = α(1−e t ̄ βχ ) + c were calculated for Temora stylifera fed Hymenomonas elongata. Egg production was measured in terms of carbon and nitrogen; it reached 131 % of the body weight of the adult in carbon and 53% of its body weight in nitrogen per 7 days. Influence of food and season on egg was also shown. Temperature had also a direct influence on egg production, with an optimum at 16°C (mean temperature in situ). The seasonal temperature in situ at which the female copepod matured, seemed to influence the acute response of egg production to temperature. Seasonal variations in egg production were shown with a maximum in autumn and a decrease in winter and spring corresponding with seasonal fluctuations in the adult population and the chlorophyll concentration in the sea. An equation was fitted to the eggs development time (hatching) versus temperature: D = α( T− α) b . The parameters of that equation were shown to vary in relation to the initial in situ temperature. The data suggested that the acclimation of females to ambient temperature might be transmitted to the maturing eggs before spawning.