Reproduction and growth of Euterpina acutifrons (Copepoda: Harpacticoida) under experimental conditions

Abstract

Individual specimens of Euterpina acutifrons (Copepoda: Harpacticoida) taken from the mass cultures of the C.N.E.N.-EURATOM Laboratory at Fiascherino, Italy, were reared in new culture media prepared with suspensions of several species of algae in filtered and sterilized sea water. All the experiments were carried out at a temperature of 18°C±1 C°. The influence of food concentrations on adult life-span and reproductive activity of E. acutifrons was analyzed. A good correlation was found between concentration of algal suspension and egg production. Maximum life-span was observed at intermediate values of food concentration. Other experiments were carried out to determine egg fertility and duration of the various embryonic and postembryonic development stages. Embryonic development time was calculated as approximately 2 days; the adult females appeared 10 to 12 days after hatching of Nauplius I. Production of nauplii by 6 females reared under conditions of excess food supply was also studied. These conditions were achieved by supplying high concentrations of a mixture of 4 different algal species and by completely renewing the culture medium at frequent intervals. Under these conditions, each female laid an average of 12.5 sacs and produced an average of 294.3 nauplii. An average production of 355.5 eggs per female was estimated. An analysis was made of growth in size and weight of the females: the average daily egg production in terms of dry weight corresponded to about 32% of the biomass of the adult female. Birch's (1948) method was used to calculate net reproduction rate (Ro=70.89), intrinsic rate of increase (rm=0.161) and mean generation time (T=26.5 days).