Egg production in the copepod Acartia tonsa was evaluated using different densities of the microalgae Thalassiosira weissflogii, Chaetoceros muelleri and Isochrysis galbana. Male and female were kept under controlled conditions (salinity 30, 20 • C, photoperiod 12L:12D), acclimated to the experimental conditions and left over a period of 24 h to allow copulation. Algal densities tested were equivalent in biovolume and corresponded to 0, 2.5, 5, 10, 20, 40 and 60.10 3 cells.mL −1 of T. weissflogii. Ten acclimated female were separated, transferred to glass bottles and exposed for further 24 h to the corresponding experimental medium. After this period, the eggs were fixed and counted. Copepod egg production reached a threshold value when T. weissflogii, C. muelleri and I. galbana were supplied at 10.10 3 , 140.10 3 and 640.10 3 cells.mL −1 , respectively. Mean egg production corresponded to 28.0 ± 0.5, 20.1 ± 1.0 and 22.0 ± 3.5 eggs.female −1 .day −1 , respectively. Copepods fed T. weissflogii showed the highest mean egg production while those fed I. galbana reached a maximum egg production when the algae were supplied at a density two-to fourfold higher, considering the biovolume of T. weissflogii and C. muelleri. These differences are explained considering the different sizes of the microalgae used to feed the copepods.

In this study the effects of different salinities and algal diets on number of eggs produced by the copepods Pseudodiaptomus richardi and Notodiaptomus incompositus, were evaluated under controlled laboratory conditions. For P. richardi the development time from newly hatched nauplii to adults was compared for the three salinities under saturating food conditions. This species showed to be very tolerant to a wide range of salinities presenting the same growth rate from nauplii to adults when reared at salinities (S) 5, 15 and 30. The survivorship was 40,51 ± 7,6% in average, with a maximum of 49% at S = 15. The mean development time was 16 days (20°C), with no differences (ANOVA, p > 0,05) among the three salinities tested. The egg production values where in average higher (p < 0,05) for females reared at tested salinity since nauplii stages, when compared to acclimated females captured from the natural environment. The copepod N. incompositus showed oligohaline characteristics since adults of this species presented total mortality at S = 15. The survivorship increased with the decrease of salinity, being 20% at S = 10 and 79% at S = 1. There was no clutch production of N. incompositus at S = 10, whereas it was very low at salinities 5 and 1. Regarding the diets tested there was no significant differences (ANOVA, p > 0.05) among the algae evaluated (Isochrysis galbana, Thalassiosira weissflogii, Chaetoceros muelleri and mixed diet). However the number of eggs produced found for P. richardi were in average twelve times higher than those observed for N. incompositus. The results of this study indicate that P. richardi is a very tolerant species, being well adapted for the constant fluctuating conditions of salinity and food composition usually found in estuaries and coastal areas.

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