Efeitos da salinidade e dieta alimentar sobre os copépodes Pseudodiaptomus richardi e Notodiaptomus incompositus em estudos de laboratório

Abstract

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.