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Laboratory populations of Tisbe clodiensis have been studied to provide information on the action of temperature on the fitness of some genotypes. All the populations were started with virgin females and males of the three genotypes (pp, pP, PP) at f(p) = 0.2 in agreement with Hardy-Weinberg distribution. Three of them were maintained at I5°C. and sampled at intervals of about 30 days, during a period of 273 days. Other populations have been kept at 18°C. and sampled at shorter intervals. The frequency...
Two concentrations of the domestic detergent, 2 and 4 mg/l, and one of LAS, 0.8 mg/l, which corresponds roughly to the amount contained in 4 mg of the commercial powder, were tested. Males and females were put into test solutions immediately after having reached sexual maturity, and left there until the first egg sac appeared in females, that is for two to six days. Ovigerous females were then isolated in water without detergent and the number of nauplii produced by the first egg sac was counted....
Two populations of Tisbe bulbisetosa from brackish environments were examined, the first from the mouth of the port-entrance of Grado, the second from a more inward position, from the Scardovari embayment on the Po delta. Comparisons were made with a third population from Malamocco, in the lagoon of Venice, which was studied in a previous work. The three localities differed in terms of chemical and physical parameters, and in the composition of benthic communities. The mean nauplius to adult survival...
Genetic load in Tisbe (Copepoda, Harpacticoida). II. T. holothuriae and T. bulbisetosa from the lagoon of Venice. Two populations of Tisbe holothuriae coming from two lagoon localities different as to their environmental heterogeneity but similar in their environmental variability, have been examined. The first station is located near Alberoni at a distance of about 3 kilometers from the sea; the second one is toward the inner part, near Malamocco, at about 6 kilometers from the open sea. The benthic...
Two populations of Tisbe holothuriae, coming from marine (Banyuls-sur-mer) and brackish waters (Sigean), have been analyzed before and after progressive inbreeding. It has been shown that an increase of the homozygosity due to inbreeding determines in both populations a progressive depression of survival, fecundity, mean generation time and intrinsic rate of natural increase. The inbreeding depression is higher in the marine population. The concealed genetic variability, estimated on the basis of...
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