CHEMICAL-COMPOSITION OF LEPTOCYTHERE-PSAMMOPHILA (CRUSTACEA, OSTRACODA) AS INFLUENCED BY WINTER METABOLISM AND SUMMER SUPPLIES

Leptocythere psammophila is well known for the ecophenotypic variation s of the ornamentation of its carapace. To test the respective influen ces of the environmental parameters on its ornamentation, 41 living sp ecimens were collected in the Baltic Sea, the North Sea and in the Eng lish Channel during spring, summer and winter (April 1987, September a nd December 1988). The carbonate carapaces of these specimens were ana lyzed by means of electron microprobe. Thirteen elements were detected . Statistical comparisons of means and variances were performed using classical F and t-tests. Data were submitted to Normalized Principal C omponent Analysis and Discriminant Analysis. There are no significant differences between chemical composition of the carapaces from the dif ferent stations. However, the variability of Baltic Sea specimens is l ower than that of other stations. Nonetheless, strong and significant differences appear when samples are gathered by season. The chemical c omposition of summer individuals is controlled by variations in water salinity and in fine grain terrigenous sediment supply. The compositio n of winter samples is related to the incorporation of Mg. In the case of spring specimens, both these factors have to be considered. Discri minant analysis between winter and non-winter samples sets correctly 8 4% of the individuals. The wrongly classified specimens are interprete d as ostracods that did not molt during the season of sampling. By att ributing them to their possible season of molting, the result of the N ormalized Principal Component Analysis improves. Differences in orname ntation are slight. They occur between the samples from the Baltic Sea and those from the other stations. The former have larger and less nu merous punctations and lack the smooth surface in the anteroventral pa rt of the carapace. The punctation diameter is more variable during su mmer than during spring. In the range of environments investigated, or namentation of the carapace of L. psammophila seems unaffected by the seasonal environmental variations whereas its composition exhibits str ong differences.