Etude des variations du poids sec et de la constitution chimique élémentaire de Tisbe holothuriae (Copepoda: Harpacticoïda) élevé sur différents régimes artificiels

Dry weight and body composition of C, H and N were investigated in male and female Tisbe holothuriae Humes fed 7 artificial compound diets and a living algal diet (Nannochloris sp.) over the whole biological cycle. No correlation was found between the respective proportion of C, H and N in the food and in the copepod body. Food quality had a significant effect on dry weight. Carbon content varied between 35.35 and 42.32% of body dry weight in females, and between 25.10 and 26.84% in males. Nitrogen values were 9.11 to 10.00% and 6.79 to 6.99%, respectively, varying with different diets. The C:N ratio varied between 3.74 and 4.28 in females and between 3.70 and 3.87 in males. Some diets had a significant effect on this ratio. In some experiments, three different temperatures were tested using the same diet. Body dry weight was inversely correlated with temperature, but no clear relation appeared between C:N and temperature. C:N variations were directly related to C concentration and seemed independent of N concentration. It is suggested that C variations correspond to different levels in lipid content under different trophic conditions. The relation between elementary chemical composition and fecundity in T. holothuriae fed different diets is discussed.