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Fig. 8. Calanus helgolandicus (crustacean). (A) Post-ingestion effect of the noxious diatom Thalassiosira rotula, provided to spawning females. Dose-dependent values (mean ± S.D.) of the hatching success are the results of triplicate observations for each diet treatment in batch samples of 30-100 eggs each. The control diet (test number 1, with the dinoflagellate Prorocentrum minimum) does not contain any noxious unsaturated aldehydes. Values of the potential production of two dominant unsaturated aldehydes (2,4-octadienal and 2,4,7-decatrienal combined), measured as the mean aldehyde production (2 fmol cell^-1) of these major unsaturated aldehydes in a T. rotula initial culture (T. Wichard, S. Poulet and G. Pohnert, unpublished). Potential yields of these aldehydes are calculated in relation to the equivalent diatom cell concentrations in female diets (test numbers 2-5). (B) Micrographs of a normal embryo at the two-blastomere stage produced by females fed the dinoflagellate diet (1), blockage of cell division in abnormal embryos produced by females fed the diatom diet at >10³ cells ml^-1 (2), fluorescent micrograph of a similar abnormal embryo stained with Hoechst 33342, specific to DNA, showing two nuclei blocked in the egg matrix (3). (C) Fate of N1 stage naplius produced by females fed two different diets [1 and 2, dinoflagellate (10⁴ cells ml^-1); 3, toxic diatom (10⁴ cells ml^-1)], sampled on day 5 during an 8-day incubation period. Light micrograph of a normal larva (1). Fluorescent confocal micrographs of normal (2) and apoptotic (arrow) (3) larvae double-stained with FITC-Annexin V + propidium iodide. Size of eggs=172 ±4µm; size of larvae=208±10 µm. Scale bars in B and C apply to 1, 2 and 3.

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