Effect of specific dinoflagellate and diatom diets on gamete ultrastructure and fatty acid profiles of the copepod Temora stylifera

The ultrastructure of Temora stylifera male and female gonads was examined in individuals fed three dinoflagellate and two diatom species which affect copepod hatching success. The results showed that low fertilization success when males were fed the dinoflagellates Prorocentrum micans, Lingulodinium polyedra and Gymnodinium sanguinium was not due to visible ultrastructural anomalies of the spermatozoa. The cellular organization of the sterile spermatozoa was comparable to reproductive cells produced by wild males or by males fed the dinoflagellate Prorocentrum minimum which induced high hatching success. The gonads of T. stylifera females fed the diatoms Thalassiosira rotula and Phaeodactylum tricornutum also appeared normal at the ultrastructural level and comparable to wild females. The fatty acid compositions of the dinoflagellates P. micans and P. minimum were similar, suggesting that the negative effects of three of the dinoflagellates on male fertilization capacity was not related to a lack of any fatty acid. Lipid profiles of the diatoms T. rotula and P. tricornutum also suggest that low hatching success induced by these diatoms was not due to a fatty acid deficiency in the diet. Both algae contained sufficient amounts of polyunsaturated fatty acids (eicosapentaenoic and docosahexaenoic acids), generally considered essential during development.