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 succes s when males were fed the dinoflagellates Prorocentrum micans, Lingulodiniu m polyedra and Gymnodinium sanguinium was not due to visible ultrastructura l anomalies of the spermatozoa. The cellular organization of the sterile sp ermatozoa was comparable to reproductive cells produced by wild males or by males fed the dinoflagellate Prorocentrum minimum which induced high hatch ing success. The gonads of T. stylifera females fed the diatoms Thalassiosi ra rotula and Phaeodactylum tricornutum also appeared normal at the ultrast ructural level and comparable to wild females. The fatty acid compositions of the dinoflagellates P. micans and P. minimum were similar, suggesting th at the negative effects of three of the dinoflagellates on male fertilizati on 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 suc cess induced by these diatoms was not due to a fatty acid deficiency in the diet. Both algae contained sufficient amounts of polyunsaturated fatty aci ds (eicosapentaenoic and docosahexaenoic acids), generally considered essen tial during development.