Effects of Diatom on the Reproduction of Copepod Oithona similis

Under laboratory conditions, potential influence of diatom diets on reproduction of zooplankton Oithona similis was studied. In period of 17-day laboratory experiments. The diets were analyzed for fatty acid content as an indicator of food quality. The results showed that the female survival rates of all treatments were kept more than 80% except Phaeodactylum tricornutum. Comparing to the initial value, egg production of Oithona similis was reduced in diatom diets (Phaeodactylum tricornutum, Nitzschia pungens), but remained in normal level in Skeletonema costatum and MIX, indicating that some single diatom diets had negative effect on the egg production of Oithona similis. However, this negative effect can be eliminated by feeding with mixed food. Among all the treatments, hatching success in filtered seawater were significantly higher than those in algal exudates, indicating that not only diatom but also other phytoplankton in certain concentration can release extracelluar substance that may inhibits egg from hatching.