Copepod recruitment and food composition: do diatoms affect hatching success?

Laboratory experiments were conducted to differentiate between factors controlling the hatching success of copepod eggs. Factors that could affect viability of eggs; viz food quality, female condition and external factors were investigated. In a series of experiments the copepod Acartia tonsa Dana was fed several different diets while egg production and hatching success were monitored. The diet was analysed for fatty acid content as an indicator of food quality. Both egg production and hatching were found to be affected by the nutritional quality of the food. Hatching was also highly dependent on female fertility. External effects were tested by exposing eggs to diatom extracts. Negative effects were only evident at high extract concentrations, but disappeared when aeration was supplied to the solution. Oxygen measurements showed that failure to hatch was due to hypoxia in the extracts. No inhibitory or toxic effects of diatom cell components on hatching could be found.