EGG-PRODUCTION AND THE NUTRITIONAL ENVIRONMENT OF ACARTIA-TONSA - THEROLE OF FOOD QUALITY IN COPEPOD NUTRITION

The hypotheses that (1) the egg production (EP) of Acartia tonsa is en hanced by dietary diversity because, (2) dietary diversity increases t he probability that a nutritionally complete diet will be obtained, we re tested. A. tonsa was provided with a diatom, an approximately equiv alent sized dinoflagellate, and a mixture of the two foods. EP, hatchi ng success CH) and gross egg production efficiency varied as diatom < dinoflagellate < mixture. EP and H were then measured with diets consi sting of Isochrysis galbana (= Iso, an alga), or Debariamyces hanseni (= Deb, a yeast), or Oxyrrhis marina (a heterotrophic dinoflagellate) cultured on either Iso or Deb. EP and H were also determined when each kind of O. marina culture was supplemented with Iso. Fatty acid and a mino acid analyses indicated that the two O. marina cultures represent ed two nutritionally different food items. EP in the Iso, Deb and Iso- fed Oxyrrhis groups was low. In Deb-fed Oxyrrhis and Iso-supplemented groups, EP was high. H was > 60% in Iso-supplemented, yeast-fed O. mar ina group and <30% in all others. (C) 1995 International Council for t he Exploration of the Sea