The influence of microbial food sources and aeration on the growth of Ceriodaphnia quadrangula (O.F.Müller) (Crustacea: Cladocera) under experimental conditions

Casual observations had shown that, in laboratory cultures, populations of Ceriodaphnia quadrangula (O. F. Muller) rarely persisted for more than a month at most. It is shown here that populations of C. quadrangula can be maintained in static water on a diet of mixed algae (mainly Scenedesmus quadricauda (Turp.) Brev., but if the water is disturbed by a slow current of ascending air bubbles, the numbers of C. quadrangula decline. Death is not, however, immediate, and at high densities populations may persist in disturbed water for several weeks before numbers start to decline. Numbers of C. quadrangula did not decline in disturbed water when the food was changed from the alga Scenedesmus to the animal Artemia salina (L.). Individuals of C. quadrangula in the presence of decomposing naupliar larvae of A. salina grew as well in disturbed as in static water and in static water their numbers increased at a greater rate on this animal diet than on an algal diet of Scenedesmus. When the bacterial populations associated with Scenedesmus were greatly reduced, there was no increase in the numbers of C. quandrangula. Microbes associated with Scenedesmus, and not the alga per se, seem to be used as food by C. quandrangula.