The role of protists in the diet of larval container mosquitoes

Mosquito larvae feed on a variety of food types, although most research examining larval nutrition has focused on bacteria and particulate organic matter.  However, fungi and bacteria, although important for nitrogen and lipids, may be insufficient in terms of carbon that may be supplied by protists.  Thus, we predicted that protists would have a positive additive effect on larval performance as compared to a single food type.  We conducted a laboratory experiment where larval survival, adult mass, and larval development time of two species of mosquitoes (Culex coronator and Aedes albopictus) was compared under two food environments, bacteria alone and bacteria with protists.  Water was collected from discarded tires and served as a source of microorganisms.  The water in microcosms was re-sieved every 3-6 days and a Lactalbumin-yeast mixture was added to each cup every 5 days.  Analyses of survival resulted in an effect of species and treatment but not their interaction. Specifically, Ae. albopictus exhibited significantly higher survival compared to Cx. coronator regardless of treatment, and contrary to predictions the bacteria alone treatment produced higher survival compared to bacteria and protists.  Development time did not vary under different food treatments for Ae. albopictus, however Cx. coronator developed approximately two days faster with both protists and bacteria compared to bacteria alone.  Thus, the benefit of protists appears to be species dependant and may have variable effects on life history parameters. An additional study will test differences in larval longevity between the treatment levels in the absence of other food sources.