Chapter V-4 - Fungi: Oomycetes and chytridiomycetes

Abstract

This chapter discusses isolation, culture, and production of Oomycetes and Chytridiomycetes. Aquatic fungi, formerly grouped together as Phycomycetes, are a diverse group of organisms characterized by a motile, flagellated zoospore at some stage of their life-cycle. Chytridiomycetes are characterized by the production of posteriorly uniflagellate zoospores. Isolation of mosquito parasitic organisms from larval breeding habitats is facilitated by the use of sentinel cages. The only option for culturing Coelomomyces spp. is in vivo cycling between its two hosts. Lagenidium giganteum can either be maintained in vivo or it can be isolated from infected larvae on agar media. Zoosporogenesis by L. giganteum is induced by nutrient deprivation. Quantification of zoosporogenesis is relatively easy in the laboratory as long as field water is not being used. Zoospores, which lack a cell wall, are too fragile to be applied in natural habitats and therefore, concentrated preparations of either mycelia or oospores are applied, with sporulation subsequently induced by dilution in the larval breeding habitat. The main advantage of using L. giganteum for operational mosquito control is its ability to recycle at appreciable levels for weeks, months or even years following a single field application.