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CiliatesThese protists use simple or compound cilia for locomotion and feeding, have a cytostome ("cell mouth"), and have two types of nuclei, micro- and macronuclei. Sexual reproduction is by conjugation. Division is transverse rather than longitudinal (Tanada and Kaya, 1993). Most ciliate species are commensuals in digestive tracts of insects (especially termites and roaches). Only a few are pathogenic (Corliss and Coats, 1976). Most of the pathogenic species are in the family Tetrahymenidae. The hosts are typically mosquitoes and black flies, the larvae of which can be attacked in water. Pathogenic ciliates penetrate the host and multiply in the hemocoel, although other tissues may be invaded. The mode of entry is unknown for most ciliate species; the mouth, cuticle, and wounds have been hypothesized (and verified in a few species) to be entry points (Clark and Brandl, 1976; Washburn et al., 1988). The pathogens may utilize the host fat body tissues, in which case mortality rates are high. Ciliate disease is called ciliatoses. Biological Control: Because most ciliates are commensuals and because most pathogenic species do not cause fast, acute disease in their hosts, there has been little interest in using this group in biological control programs. However, some pathogenic species have been shown to be important natural enemies of some aquatic insect species, including mosquitoes. |
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