Studies on the Microsporidium, Octosporea Muscaedomesticae in Two Species of Calypterate Diptera
Lanka, Saraswathi
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https://hdl.handle.net/2142/72504
Description
Title
Studies on the Microsporidium, Octosporea Muscaedomesticae in Two Species of Calypterate Diptera
Author(s)
Lanka, Saraswathi
Issue Date
1992
Doctoral Committee Chair(s)
Maddox, Joseph V.
Department of Study
Entomology
Discipline
Entomology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Entomology
Abstract
The microsporidium, Octosporea muscaedomesticae infects many species of calypterate flies. When isolated from S. bullata, P. regina, and A. obliqua, O. muscaedomesticae showed significant differences in shape and size of the spores. It is not known whether these differences represent different species or a single heterogeneous species. The major purpose of this study was to compare the morphological characteristics and life cycle of the pathogen isolated from the three hosts and its interactions with the larval and adult stages of S. bullata and P. regina in order to understand the role of pathogen, host, and environmental factors in the epizootiology of O. muscaedomesticae. Specifically, the following hypotheses were tested: (1) Isolates of O. muscaedomesticae are ecologically host specific and are seldom transmitted between different species of hosts in nature; (2) O. muscaedomesticae is a pathogen of adult stages and although it can infect larval flies, these infections are ecologically insignificant; (3) O. muscaedomesticae does not significantly affect the longevity and fecundity of the adult stages of the host species; (4) O. muscaedomesticae is transmitted from adult to adult flies and epizootics are influenced largely by adult fly density and the number of active feeding sites; (5) O. muscaedomesticae is not an important naturally occurring biological control agent of flies.
O. muscaedomesticae isolated from P. regina, S. bullata, and A. obliqua were ultrastructurally similar. However, spores isolated from P. regina, were significantly smaller than those isolated from S. bullata but the size of the spores depended on the host to which the pathogen was fed. O. muscaedomesticae spores isolated from P. regina, when passed through four generations of S. bullata, did not change their virulence to P. regina. Generation time of the pathogen was three days in P. regina and five days in S. bullata. There was no significant difference in the activity (indicated by an experimental maze) of infected and uninfected adult P. regina. Infected S. bullata adults were less active than uninfected adults. Infection had no effect on the fecundity of S. bullata but infection did significantly reduce the fecundity of P. regina. Horizontal transmission of O. muscaedomesticae in S. bullata was inversely proportional to the number of active feeding sites available, and directly proportional to the host density. These two factors did not affect transmission of O. muscaedomesticae in P. regina. Larval stages could be infected only by feeding high dosages of spores. Infected larvae died as larvae or emerged as healthy adults. For this reason, it is doubtful that larval stages play an important role in the epizootics of the disease in field populations of O. muscaedomesticae.
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