John Paul Kramer

Susceptibility of sixteen species of Diptera to the fungal pathogenEntomophthora muscae (Zygomycetes: Entomophthoraceae)

Sixteen species of Diptera from eight families were inoculated with conidia ofEntomophthora muscae (Zygomycetes: Entomophthorales). The following species were susceptible and became infected at the rates indicated:Musca domestica (100%),Sarcophaga haemorrhoidalis (86%),Phaenicia sericata (44%),Scatophaga stercoraria (30%),Drosophila melanogaster (11%),Aedes aegypti (3%), andStomoxys calcitrans (2%). The following species were not susceptible under the conditions of this study:Phormia regina, Calliphora vicina, Rhagoletis pomonella, Eristalis arbustorum, Eristalis tenax, Toxomerus geminatus, Sphaerophoria scripta, Syrphus sp. andAllograpta oblique. Differences in susceptibility were not related to the taxonomic affinities of the taxa tested; however, susceptibility may be related to interspecific morphological differences of hosts, such as, scales and hairs on the host or the degree of sclerotization of host integument.Each host-pathogen interaction was examined. Characteristics of the post-mortem growth of the fungus were similar within a host species but differed between host species. These differences in post-mortem growth of the fungus were related to the suitability of host species as a substrate for the pathogen. The incubation period of the mycosis was related to host species and not to host size, it varied from seven days for the relatively largeS. haemorrhoidalis to 17 days for the relatively smallA. aegypti.

Culture of Entomophthora muscae in vivo and its infectivity for six species of muscoid flies

A method for the continuous culture of Entomophthora muscae (Entomophthoraceae) in adult house flies (Musca domestica) is described. Using this method we have maintained the host-pathogen system in the laboratory for more than one year. The ability of this isolate to cause fatal infections in virtually all of the house flies at risk has remained constant. The face fly (Musca autumnalis), the onion fly (Hylemya antiqua), and the seed-corn fly (H. platura) are susceptible to this isolate. The stable fly (Stomoxys calcitrans), the black blow fly (Phormia regina), and the false stable fly (Muscina stabulans) are not.

The Extra-Corporeal Ecology of Microsporidia

The two environments of microsporidians are: (i) the intra-corporeal, formed by the tissues of the host in which these parasites grow and multiply; and (ii) the extra-corporeal, formed by all that surrounds these tissues. Whereas these two environments are intimately related and at times inseparable, I have attempted to separate them for the purpose of discussion. It would not be profitable nor even practicable to attempt to catalog all the known information that treats some aspect of the extra-corporeal ecology of microsporidians. Therefore, I have attempted to present a cohesive overview of the subject with some examples that illustrate specific points. To provide the reader with a sense of continuity, the discussion first centers around the process of dissemination and this is followed by a commentary on other facets of microsporidian life in the extra-corporeal environment. Recent reviews that relate in part to the topic at hand are those by Canning (1970) and Maddox (1973). Reviews by Putz and McLaughlin (1970) and Sindermann (1970) also contain some information that bears upon the extra-corporeal experience of spores.

Entomophthora culicis (Zygomycetes, Entomophthorales) as a pathogen of adult Aedes aegypti (Diptera, Culicidae).

Abstract The infectivity of Entomophthora culicis for adult Aedes aegypti was demonstrated for the first time. Conidia from field‐collected Chironomus decorus were highly infective for Aedes aegypti while those from several other species of midges were not. Conidia from experimentally infected A. aegypti and from yolk cultures were equally infective for other test A, aegypti. The results suggest that the incubation period of the disease ranges from 5 to 7 days but may extend to 10 days on occasion. Mortalities of 100% by Post‐Exposure Day 10 were observed in five small groups of adults subjected to conidial showers.

Effect of ultraviolet radiation on the microsporidian Octosporea muscaedomesticae with reference to protectants provided by the host Phormia regina.

Abstract The effect of ultraviolet light on the microsporidian Octosporea muscaedomesticae in relation to infection in the adult black blowfly, Phormia regina, was investigated. A 30-Watt germicidal lamp, 253.7-nm wavelength, was used as source of uv light in five investigations. In addition, sunlight served as a uv source in two studies. Viable naked dried spores exposed to the uv lamp at a distance of 10 cm were killed after 15 min. Viable naked spores in an aqueous suspension were killed after 30 min of exposure to the uv lamp and after 3 hr of exposure to bright sunlight, respectively. Daily 30-min uv lamp exposures on living hosts harboring all life phases of the parasite did not interfere with the ensuing infection in the blowflys midgut and the pathogens developmental cycle. Spores harvested from uv-treated infected hosts were found to be as infective as spores retrieved from hosts not treated with uv. Spores contained in dried fecal droplets and exposed up to 3 hr to the uv lamp, or 12 hr to bright sunlight, respectively, remained infective. Addition of uric acid to a preparation of naked spores prior to 15- and 30-min uv irradiations yielded 100% infection in both host groups. A uv-protective function is ascribed to components provided by the hosts tissues and feces.

Differential germination among spores of the microsporidian Octosporea muscaedomesticae

SummaryBy monitoring the changes in a population of O. muscaedomesticae spores as it passed through the alimentary tracts of adult Phormia regina it was found that most spores germinate during the first passage while others do not germinate until they have made 2, 3, or 4 passages. Possible explanations for these differences are suggested.

A mycosis of the blood-sucking snipe fly symphoromyia hirta caused by Erynia ithacensis sp.n. (Entomophthoraceae)

A mycosis was detected in Symphoromyia hirta (Diptera: Rhagionidae) collected near Ithaca, New York. Other dipterous victims of the disease included Rhagio mystaceus and Empis obesa. Afflicted flies, found on the under surfaces of leaves of woody plants, were affixed to the substrate by rhizoids. The pathogen formed both resting spores and conidia on the exterior of the cadavers. It grew rapidly and sporulated abundantly in culture. Attempts to induce infections in Musca domestica and Aedes aegypti were unsuccessful. The pathogen Erynia ithacensis sp. n. forms resting spores that are incised with very irregular ridges. This characteristic serves to separate it from other dipterophilic species of Erynia.

Dosage effect study of the microsporidian Octosporea muscaedomesticae in the adult black blowfly Phormia regina, with reference to the reproductive cycle of the pathogen.

Abstract The quantitative pathogenicity of the microsporidian Octosporea muscaedomesticae in adult Phormia regina was studied. Dosage levels ranging from 10 2 to 10 6 spores per fly were administered to five and six groups of newly emerged, starved adult flies in two trials. Rates of mortality and infection were determined. A direct relationship between number of spores ingested and subsequent infection rate was found in a 4-day trial while no such relationship was found in an 18-day trial, using the same source of inoculum and host flies from the same colony. The lack of a direct relationship between spore dose and rate of infection in the 18-day trial is explained on the basis of the short spore-to-spore development time of the parasite. New generations of spores formed within the host tissues obscure the results in relation to the spore dose initially administered. An appreciable number of spores in the inoculum is needed to initiate frank infection. The ID 50 (median infective dose) was 4.4 × 10 4 spores per fly after 4 days.

An octosporeosis of the black blowfly, Phormia regina: Incidence rates of host and parasite

SummaryAdult black blowflies Phormia regina were trapped from April through October in Urbana, Illinois for the years 1963 and 1964. Samples of flies from each catch were examined for the presence of the microsporidian parasite Octosporea muscaedomesticae. In 1963, the monthly parasite incidence rate steadily increased with the progression of the seasons while the fly population declined over the same period. In 1964, the monthly parasite incidence rate followed no decernable pattern; this was probably attributable to the fact that the host remained comparatively scarce for the entire period following heavy spring rains. The observed monthly parasite incidence rates ranged from zero to 13% over the two-year period. The annual parasite incidence rate was 4% in 1963 and 4.5% in 1964. No significant differences were found in the parasite incidence rates of females versus males. The observed parasite incidence rates, while indicative of general trends, probably are lower than the actual rates in nature. Reasons for this are discussed. Finally it is suggested that O. muscaedomesticae may at times act as a suppressor of P. regina populations in the field.ZusammenfassungErwachsene Fliegen der Art Phormia regina wurden vom April bis Oktober in Urbana, Illinois, in den Jahren 1963 und 1964 gefangen. Einige Fliegen aus jedem Fang wurden auf Microsporidien der Art Octosporea muscaedomesticae untersucht. Im Jahre 1963 erhöhte sich die monatliche Infektionsrate ständig mit dem Fortschreiten des Jahres, während sich die Fliegenpopulation in derselben Periode verminderte. Im Jahre 1964 war eine solche Beziehung nicht erkennbar; dieser Umstand wird darauf zurückgeführt, daß der Wirt während der ganzen folgenden Periode der schweren Frühlingsregenfälle relativ spärlich auftrat. Die beobachtete monatliche Parasitenhäufigkeit wechselte während der 2-Jahresperiode zwischen 0 und 13%. Die jährliche Parasitenhäufigkeit lag 1963 bei 4% und im Jahre 1964 bei 4,5%. Es war keine significante Differenz in der Parasitenhäufigkeit zwischen weiblichen und männlichen Tieren festzustellen. Die beobachtete Parasitenhäufigkeit war, wenn man den generellen Trend betrachtet, wahrscheinlich eher geringer als die aktuelle Rate in der freien Natur. Die Gründe für diese Umstände werden diskutiert. Schließlich wird angenommen, daß sich O. muscaedomesticae als ein begrenzender Faktor („supressor“) für P. regina Population in der freien Natur anzusehen ist.

Octosporea carloschagasi n.sp., a microsporidian associate of Trypanosoma cruzi in Panstrongylus megistus.

SummarySome protozoan forms from Panstrongylus megistus that Chagas had incorporated into his original description of Trypanosoma cruzi are compared with schizogonic and sporogonic stages of the microsporidian Octosporea muscaedomesticae. On the basis of the evidence presented O. carloschagasi n. sp. is described.