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Arq. Bras. Med. Vet. Zootec. vol.55 no.3 Belo Horizonte June 2003
Parasitoids of flies collected in chicken viscera in Itumbiara, Goiás, Brazil
Parasitóides de moscas coletadas em vísceras de galinha em Itumbiara, Goiás
C.H. Marchiori; L.A. Pereira; O.M. Silva Filho; L.C.S. Ribeiro; V.R. Borges
Departamento de Ciências Naturais Instituto Luterano de Ensino Superior de Itumbiara-ILES-ULBRA Caixa Postal 23-T 75500-000 - Itumbiara, GO
Keywords: fly, urban area, biological control, natural enemy
Este estudo teve como objetivo determinar as espécies de parasitoides associados com moscas coletadas em vísceras de galinha, em Itumbiara, Goiás. Armadilhas contendo vísceras de galinha como isca foram utilizadas para atrair a moscas. As pupas, obtidas pelo método de flutuação, foram colocadas individualmente em cápsulas de gelatina (nº 00) e mantidas em laboratório até a emergência das moscas e/ou dos parasitoides. A prevalência total de parasitismo foi de 20,0%. Brachymeria podagrica, Hemencyrtus sp. (Hymenoptera: Encyrtidae), Nasonia vitripennis (Hymenoptera: Pteromalidae), Paraganaspis egeria (Díaz, Gallardo & Wash) (Hymenoptera: Figitidae), apresentaram prevalência de parasitismo de 8,9%, 10,8%, 0,9% e 0,3%, respectivamente.
Palavras-chave: mosca, área urbana, controle biológico, inimigo natural
Diptera is an optimal model for the study of synanthropy, not only because of its ecological importance, but also because of its medical-veterinary aspects, particularly vectors of etiological agents such as amoeba cysts, helminth eggs, pathogenic enterobacteria, viruses and fungi. Diptera is one of the largest order of insects, comprising abundant number of species as well as of individuals. Besides, these dipterous are of great medical and veterinary importance since they may produce myiases and may be vectors of microorganisms pathogenic to man and animals (Greenberg, 1971).
A diverse fauna of parasitoids, which are responsible for the natural control of these dipterous, develops together with flies. Since parasitoids occupy a superior trophic level, they act as determining factors on the population densities of their hosts due to the diversity of their physiological and behavioral adaptations. As an alternative to control these insects, natural regulators can be used, such as parasitoids, that are the agents responsible for the reduction of the synanthropic fly populations (Mendes, Linhares, 1993).
The objective of this study was to identify species of parasitoids in chicken viscera in Itumbiara County.
The study was developed in Itumbiara County, State of Goias (18º25´S;49º13´W), Brazil. Flies were attracted to traps made with 19x9cm opaque dark cans with two blinders-like openings, located in the inferior third part to allow flies entry. Nylon funnels were coupled in the upper part of the cans, opened at the ends, with bases pointing down and wrapped with plastic bags, enabling the collection of flies and parasitoids. Chicken viscera were used as baits inside the cans, over a layer of sand. Five traps, hanging on eucalyptus trees one meter above the ground were disposed two meters apart from each other and 50 meters from domestic garbage cans. The insects collected were taken to the laboratory, killed with ethyl ether and kept in 70% ethanol for further identification. The contents of the traps were placed in plastic containers having a layer of sand to be used as a substratum for larvae to pupate. The sand was sifted after 15 days and pupae were extracted and placed individually in gelatin capsules (number 00) to obtain flies and/or parasitoids.
The prevalence of parasitism was calculated by the following formula: P=(parasitized pupae/total of pupae) x100 (Margolis et al., 1982; Bush et al., 1997). Chicken viscera exposure time preference by flies was tested by the chi-square test, at 5% probability.
During the period of March 2001 to March 2002, 695 pupae of Diptera and 145 specimens of parasitoid were collected. The overall prevalence of parasitism was 20.0%. The high prevalence of parasitism can also be related to the collections of gregarious parasitoids.
Among the Diptera, Peckia chrysostoma (Wiedemann) (Diptera: Sarcophagidae) were the most abundant, comprising 40.3% of the sampled insects; the second most abundant species was Poecilosomella sp. (Diptera: Sphaeroceridae) with 24.7% (Tab.1). P. chrysostoma, a neotropic and synantropic species, is widely spread and frequently found at high densities in Rio de Janeiro (D'Almeida, 1984).
From the hosts collected, the importance of the species Chrysomya albiceps (Wiedennam) (Diptera: Calliphoridae) and Musca domestica L. (Diptera: Muscidae) must be pointed must. Chrysomya albiceps has a great medical and sanitary importance, because it is responsible for secondary myiases and for being vector of pathogenic microorganisms. Concerning M. domestica, it is a species of great health interest, due to its synantropic characteristic, its abundance in urban areas, capacity of development in several sorts of substrates, and its high reproductive capacity (Greenberg, 1971; Marchenko, 1985; D'Almeida, 1986).
Hemencyrtus sp. (Hymenoptera: Encrytidae), followed by Brachymeria podagrica (Fabricius) (Chalcididae) (42.8%), were the most frequent species (52.0%) of the collected parasitoids (Tab. 1). Hemencyrtus sp. occurs worldwide and lives associated to Diptera, emerging from their pupa shells (Noyes, 1980). As for other species of Diptera, P. chrysostoma presented a higher diversity of parasitoids (three).
Brachymeria podagrica, Hemencyrtus sp., Nasonia vitripennis (Hymenoptera: Pteromalidae), Paraganaspis egeria (Díaz, Gallardo & Wash) (Hymenoptera: Figitidae), presented a parasitism prevalence of 8.9%, 10.8%, 0.9% and 0.3%, respectively.
A great number of individuals were obtained from the host Hemilucilia flavifacies Enderlein (Diptera: Calliphoridae) (Table 2). The high prevalence can also be related to the collections of gregarious parasitoids. Hemencyrtus sp. behaved as gregarious, with several individuals emerging from the same pupary.
The parasitoids collected showed preferences for the following flies: B. podagrica preferred C. albiceps and P. chrysostoma; Hemencyrtus sp. preferred Hemilucilia flavifacies Enderlein (Diptera: Calliphoridae) and P. chrysostoma; and N. vitripennis preferred M. domestica (l 2=149.7; DF=15; P<0.0001).
The use of chemical compounds to control flies may cause damages to the environment as well to human health. The search for effective natural enemies may be a viable alternative to submit these vectors to a control program.
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Recebido para publicação em 9 de maio de 2002
Recebido para publicação, após modificações, em 28 de novembro de 2002
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