Aspectos da Biologia de Tachinaephagus Zealandicus Ashmead (Hymenoptera:Encyrtidae), parasitoide de larvas de dipteros sinantropicos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

Tachinaephagus zealandicus Ashmead is a gregarious endoparasitoid that attacks third instars of muscoid flies in the Southem Hemisphere. The purpose of the present study was to evaluate the influence of six constant temperatures (16, 18, 20, 22, 25 and 27°C) on development time, the influence of emergence order on longevity, and the effects of temperature and food treatment on longevity, the influence of nutritional treatment, host density and temperature on attack rates on T. zealandicus and also evaluated the influence of four constant temperatures (15, 20, 25, 30° C) on development time and 10ngevity of microsporidium-infected and uninfected colonies. Emergence success was greatest at 22°C for both males and females; significantly fewer (24.1-30.4%) parasitoids emerged at 16°C and 25°C compared with 22°C. Development time ranged fiom 24.0 to 56.9 days for both sexes. No emergence was observed at 27°C. Early-emerging parasitoids had greater longevity than parasitoids that emerged later fiom the same cohorts. The longevity of females given honey and water decreased with increasing temperature, and those reared at 16°C lived about three times longer than those kept at 27°C. Females given honey and water had similar longevities at 16-20°C, and females that were given only water lived for only 4.8-7.6 days at all temperatures. Females lived significantly longer overall than males at alI temperatures except 16°C, but differences due to sex were small compared to the effects of temperature and nutrition. Nutritional treatment (honey, honey+water, water, and starvation) had statistically significant effects on rates of attack on C. puloria andM domestica, however no significant treatment effects were observed in rates of progeny production. With both M domestica and C. puloria it was observed that the percentage of killed hosts decreased as host density increased. Temperature had significant effects on host attacks on C. puloria. During 24 hours of ex-posure, highest rates ofhost attacks were observed at 22°C. For the number ofkilled hosts, differences were not statistically significant among 20, 22, 25 and 27°C. An undetermined microsporidium was found infecting Tachinaephagus zealandicus, a gregarious parasitoid that attacks third instar larvae of muscoid flies. Spores were present in alI body regions and in all stages of development. Infected adults contain an average of 3.75 x 105 spores. ln order to separate the colony into infected and uninfected individuais, we treated infected females on rifampicin mixed with honey as food and after 8 days ca. 37% of individuais of progeny examined were still infected. An uninfected culture was established and the two colonies were tested for infection transmission. lt was observed that the efficiency of maternal transmission was 96.3%. lnfected parasitoids developed significantly faster than uninfected ones at 15, 20 and 25°C. Uneclosed puparia were dissected and the results showed that infected parasitoids had difficulty emerging fiom host puparia, especially at 20 and 25°C. The longevity of females decreased as temperatures increased Effects of infection on longevity were strongest at alI temperatures among parasitoids that were given honey and water; longevity was short in alI parasitoid groups that were only given water. ANOV A results showed that not only temperature and feeding treatment but also the infection affected significantly the longe"ity of females and males. Females and females fiom a colony infected with the undetennined microsporidium had similar lifespans (3.7-3.9 days) when parasitoids were provided with honey, water and house fly larvae continously after emergence. Infected parasitoids produced significant1y fewer progeny than uninfected parasitoids, and a greater proportion of infected parasitoid progeny failed to emerge from host puparia. Most host attacks and parasitism occurred on the first day of emergence, and little parasitism was observed by day 3 after emergence for both uninfected and infected females, indicating that this is a proovigenic species that emerges with a predetermined number of oocytes that are deposited when hosts are available for parasitism. Comparison of host attacks and parasitism on two species of flies (house flies and Sarcophaga bullata (Diptera: Sarcophagidae) indicated that the effects of infectÍon are modulated by the species of host present. Similar numbers of both species fly hosts were killed by uninfected and infected parasitoids (70.2-74.1 hosts attacked per group of 5 female T zealandicus). However, infected parasitoids produced substantially fewer progeny from house fly hosts (311.1 for uninfected parasitoids compared with 138.3 progeny from infected parasitoids), wheras infection had no significant effect on progeny production from the much larger S. bullata hosts (588.2 and 460.1 progeny produced by uninfected and infected parasitoids, respectively). Differences in performance on the two host species may be due to innate differences in host quality or to the pronouced size differences of the two species (190 mgllarva for S. bullata versus 20 mgllarva for M domestica). Uninfected T zealandicus that were stored at 15°C had highest rates ofhost attacks (58-62 hots killed per group offive female parasitoids at 25°C) and progeny production 173.8-261.2 progeny) after 6-12 days of storage at this temperature; relatively few hosts were attacked or parasitized after O or 1 day at 15°C

ASSUNTO(S)

temperatura longevidade fecundidade densidade

ACESSO AO ARTIGO

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