Submitted by (edna.saturno@ufrpe.br) on 2016-11-22T14:40:50Z No. of bitstreams: 1 Christian Sherley Araujo da Silva.pdf: 746244 bytes, checksum: 46bc29b14cc397ec58c00ff6566278b8 (MD5) / Made available in DSpace on 2016-11-22T14:40:50Z (GMT). No. of bitstreams: 1 Christian Sherley Araujo da Silva.pdf: 746244 bytes, checksum: 46bc29b14cc397ec58c00ff6566278b8 (MD5) Previous issue date: 2009-12-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Parasitoid dispersion and host location can be affected by abiotic and biotic factors related to the parasitoid and its host. Therefore, we investigated the effects of age, photoperiod, and parasitism of Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae) under different densities of Plutella xylostella (L.) (Lepidoptera: Plutellidae), in the laboratory, green house and field. Moreover, we investigated the effect of superparasitism on O. sokolowskii fitness, its dispersion ability in the field, and the effect of a multiple host plant systems on its parasitism capacity. Results showed that there was no effect of the light regime (light or darkness) on the parasitization; although parasitoid was more active after 3h of light exposure. Female parasitization activity was maintained up to the age of 20 days, but the offspring emerged per host decreased as wasps aged. Parasitism rate increased with parasitoid age up to 96 h and when wasps received a constant number of hosts daily in comparison with a random number (13.3 versus 8.9 larvae). In addition, the number of larvae parasitized increased with host density, varying from 1.7 to 10.4, in the laboratory, and from 0.61 to 7.0, in the field. In the green house,parasitism was higher in microparcels with higher host infestation, and with more exposition time to parasitization (24h: 52.4% and; 72h: 80.7%). Regarding the superparasitism, it increased thenumber and longevity of offspring produced per larva, but decreased offspring body size. However, developmental time and sex ratio of parasitoid offspring were not affected. Parasitoids were able to disperse and parasitize larvae at similar rates throughout the field up to 24m from the releasing point. Intercropping of cabbage with broccoli, Napa cabbage, cilantro and green onion did not negatively affect parasitism rates of O. sokolowskii. Then, results suggest that O. sokolowskii could be favored by superparasitism and have the potential to control P. xylostella under different densities, regardless of the cropping system. / A dispersão de parasitóides e a localização do hospedeiro podem ser influenciadas por fatores abióticos e bióticos inerentes ao parasitóide e ao seu hospedeiro. Portanto, investigou-se o efeito da idade, do fotoperíodo, e parasitismo de Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae) submetido a diferentes densidades de Plutella xylostella (L.) (Lepidoptera: Plutellidae), em laboratório, casa telada e campo. Além disso, o efeito do superparasitismo em lagartas no desempenho de O. sokolowskii, a sua capacidade de dispersão em campo, e o efeito do sistema de cultivo de brássicas na sua capacidade de parasitismo foram investigados. Resultados mostram que não houve efeito do regime de luz (luz ou escuro) na taxa de parasitismo; porém, parasitóides apresentaram maior atividade após 3h de exposição à luz. Fêmeas de O. sokolowskii parasitam até 20 dias de idade, mas com redução na progênie com a idade. Houve maior parasitismo até a idade de 96 h das fêmeas e ao receberem diariamente um número constante de lagartas comparado à disponibilidade randômica (13,3 versus 8,9 lagartas).Adicionalmente, o número de lagartas parasitadas aumentou com a densidade do hospedeiro variando de 1,7 a 10,4, em laboratório, e de 0,61 a 7,0, em campo. Em casa telada, um maior parasitismo foi observado em microparcelas com maiores infestações de lagartas, e com o tempode exposição das lagartas aos parasitóides (24h: 52,4% e; 72h: 80,7%). Com relação ao superparasitismo, este aumentou o número e a longevidade dos descendentes produzidos por lagarta, mas com redução do tamanho do corpo dos descendentes. No entanto, a duração do desenvolvimento e a razão sexual dos descendentes não foram afetadas. Com relação à dispersão, parasitóides se dispersaram e parasitaram lagartas em taxas semelhantes até 24m a partir do ponto de liberação, e o policultivo de repolho com brócolis, couve-chinesa, coentro e cebolinha não afetou o parasitismo de lagartas por O. sokolowskii. Assim, resultados demonstram que O. sokolowskii pode ser beneficiado pelo superparasitismo e tem potencial para controlar P. xylostella em diferentes densidades e independente do sistema de cultivo.

Les symbioses eucaryotes/micro-organismes constituent une importante source d’innovation évolutive et de diversité écologique. Ces associations sont très répandues chez les insectes, en particulier chez les insectes parasitoïdes (insectes parasites d’autres insectes) qui hébergent en particulier une grande diversité de virus transmis verticalement. Leurs effets directs sur les parasitoïdes ainsi que les effets indirects sur la structure des communautés sont à l’heure actuelle mal compris. Nous avons abordé ces questions au travers l’étude d’un virus héritable (LbFV) ayant la particularité de manipuler le comportement de superparasitisme de son hôte, l’hyménoptère parasitoïde de drosophiles Leptopilina boulardi. La mise au point d’un outil moléculaire diagnostic de l’infection nous a permis de montrer que ce virus, spécifique à L. boulardi, peut atteindre de fortes prévalences dans les populations d’hôtes. Nous avons également mis en évidence un effet de la présence du virus sur les interactions compétitives interspécifiques au sein de la communauté des parasitoïdes de drosophiles. L’approche intégrée de ce travail constitue une étape importante dans la connaissance du rôle des virus héritables sur l’écologie et l’évolution de leurs hôtes / Eukaryots/microorganisms symbiosis is an important source of evolutionary novelty and ecological diversification. These associations are widespread in insects, particularly in parasitoids (insects that parasitize other insects) where a broad diversity of vertically transmitted viruses are found. However, their direct and indirect effects on host community are poorly understood. In this thesis, we used a system involving a Drosophila parasitoid, Leptopilina boulardi and a heritable virus LbFV that manipulates the behaviour of the parasitoid by increasing its tendency to lay eggs in a host that is already parasitized (superparasitism). Using a viral molecular marker developed in this work, we showed very high prevalences of the virus in L. boulardi populations. Additionally, we found a strong effect of the virus on interspecific competition in the Drosophila parasitoid community. The integrative approach of this work is an important step in understanding the role of heritable viruses in parasitoid ecology and evolution

Conura torvina (Cresson) (Hymenoptera: Chalcididae) is a solitary pupal endoparasite of numerous insect species. In Brassica crops it acts as a parasite of Plutella xylostella (L.) (Lepidoptera: Plutellidae) and was found as a hyperparasite of Cotesia rubecula (Marshall) (Hymenoptera: Braconidae) and several other parasitoid species. Cotesia rubecula was introduced into Virginia in 1987 as a biological control agent for Pieris rapae (L.) (Lepidoptera: Pieridae), and because C. torvina was thought to have eliminated this population of C. rubecula, studies of C. torvina's reproductive biology and behavior were initiated. A study using plants laden with "trap hosts" to detect C. torvina activity in the spring indicated no activity until late June, but proved trap host sampling to be an efficient and effective method of monitoring C. torvina activity. Studies of C. torvina's ability to reproduce in C. rubecula pupae of different ages indicated that C. torvina can successfully parasitize pupae at all stages of development, but was most successful in young to middle aged pupae. Studies of C. torvina's host species preference indicated the larger host species such as P. xylostella were preferred. Equal numbers of P. xylostella and C. rubecula were parasitized, but a greater proportion of fertile eggs were laid in P. xylostella. Smaller host species were often ignored. Host dissection studies indicated that caged C. torvina were inefficient at host finding and oviposition. Superparasitism was common, but declined as the females gained oviposition experience. Experienced C. torvina produced an average of 8.25 progenies per day for a period of 12 days when provided with 13 P. xylostella hosts each day. Conura torvina produced up to 14 progenies a day when provided 3 26 hosts. Dissection of C. torvina ovaries indicated three ovarioles per ovary with a mean of 9.2 and maximum of 15 mature eggs per female. Host dissection indicated that a mean of 18 and maximum of 30 eggs could be laid per day. New eggs were produced as oviposition occurred. Significantly larger eggs were laid in P. xylostella than in C. rubecula, and significantly more eggs were laid in C. rubecula than in P. xylostella. From these data and data from earlier studies I concluded that C. torvina has a poor reproductive ability and its impact as a hyperparasite is limited to the summer months. This makes C. torvina an unlikely cause of C. rubecula's disappearance. / Ph. D.