Host gut microorganisms' cues mediate orientation behaviour in the larva of the parasitoid Mallophora ruficauda.

GROBA, H.F.; CASTELO, M.K.

BULLETIN OF ENTOMOLOGICAL RESEARCH

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2016 vol. 106 p. 81 - 90

0007-4853

P { margin-bottom: 0.21cm; }The robber fly Mallophora ruficauda is one of the most important apicultural pests in the Pampas region of Argentina. This species is a parasitoid of scarab beetle larvae. Females lay eggs away from the host, and the larvae perform active search behaviour toward Cyclocephala signaticollis third instar larvae, parasitoid´s preferred host. This behaviour is mediated by host-related chemical cues produced in hosts´ fermentation chamber. Also, C. signaticollis larvae are attracted to fermentation chamber extracts. As scarab larvae have microbe-rich fermentation chamber, it has been suggested that microorganisms could be involved in the production of these semiochemicals. The aims of this work were first to ascertain the presence of microorganisms in the fermentation chamber of C. signaticollis larvae and second to determine the role of microorganisms in the orientation response of parasitoid and host larvae. We found that microorganisms-free C. signaticollis larvae showed deterioration in their development and did not produce the attractive semiochemicals. Therefore, we isolated fermentation chamber microorganisms of host larvae by means of different cultures media, and then, assayed differentmicroorganisms´ stimuli by binary choice tests. We were able to isolate microorganisms and determine that M. ruficauda larvae are attracted to semiochemicals from protein degradation in the fermentation chamber. However, C. signaticollis larvae were not attracted to any semiochemicals associated with microorganisms´ activity in the fermentation chamber. Although we were unable to elucidate the exact role of gut microorganisms in host behaviour, we discuss their relevance in parasitoid host-seeking behaviour and host conspecific interaction in M. ruficauda-C. signaticollis system.P { margin-bottom: 0.21cm;The robber fly Mallophora ruficauda isone of the most important apicultural pests in the Pampas region ofArgentina. This species is a parasitoid of scarab beetle larvae.Females lay eggs away from the host, and the larvae perform activesearch behaviour toward Cyclocephala signaticollis third instarlarvae, parasitoid?s preferred host. This behaviour is mediated byhost-related chemical cues produced in hosts? fermentationchamber. Also, C. signaticollis larvae are attracted to fermentationchamber extracts. As scarab larvae have microbe-rich fermentationchamber, it has been suggested that microorganisms could be involvedin the production of these semiochemicals. The aims of this workwere first to ascertain the presence of microorganisms in thefermentation chamber of C. signaticollis larvae and second todetermine the role of microorganisms in the orientation response ofparasitoid and host larvae. We found that microorganisms-free C.signaticollis larvae showed deterioration in their development anddid not produce the attractive semiochemicals. Therefore, weisolated fermentation chamber microorganisms of host larvae by meansof different cultures media, and then, assayed differentmicroorganisms? stimuli by binary choice tests. We were able toisolate microorganisms and determine that M. ruficauda larvae areattracted to semiochemicals from protein degradation in thefermentation chamber. However, C. signaticollis larvae were notattracted to any semiochemicals associated with microorganisms?activity in the fermentation chamber. Although we were unable toelucidate the exact role of gut microorganisms in host behaviour, wediscuss their relevance in parasitoid host-seeking behaviour and hostconspecific interaction in M. ruficauda?C. signaticollis system.