Title

DO UNDERGROUND CHAMBERS PROTECT MANDUCA SEXTA CATERPILLARS FROM PARASITIC NEMATODES?

Presenter Information

Siobhan Kirkpatrick

Presentation Type

Poster

Abstract

At the end of their fifth instar, larvae of Manduca sexta (the tobacco hornworm) descend from their host plants and burrow into nearby soil where they form pupation chambers. Larvae expend significant proportions of their body mass in water and energy to form these chambers, suggesting that chambers play some important role. That role, however, remains a mystery. My research investigates the hypothesis that underground chambers protect caterpillars from entomopathogenic (insect infecting) nematode attacks either by physically protecting caterpillars from infection or by camouflaging CO2 signals emitted by the caterpillars during respiration. I examined how readily nematodes infect larvae, pre-pupae, and pupae in Petri dishes and different soil conditions. In Petri dishes, larvae were more susceptible to nematode infection than pre-pupae or pupae. However, in varying soil-water concentrations, neither pupae nor larvae were infected by nematodes regardless of chamber presence or absence. To determine if chambers camouflage CO2 signals emitted by M. sexta, making them less conspicuous to nematodes, I constructed dirt columns in sections of Plexiglass pipe, varied chamber presence, released CO2 either continuously or discontinuously, and measured nematode concentrations in 1cm increments throughout the dirt. The results of this study are still under consideration. By exploring if nematodes can infect late instar M. sexta and if chambers mask CO2 signals, at least one possibility of chamber function can be accepted or rejected. This research may also have greater societal significance. For example, to effectively use nematodes as biological control agents, their interactions with potential hosts must be well understood.

This document is currently not available here.

Share

COinS
 
Apr 15th, 11:00 AM Apr 15th, 12:00 PM

DO UNDERGROUND CHAMBERS PROTECT MANDUCA SEXTA CATERPILLARS FROM PARASITIC NEMATODES?

UC South Ballroom

At the end of their fifth instar, larvae of Manduca sexta (the tobacco hornworm) descend from their host plants and burrow into nearby soil where they form pupation chambers. Larvae expend significant proportions of their body mass in water and energy to form these chambers, suggesting that chambers play some important role. That role, however, remains a mystery. My research investigates the hypothesis that underground chambers protect caterpillars from entomopathogenic (insect infecting) nematode attacks either by physically protecting caterpillars from infection or by camouflaging CO2 signals emitted by the caterpillars during respiration. I examined how readily nematodes infect larvae, pre-pupae, and pupae in Petri dishes and different soil conditions. In Petri dishes, larvae were more susceptible to nematode infection than pre-pupae or pupae. However, in varying soil-water concentrations, neither pupae nor larvae were infected by nematodes regardless of chamber presence or absence. To determine if chambers camouflage CO2 signals emitted by M. sexta, making them less conspicuous to nematodes, I constructed dirt columns in sections of Plexiglass pipe, varied chamber presence, released CO2 either continuously or discontinuously, and measured nematode concentrations in 1cm increments throughout the dirt. The results of this study are still under consideration. By exploring if nematodes can infect late instar M. sexta and if chambers mask CO2 signals, at least one possibility of chamber function can be accepted or rejected. This research may also have greater societal significance. For example, to effectively use nematodes as biological control agents, their interactions with potential hosts must be well understood.