Metabolic and Behavioural Response of Drosophila nigrospiracula to Ectoparasite Infection

• Author / Creator

  Brophy, Taylor Raymond

• Parasite aggregation is a population-based metric in which many hosts harbour few parasites but some hosts are infected by a large number of parasites. The causes of aggregation are primarily attributed to heterogeneity in host exposure and susceptibility. However, parasites can exert numerous effects upon their hosts, including physiological and metabolic changes that can in turn influence various aspects of host life history. I hypothesized that the parasites themselves can potentially generate aggregation within host populations. Host behavioural defences can vary depending on intrinsic and extrinsic factors, such as current infection status, yet few researchers have examined the impact of current infection on the efficacy of host defences against future parasite attack. To test my hypothesis, I used the Drosophila nigrospiracula-Macrocheles subbadius host-ectoparasite study system. I predicted that increasing mite load would increase susceptibility to future mite attachment. I also predicted that the increase in susceptibility would be mediated by a parasite-induced reduction in host defensive behaviours. I used laboratory experiments and an activity monitor to: (1) determine the relationship between parasitic infection intensity and host susceptibility and (2) examine the effect of infection intensity on a host’s overall level of activity when exposed to another parasite. Results indicate that host susceptibility to future infection increased with higher current infection intensity. Activity of infected hosts change, though not in the expected direction, based on infection intensity and host sex. Parasites may also be able to affect other host traits such as host respiration that in turn may influence mite selection for certain hosts. Using flow-through respirometry, I investigated how attachment by parasites and infection intensity of the mite affects the respiratory rate of the host. In a before-and-after mite attachment experiment, the mean respiratory rate (CO2 production) of flies increased after infection by mites. I also found that mean fly respiratory rate increased with infection intensity, with the strongest effect occurring with 3 mites. Changes in host metabolism did not appear to be mediated wholly through increased activity among infected flies. These results show that infection by ectoparasites carry metabolic cost for hosts in an intensity-dependent manner. All together, I identify a mechanism by which a parasite alters host susceptibility and parasite load, indicating the importance of examining parasite-driven effects on aggregation within a host-parasite system.

• Subjects / Keywords

  • Metabolism
  • Susceptibility
  • Infection
  • Parasite

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-qgb0-7646

• License

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