Unexposed Flies Research Articles

Proximity to parasites reduces host fitness independent of infection in a Drosophila-Macrocheles system.

Parasites are known to have direct negative effects on host fitness; however, the indirect effects of parasitism on host fitness sans infection are less well understood. Hosts undergo behavioural and physiological changes when in proximity to parasites. Yet, there is little experimental evidence showing that these changes lead to long-term decreases in host fitness. We aimed to determine if parasite exposure affects host fitness independent of contact, because current approaches to parasite ecology may underestimate the effect of parasites on host populations. We assayed the longevity and reproductive output of Drosophila nigrospiracula exposed or not exposed to ectoparasitic Macrocheles subbadius. In order to preclude contact and infection, mites and flies were permanently separated with a mesh screen. Exposed flies had shorter lives and lower fecundity relative to unexposed flies. Recent work in parasite ecology has argued that parasite-host systems show similar processes as predator-prey systems. Our findings mirror the non-consumptive effects observed in predator-prey systems, in which prey species suffer reduced fitness even if they never come into direct contact with predators. Our results support the perspective that there are analogous effects in parasite-host systems, and suggest new directions for research in both parasite ecology and the ecology of fear.

Mitey Costly: Energetic Costs of Parasite Avoidance and Infection.

Parasites reduce host fitness via perturbations to host energy allocation, growth, survival, and reproduction. Here, we investigate the independent effects of parasite exposure and infection on host metabolic rate. Our study focuses on Drosophila hydei and a naturally occurring ectoparasitic mite, Macrocheles muscaedomesticae. We use flow-through respirometry to measure the metabolic rate of flies during the period of exposure (preinfection) and during mite attachment. Flies were exposed to mites either indirectly (through a mesh screen) or directly, allowing for physical contact between the fly and the mite. We predicted that fly metabolic rate would increase with the level of parasite exposure: unexposed flies < flies with indirect exposure to mites < flies with direct contact with mites < flies actively infected with mites. As expected, flies indirectly exposed to but not in direct contact with mites produced 70% more CO2 than unexposed flies. Flies in direct contact with mites produced 35% more CO2 than flies with indirect contact, and this was more than double the amount of CO2 produced by unexposed flies. However, infected flies-those actually carrying mites-did not produce significantly more CO2 than uninfected flies. Our results show that simply being exposed to mites, either indirectly or directly, was sufficient to elicit a response from the host in terms of elevated CO2 production. Our results show that the costs of parasitism can potentially extend beyond the physiological costs of infection per se to include the energetic costs associated with parasite avoidance. Although studies have shown energetic costs associate with predator-avoidance behaviors, no study to our knowledge has measured the metabolic cost of parasite avoidance.

Effect of Myricetin on the Oxidative Stress Markers in the Brain of Transgenic Flies Expressing Human Alpha-Synuclein

Background: Parkinson’s disease (PD) is a neurodegenerative disorder having no permanent cure, but there has been a great deal of interest in finding the role of complementary and alternative medicines for the treatment of neurodegenerative disorders. Oxidative stress has also been implicated in the progression of PD. Objective: Since ancient time, natural plant products have been studied for their protective action. In this study, the effect of myricetin was studied on transgenic flies expressing human alpha-synuclein in the neurons. Materials and Methods: The PD flies were allowed to feed on a diet supplemented with 5, 10, and 20 μM of myricetin for 24 days. The flies with PD were then subjected to the study of oxidative stress markers. Results: The results of this study reveal that the exposure of flies with PD to myricetin showed a significant dose-dependent decrease in oxidative stress compared to unexposed flies with PD (P < 0.005). Conclusion: Myricetin is potent in reducing oxidative stress in the brain of flies with PD induced by the expression of human alpha-synuclein and the formation of Lewy bodies.

Social communication of predator-induced changes in Drosophila behavior and germ line physiology.

Behavioral adaptation to environmental threats and subsequent social transmission of adaptive behavior has evolutionary implications. In Drosophila, exposure to parasitoid wasps leads to a sharp decline in oviposition. We show that exposure to predator elicits both an acute and learned oviposition depression, mediated through the visual system. However, long-term persistence of oviposition depression after predator removal requires neuronal signaling functions, a functional mushroom body, and neurally driven apoptosis of oocytes through effector caspases. Strikingly, wasp-exposed flies (teachers) can transmit egg-retention behavior and trigger ovarian apoptosis in naive, unexposed flies (students). Acquisition and behavioral execution of this socially learned behavior by naive flies requires all of the factors needed for primary learning. The ability to teach does not require ovarian apoptosis. This work provides new insight into genetic and physiological mechanisms that underlie an ecologically relevant form of learning and mechanisms for its social transmission.

Cryobiology of the face fly and house fly (Diptera: Muscidae).

Face flies, Musca autumnalis De Geer, have a circumpolar distribution and overwinter as adults in reproductive diapause. House flies, Musca domestica L., have a cosmopolitan distribution and overwinter in northern latitudes in animal confinement quarters. We compared supercooling points with low temperature tolerances, as measured by bioassays, in all developmental stages of both species. There was no correlation between supercooling points and the ability to survive subzero temperatures. Rapid cold hardening was induced in adults of both species by a 2-h acclimation period at 0 degrees C. Hemolymph melting points were measured osmometrically in diapausing and reproductive face flies. Freezing point depressions differed between diapausing and reproductive flies and between reproductive flies given a 2-h pre-exposure to 0 degrees C and unexposed flies. Our data suggest that a -8 to 8 degrees C range with a mean close to 0 degrees C is necessary for successful face fly overwintering. House fly overwintering sites must offer microhabitats that remain above -5 degrees C with sufficient time above 10 degrees C to allow larval, pupal, and ovarian development.