Abstract
BackgroundVariation in longevity has long been of interest in vector biology because of its implication in disease transmission through vectorial capacity. Recent studies suggest that Anopheles coluzzii adults persist during the ~7 month dry season via aestivation. Recently there has been a growing body of evidence linking dietary restriction and low ratio of dietary protein to carbohydrate with extended longevity of animals. Here, we evaluated the effects of dietary restriction and the protein : carbohydrate ratio on longevity of An. coluzzii.ResultsIn our experiment, we combined dietary regimes with temperature and relative humidity to assess their effects on An. coluzzii longevity, in an attempt to simulate aestivation under laboratory conditions. Our results showed significant effects of both the physical and the dietary variables on longevity, but that diet regimen had a considerably greater effect than those of the physical conditions. Higher temperature and lower humidity reduced longevity. At 22 °C dietary protein (blood) shortened longevity when sugar was not restricted (RH = 85%), but extended longevity when sugar was restricted (RH = 50%).ConclusionsDietary restriction extended longevity in accord with predictions, but protein : carbohydrate ratio had a negligible effect. We identified conditions that significantly extend longevity in malaria vectors, however, the extent of increase in longevity was insufficient to simulate aestivation.
Highlights
Variation in longevity has long been of interest in vector biology because of its implication in disease transmission through vectorial capacity
Two separate experiments were carried out using the An. coluzzii, Thierola strain, which was established from six wild-caught females that were collected in Thierola, Mali (13°39'31"N, 7°12'54"W) in November 2012
Longevity and climatic conditions Longevity increased at lower temperature unlike its highly significant interaction with relative humidity (RH) (P < 0.001, Table 3), the main effect of temperature was not statistically significant (P = 0.072, Table 3)
Summary
Variation in longevity has long been of interest in vector biology because of its implication in disease transmission through vectorial capacity. Recent studies suggest that Anopheles coluzzii adults persist during the ~7 month dry season via aestivation. Throughout the Sahel it is the only species that persists during the seven month long dry season (when no surface water is available) beginning its population growth soon after the first. Additional key changes during the dry season include depressed reproduction [9], depressed flight activity [15], increased desiccation tolerance linked to changes in cuticular hydrocarbons [21] and metabolic and protein changes [13, 22], but not lower metabolic rate [15]. Changes in protein/carbohydrate catabolism may be key to the induction and maintenance of aestivation as suggested, by formation of long-lived dauer-state larva in Caenorhabditis elegans (Maupas, 1900) (Rhabditida: Rhabditidae) carrying mutations at the insulin and IGF-I receptors [25, 26]. Lifespan extension seems to be mediated through a number of nutrition-linked metabolic pathways [32], often at the cost of reproduction [33]
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