Plasmodium infection decreases fecundity and increases survival of mosquitoes

Abstract

Long-lived mosquitoes maximize the chances of Plasmodium transmission. Yet, in spite of decades of research, the effect of Plasmodium parasites on mosquito longevity remains highly controversial. On the one hand, many studies report shorter lifespans in infected mosquitoes. On the other hand, parallel (but separate) studies show that Plasmodium reduces fecundity and imply that this is an adaptive strategy of the parasite aimed at redirecting resources towards longevity. No study till date has, however, investigated fecundity and longevity in the same individuals to see whether this prediction holds. In this study, we follow for both fecundity and longevity in Plasmodium-infected and uninfected mosquitoes using a novel, albeit natural, experimental system. We also explore whether the genetic variations that arise through the evolution of insecticide resistance modulate the effect of Plasmodium on these two life-history traits. We show that (i) a reduction in fecundity in Plasmodium-infected mosquitoes is accompanied by an increase in longevity; (ii) this increase in longevity arises through a trade-off between reproduction and survival; and (iii) in insecticide-resistant mosquitoes, the slope of this trade-off is steeper when the mosquito is infected by Plasmodium (cost of insecticide resistance).

Avian malaria: a new lease of life for an old experimental model to study the evolutionary ecology ofPlasmodium

“…Despite earlier results showing that, under certain experimental conditions, P. relictum infections are associated with an increase in mosquito longevity [12], here we found no clear association between Plasmodium infection and mosquito longevity, although slight differences in the experimental protocols may have blurred the picture. We did, however, find an intriguing positive relationship between bird parasitaemia and mosquito survival (figure 8).…”

“…For this reason, the effects of Plasmodium infection on mosquito life-history traits such as fecundity and lifespan have received a lot of attention [58,59]. The largest effect of P. relictum parasites on Culex mosquitoes is a drastic reduction in their fecundity, which can result in a loss of up to 40% of eggs laid [12]. Our findings are consistent with these previous results qualitatively, if not quantitatively: infected females laid on average 11.5% fewer eggs than their uninfected counterparts.…”

Evidence for carry-over effects of predator exposure on pathogen transmission potential

“…Whether malaria parasites cause fitness costs to the mosquito vectors remains disputed [45,46]. Most studies on the costs of malaria infection have been conducted under optimal laboratory conditions.…”

Plasmodiuminfection brings forward mosquito oviposition

“…Here, we test whether Plasmodium-infected mosquitoes oviposit earlier than their non-infected counterparts. To do so, we use the Culex pipiens-Plasmodium relictum system, which combines a mosquito characterized by its strong flexibility regarding the timing of egg-laying [9,10] and a parasite that drastically reduces its fecundity [3]. Bringing forward the age of oviposition is expected to come at a cost, which only the fittest mosquitoes may be able to bear.…”