Many insects are able to adjust their egg production according to physiological conditions such as nutrient supply and mating success. One way in which this is achieved is by resorption of some, or all, of the ovarian follicles at some stage during oogenesis. We have shown that the mosquito Anopheles stephensi responds in this manner when ookinetes of the malaria parasite Plasmodium yoelii nigeriensis first begin to invade the midgut. Little is known about the initiation and regulation of follicle resorption in any insect.

We have used Anopheles gambiae, a major vector of malaria in Africa, to test the
hypothesis that the operation of a surveillance or immune system against microorganisms
and parasites can be costly to the reproductive success of the host. Blood-fed
mosquitoes were challenged with an immune elicitor, lipopolysaccharide (LPS), and
their resultant antimicrobial activity, accumulation of yolk protein in the ovary and
egg production was monitored. Humoral activity against the Gram-positive bacterium

Melanization is the main immune response killing malaria parasite in the gut of the malaria refractory mosquitoes. This study investigates this response against Sephadex beads model in the malaria susceptible Anopheles gambiae at 20 h post-beads inoculation. Follicular apoptosis and resorption have been investigated as two suggested mechanisms underlying reproductive costs as a result of this immune response. Thus, one of two different beads was inoculated into mosquito thoracic haemocoel, either a negatively charged CM C-25 or a neutral CM G-25 one.

The mosquito Anopheles gambiae, the major vector of malaria in Africa, was used to test the hypothesis that the utilization of immune system against malaria parasites could be possible. Two immune elicitors, the bacteria, Micrococcus luteus and the black-seed (BS) oil, Nigella sativa, were used to stimulate the immune system of this vector against the rodent malaria parasite, Plasmodium yoelii nigeriensis. Mosquitoes were inoculated with bacteria or allowed to orally feed on glucose-oil mixture both before and after malaria infection.

In this study, induction of the humoral anti-bacterial activity of the African human malaria vector, Anopheles gambiae, and the mechanisms of the concomitant fecundity reduction were investigated. The blood meal induced a humoral anti-Micrococcus luteus activity, which was detectable at 12h, peaked around 24h and become hardly detectable at 48h post-feeding. This humoral activity was also detected in sugar-fed mosquitoes at 18h post-intrathoracic injection with the immune elicitor, lipopolysaccharide (LPS, 10ng/mosquito).

costs have been associated with both humoral and cellular innate immune responses and also with malaria infection. The resorption of developing oocytes associated with malaria infection is preceded by the programmed cell death, or apoptosis, of follicular cells. Here we demonstrate that apoptosis in ovarian follicular epithelial cells also occurs when mosquitoes are subjected to artificial immune-elicitors that induce a melanization response or humoral antimicrobial activity. Caspases are key cysteine proteases involved in apoptosis.

Great efforts are currently being done to utilize the immune system of mosquito vector in the battle against malaria. However, this strategy still facing some limiting factors mainly the reproductive cost, the price of immune induction. This study has been introduced to show that inducing non-costly immune responses in the African malaria vector, Anopheles gambiae, is possible via the oral administration of black seed oil (BSO), a natural botanical extract from Nigella sativa, to mosquitoes.