Mosquito ( Culex pipiens pallens) egg development induced by infusion of amino acids into the hemocoel

Abstract

A mixture of amino acids was infused into the hemocoel of female Culex pipiens pallens mosquitoes at a very slow rate. We attempted to simulate the natural concentration increase of hemolymph amino acids, in order to determine whether amino acids derived from a blood meal trigger mosquito oögenesis. Infusion of a 7.5% (w/v) amino acid mixture for 14–16 h at a flow rate of 0.083 μl/h (2.0 μl/24h) activated oöcytes to develop to intermediary stages (stages IIb-IIIa). The same infusion continued for more than 20 h resulted in egg maturation in most of the treated females. The number of mature eggs was not significantly different among the 14–24 h infusions but showed a proportional increase between the 24 and 48 h infusions. The hemolymph amino acid concentrations of these infused females did not greatly differ from the levels observed in blood-fed females, suggesting that the oögenic stimulatory effect of the infused amino acids was close to the natural process. This indicated that amino acids resulting from blood meal digestion are not only utilized for yolk protein synthesis but also have the potential to initiate and promote mosquito oögenesis. In addition, oöcyte growth caused by infusion without any distention of organs or body wall clearly indicates that stretching is not an essential trigger for this event.