Endogenous regulation of mosquito host-seeking behavior by a neuropeptide

Abstract

Most species of mosquitoes must engage in host-seeking behavior to find a vertebrate host and ingest a meal of blood in order to initiate and complete each oögenic cycle. Female Aedes aegypti fed to repletion almost immediately fail to respond to odor cues that would otherwise lead them to a host for another blood meal. This response is delayed for approx. 24h in females that ingest small blood meals. In both instances, during this period of inhibition, the hemolymph titer of Ae. aegypti Head Peptide I (Aea-HP-I; pGlu-Arg-Pro-Hyp-Ser-Leu-Lys-Thr-Arg-Phe-NH 2) rises to a peak, as measured with an Aea-HP-I radioimmunoassay (RIA). This homologous RIA is based on an antiserum that specifically binds Aea-HP-I (5–100 fmol range, 1:100,000 final dilution) as compared to other related peptides, Aea-HP-I and at least one other immunoreactive peptide were identified in pooled hemolymph from sugar-fed females with HPLC fractionation and the RIA. To determine whether Aea-HP-I affects host-seeking behavior, synthetic Aea-HP-I and related peptides were injected into non-oögenic females, which actively seek a host. Host-seeking behavior was inhibited by Aea-HP-I within a dosage range of 16.5–825 pmol/female, whereas related peptides differing by a few amino acids had no effect. The relatively high doses of Aea-HP-I, which elicited behavioral inhibition, were rapidly degraded in vivo as determined with the RIA of hemolymph from experimental females. Other associated behaviors were not altered by the Aea-HP-I injection, even at high doses. These results together suggest that Aea-HP-I regulates the observed behavioral inhibition in this mosquito species.