Multiple blood meals as a reproductive strategy in Anopheles (Diptera: Culicidae)

Abstract

Multiple blood meals within one gonotrophic cycle were taken readily at 6-24-hr intervals by nulliparous female Anopheles albimanus Wiedemann. Up to five blood meals were ingested and with each blood meal, more primary follicles matured as well as some secondary ones. This produced an irregular oviposition pattern that questioned the concept of gonotrophic concordance. The first blood meal initiated limited vitellogenesis and the maturation of few follicles. Instead, protein was diverted to the synthesis of maternal, extraovarian lipid and protein deposits; fecundity increased with successive blood meals. This pattern of protein and energy utilization may be explained in terms of the low caloric lipid and protein content of nulliparous females before the first blood meal. In An. albimanus, a critical female body size, approximately 0.25 cal of lipid per female, was necessary for the initiation of oogenesis; below this threshold at least two blood meals were required for follicle maturation. Less than 10% of the caloric input from a blood meal was utilized in the synthesis of ovarian protein and lipids, whereas a similar percentage was transferred to maternal deposits of protein and lipid. In nonoogenic females, a replete blood meal increased total body protein and lipid by 17 and 113%, respectively. Altogether, the efficiency of blood protein utilization was rather low, as indicated by losses of excretory nitrogen that regularly exceeded 75% of the input. Anopheles gambiae Giles and An. stephensi Liston also fed multiply, but fecundity was less affected. Instead, maternal deposits were synthesized from the blood meal in substantial amounts. In general, gonotrophic discordance also was found routinely in these anopheline species. The ratio of yolk protein to lipids varied inter- and intra-specifically, as well as among consecutive blood meals, indicating a considerable plasticity in the caloric distribution of these two yolk components.