The effects of certain cations and antibiotics on blood digestion in two species of mosquitoes

Abstract

Immediately after emergence as adults, female Aedes aegypti and Anopheles quadrimaculatus mosquitoes were fed on sugar solutions containing the chlorides of either calcium, magnesium, manganese, or iron in various concentrations, the antibiotics oxytetracycline, neomycin, streptomycin, and penicillin, or the antibiotics in combination with each other or in combination with the cations. After feeding on these solutions for approximately 4 days, the mosquitoes were allowed to take a blood meal, and either 72 or 96 hr later, when normally digestion would have been completed, the stomachs were examined microscopically for evidences of blood residues. It was found that calcium, magnesium, manganese, and iron all inhibited blood digestion to varying degrees in both A. aegypti and A. quadrimaculatus. The antibiotics, however, acted in a more complicated manner and produced a variety of effects. Thus, oxytetracycline, for example, had scarcely any inhibitory effect in Aedes, yet when fed to the mosquitoes in combination with either calcium, magnesium, or manganese it produced a substantial potentiation of the cation effect, whereas in combination with iron it suppressed almost entirely the effect of the latter. In the anophelines oxytetracycline had a marked inhibitory effect yet its potentiating effect was apparent only in combination with manganese, although it still suppressed the effect of iron. In Aedes, penicillin suppressed the inhibitory effects of calcium, manganese as well as oxytetracycline and neomycin, whereas in Anopheles it had instead a limited inhibitory effect, although again in this species it also acted to suppress the inhibition produced by oxytetracycline and neomycin. Whereas in Aedes the inhibition produced by neomycin was suppressed by iron, in the anophelines neomycin and iron together had an additive inhibitory effect. These results indicate that the in vivo effect of a particular antibiotic on a given physiological system is a function of the animal species, and that this effect is further modified by the presence of certain cations or other antibiotics.