A comparative study of induced increases in proximal recombination in Drosophila melanogaster females

Crossing over was studied in Drosophila melanogaster females between f – car – bb1– Dp(y+) on the X chromosome. Mitomycin C and γ-rays increased crossing over in all three regions, increased nondisjunction and affected meiotic as well as gonial cells. Temperature was recombinagenic only in the car – bb1regions and the autosomal inversions Cy and Ubx130increased crossing over in both regions containing euchromatin (f – car and car – bb1). Actino-mycin D-treatment resulted in a slight decrease in crossing over. The data indicate that there may be two general classes of recombinagens, those that affect crossing over in proximal euchromatin and those which in addition, induce breaks in heterochromatin.

Infection and reinfection of Culex pipiens fatigans with Wuchereria bancrofti and the loss of mature larvae in blood-feeding

Although previous workers had found no evidence of resistance to superinfection in vectors of filariasis, it was considered desirable to reinvestigate the subject because of the epidemiological implications, since a mosquito that can incubate to maturity successive broods of filarial larvae will obviously be a more efficient vector than one that cannot. The results obtained indicate that a Culex pipiens fatigans mosquito that picks up an infection early in its life can, by taking subsequent infecting feeds, remain infective for the rest of its life.The movement of mature larvae in the vector and losses of larvae during feeding are of interest since from this information one can estimate the probable number of larvae deposited on the host at each feed and the period of infectivity of the vector. In the present experiment there were, on average, 6.1 larvae per infective mosquito before a second blood-meal; after the meal the figure was 3.6. Thus, 41% of the original infective larvae were lost; not all would be inoculated into the host, as some would die on the surface of his skin. The release of infective larvae through blood-feeding results from a combination of the passive pressure of the engorged blood in the abdomen and the active movement of the larva itself.