Studies on Dictyocaulus filaria. IV. The morphogenesis of the parasitic stages in lambs

Abstract

In males the parasitic 3rd stage, 3rd moult, 4th stage, 4th moult and 5th stage are reached on Days 1 to 2, 3, 4, 5 to 6 and 8 respectively. The 4th stage is swollen in the anal region and accessory genitalia differentiate rapidly during the 4th moult. In females development from 4th stage larvae through the 4th moult to the early 5th stage is delayed ; these stages are present from Days 4 to 6, 7 and 8 respectively. There is little differentiation in the 3rd stage. In the 4th stage the tail has become tapered and by the 4th moult the vulva lips have formed ; they become patent after moulting. The genital ducts start showing evidence of patency only 7 days after the 4th moult completing this process 10 days later. The uterus contained embryonated eggs on the 28th day.