Developmental biology of Dorylaimus stagnalis Dujardin, 1845 (Nematoda: Dorylaimida)

The observations are made on the embryonic and post-embryonic developments of Do ylaimus stagnalis. The eggs, measuring 71-95 x 33-45 (82 x 39) Fm, are smooth, elongate oval, densely granulated and dark brown in colour. The first cleavage is perpendicular to the long axis of the egg and appears 15-24 h after the egg was laid. The blastula and gastrula stages are formed 40-90 and 75-90 min after the first cleavage. The tadpole stage is formed 215 min later and the juvenile hatched out of the egg 6 h after the formation of their interna1 organs. Maximum hatching is recorded at temperatures 30-35 OC. The first stage juveniles have two germinal and 4-6 somatic nuclei in the genital primordium; the second stage have 4-6 germinal and 8-14 somatic nuclei. The third stage have 8-12 germinal and 20-45 somatic nuclei. The fourth stage female and male have 20-60 and 18-61 germinal nuclei respectively. The first stage juveniles require 17-22 days for moulting; the second 24-28 days; the third 30-35 days. The fourth stage female and male require 46-52 and 40-45 days for their development, respectively. In the fourth and final moult, the long fiiiform tail of fourth stage male juveniles transforms into a short conoid tail. The otal time (from hatching to adult) of males varie