Developmental biology of a predatory soil nematode, Mylonchulus minor

Mylonchulus minor reproduced parthenogenetically with no males in the population. The eggs laid were ovoid, smooth-shelled and always in single-celled condition. The two blastomeres formed after first cleavage divided simultaneously and gave rise to four-celled condition. The embryo moved for the first time during “tadpole” stage. Hatching occurred as a result of rupture of the shell which became thin and flexible due to the pressure exerted by the juvenile. The gonad developed from two small genital primordia placed obliquely, on each side of intestine, in the first stage juvenile. The germinal nuclei of primordium remained undivided until third moult after which their number increased. The juvenile stages could be diferentiated more precisely on the basis of primordial development as other morphometric and allometric ratios showed high degree of overlap subsequent to second stage.