Ultrastructural Changes Associated with Development of Pin Namatode, Graculacus sp., with Special Reference to Its Survival : Ecological significance of dormancy in plant parasitic nematodes. VIII

The 4th stage larvae (L4s) of Gracilacus sp.2 prior to lethsargus withstand unfavorable conditions for a longer time than lethargic L4s and adults; for more than 42 months in soil kept in polythene bags and at least 80 days in water-saturated soil. For all thicknesses of cuticle, the ratio of the external cortical and basel layer of the quiescent L4s was ca. 10% and 55%, respectively, being the largest in all stages examined. With the development of L4s to adulthood, the permeability of cuticle increased. The intestinal cells of L4s were filled with lipid droplets, which decreased in amount and some of which changed into the age pigment granules in adults. In the course of the formation of adult cuticle, electron dence balls appeared in the lateral hypodermis of the lethargic L4s. Changes in survivability with development is discussed from an ultrastructural viewpoint.