GROWTH AND MOLTING IN NEMATODES - MOLTING AND DEVELOPMENT OF THE HATCHED LARVA OF ROTYLENCHULUS-RENIFORMIS

The morphology of the posthatch molting and developmental sequence of an amphimictic population of R. reniformis was examined in living and fixed material. Under suitable conditions of temperature and in a moist environment the 2nd stage larva (L2) undergoes a series of 3 molts and developmental changes which result in the formation of males and immature females. After hatching and prior to the start of the 1st of these molts (the 2nd molt), there is a premolt period, usually of 3-5 days duration. The morphology of the entire molting and developmental sequences, from L2 to just after the final molt, was followed in single living specimens of a parasitic nematode using differential interference contrast optics, and sections cut through different stages were observed under the transmission electron microscope. These molting sequences (at 24.degree. C) take place at similar times in developing males and females. The 2nd molt takes place on the 2nd day after commencement of molting, the 3rd on the 3rd or 4th days and the 4th and final molt on the 6th or 7th days, followed by further development over several days to give rise to the adult male and the immature female. The ultrastructure associated with some of the more obvious of these developmental changes is described and includes the morphology of the head region and cuticles of L2, L4, adult males and immature females, the esophageal glands of the immature female and the copulatory spicules and spermatozoa of the male.