WATER-LOSS AND MORPHOLOGICAL-CHANGES DURING DESICCATION OF THE ANHYDROBIOTIC NEMATODE DITYLENCHUS-DIPSACI

Ditylenchus dipsaci is an anhydrobiotic nematode which can withstand d irect exposure to extreme desiccation. Water loss has been determined gravimetrically and morphological changes quantified by light microsco py. Water loss occurs in two distinct phases, with a permeability slum p 2 min after the onset of desiccation. The permeability slump remains after treatment with sodium azide or carbon dioxide but disappears af ter heat treatment. There is a marked decrease in body length during t he first 2 min of desiccation but diameter decreases throughout the de siccation period, mainly as a result of a decrease in the thickness of the hyaline layer. These observations suggest that one mechanism by w hich the nematode controls water loss during desiccation is by narrowi ng the groove between annulations. They also provide measurements on l iving nematodes which can be compared with more detailed observations using electron microscope techniques.