Desiccation survival in the plant parasitic nematodes,Heterodera rostochiensisWollenweber andDitylenchus dipsaci(Kuhn) Filipjev

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Abstract
Using interference microscopy, it is shown that the free second-stage larva of the potato-root eelworm,Heterodera rostochiensis, takes up water at the same rate as one still inside the eggshell; the enclosed larva, however, loses water far less rapidly. It is considered that the shell, freely permeable to water when wet, becomes increasingly impermeable as it dries; the resulting reduction in the rate at which the enclosed larva dries, to which the cyst wall will also contribute, is thought to be of decisive importance for survival. Mechanisms of a similar kind probably operate in the fourth-stage larva of the narcissus strain ofD. dipsaci, both in the ‘eelworm wool’ aggregations and in the isolated individual larva. In the aggregations, nematodes on the outside of the mass died first: they also dry sooner. There is evidence that, in the isolated larva, a decrease in the perm eability of the drying cuticle slows the drying of deeper layers of the organism.