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Changes Associated with Parasitism in Nematodes. III. Ultrastructure of the Egg Shell, Larval Cuticle, and Contents of the Subventral Esophageal Glands in Meloidogyne javanica, with Some Observations on Hatching
Alan F. Bird
The Journal of Parasitology
Vol. 54, No. 3 (Jun., 1968), pp. 475-489
Stable URL: http://www.jstor.org/stable/3277069
Page Count: 15
You can always find the topics here!Topics: Eggs, Nematode larvae, Hatching, Eggshells, Roundworms, Animal glands, Larval development, Lipids, Larvae, Electron micrographs
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Egg development proceeds normally under the influence of a number of environmental stimuli. Hatching is associated with an increase in larval activity and plasticity of the egg shell resulting from the breakdown of a lipid layer. During this period protein granules are formed in the subventral esophageal glands. The fine structure of the egg shell during different stages of larval development is described together with structural changes which take place both in the cuticle and in the subventral esophageal glands of the larva during its transition from the preparasitic to the parasitic mode of life. The egg shell consists of two basic layers; an outer chitinous layer, and an inner lipid layer. The former is about 0.5 µ thick and has a dense outer layer which is about 30 mµ thick. The lipid layer varies in thickness and appears to break down just before hatching. The cuticle of the preparasitic larva is just over 0.3 µ thick. It is characterized by a pronounced striped layer which disappears within a week of the nematode becoming a parasite. The granules in the subventral esophageal glands of preparasitic larvae are about 0.6 to 0.8 µ in diameter, irregular in shape, and have a distinct outer membrane, in contrast to granules in the subventral esophageal glands of parasitic larvae which lack a distinct outer membrane, are smaller, and have contents which stain differently. These observations support those made earlier with the light microscope and the U.V. microspectrograph.
The Journal of Parasitology © 1968 The American Society of Parasitologists