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Undulatory locomotion of the plant parasitic nematode Meloidogyne javanica
Published online by Cambridge University Press: 06 April 2009
Extract
A hypothesis is developed to explain how the nematode propels itself around in the egg before hatching. The normal reactions at the ends of the egg to the pressure exerted by the nematode are each equivalent to a force propelling the nematode around inside the egg and to a displacement force. A diagram of forces that satisfies the requirements for undulatory locomotion has an asymmetrical egg with ends of variable curvature. In such an egg the only effective forces acting on the nematode are the propulsive forces along the longitudinal axis of the nematode and frictional forces between the nematode and egg shell. A steady glide occurs when these two forces are equal. As the nematode moves around the ends of the egg, the muscles in contact with the shell come under tension and owing to the change in curvature of the shell they contract and release the potential energy necessary for propulsion.
Measurements on the shape of eggs, the configurations of actively moving nematodes in the egg, ciné film of eggs and a model of a nematode in an egg do not disprove the hypothesis.
Prior to hatching the surface area of the egg increases and increased force by the head of the nematode at one end of the egg produces a protuberance which eventually bursts under the influence of the mouth stylet which punctures the shell and the pressure from the nematode's head. Propulsive forces within the egg enable the larva to hatch.
Nematodes at a root surface form waves of large amplitude with the result that the head and stylet often meet the root at right angles. The nematode then attaches itself to the root and active use of the mouth stylet makes the initial puncture in the plant's epidermis. Penetration to a depth of 100 μm occurs under the influence of propulsive forces developed by that part of the body outside the root. Thereafter, the section of the body within the root develops the necessary forces and the posterior part outside the root remains almost stationary. The nematode penetrates the root intermittently to a depth of 40–60 μm every 20–40 min corresponding to the penetration of a series of cell walls.
The relationships between egg shape, movement in the egg, mode of hatching and site of hatching present a further interesting problem because it is possible that nematodes that hatch into an environment outside the host require some pre-hatch movement to bring the muscular system to a high level of efficiency. Nematodes that hatch within the host may not need such an adaptation.
Thanks are due to Mr I. R. Dick for his help and useful discussion, to Mr K. W. J. Crocker for technical help and to Miss Colleen Hill who made the drawings.
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- Copyright © Cambridge University Press 1968
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