The Feeding Pump of Ditylenchus Dipsaci (Nematoda: Tylenchida)

Abstract

The action of the oesophageal feeding pump of Ditylenchus dipsaci during feeding has been analysed, principally by high-power interference-contrast cinemicrography. A cross-section of the central muscular part of the pump shows only 30 % myofibrillar area and there is still less contractile tissue towards the anterior and posterior ends of the pump. The pump shortens and widens as the lining is opened and becomes longer and thinner when the lining closes, and swelling of the radial muscles normal to their line of action jams them together, providing anchorage for them to open the lining. But some parts of the radial musculature are squeezed outward when active so that the anterior muscles shorten by > 4 % , but the middle and posterior muscles by half this or not at all. When the sclerotised pump lining opens from triradiate to triangular cross-section, equatorial and polar radii increase and decrease by about 15 %; similar values were obtained with a manipulated scale model. The lining opening involves transient distortion into compound curves, but the fully-open (triangular) condition is quite stable and on closing is destabilised by a nearly longitudinal pull from the posterior radial muscles. The pump lining rotates within the pump during pumping. A value of 1-2 x 10 6 μm 3 is estimated for daily intake by one nematode. Transient and variant activities associated with pumping are described and discussed. Dorsal gland secretions were displaced by radial muscle action and by that of an anterior radial muscle complex that stiffens the oesophageal wall just anterior to the pump, but cannot open its thickened circular lining. Passive inflow of food from a cell, already known, can occur through the residual open lumen of the closed feeding pump lining. Properties of various tissues, their role as energy stores for closing the lining and their role in a probable myogenic click mechanism for pumping are discussed in some detail. The barely detectable anterior to posterior sequence of opening, and the possibility of non-simultaneous opening of the three pairs of pump plates are considered, and the arrangement and functions of anterior muscle complexes and of the sticky oesophago-intestinal valve are discussed.