Description of the lateral line organ of Dikerogammarus villosus (Sowinsky, 1894), with discussion on its function (Peracarida, Amphipoda). Amphipod Pilot Species Project (AMPIS) - Report 4.

Abstract

The lateral line organ of Dikerogammarus villosus (Sowinsky, 1894), consisting of two rows of sensory units along each side of the body, is described and its function discussed. All somites possess one lateral and one dorsal sensory unit on each side, except for the second urosomite, where only a lateral unit is present. Each receptor unit consists of a nearly straight or curved cuticular depression with a row of microtrichs. The flattened microtrichs are not varying with sex or size and are of equal length and width. The depressions from which the microtrichs arise are of constant depth. The distances between the individual microtrichs in all units are equal. However, the number of microtrichs per unit is body-size dependent with the highest number in the largest specimens. The orientation of the individual microtrichs in a unit varies from multi-angular (either fan-shaped, L-shaped, or question mark-shaped) in most anterior units, to parallel or perpendicular to the middorsal line in some posterior units. The microtrichs themselves are elliptical and hollow, with the outer mantle enclosing a central filament in its elliptical inner space, presumably of sensory function. A combined chemo-, mechano-, and electro-sensory function with respect to their arrangement and their morphology, is discussed.