Quarterly Journal of Microscopical Science, Vol s3-92, 129-140, Copyright © 1951 by Company of Biologists

The Structure, Development, and Operation of the Hinge Ligament of Ostrea edulis

¹ Department of Zoology, University College, Hull

1. The ligamental structure of Ostrea edulis is briefly described. The ligament is situated between the valves of the shell immediately below the urtibo and may be divided into two main layers, the outer and the inner, the principal features of which appear to correspond with those of other bivalves. The outer layer is divided into anterior and posterior halves by the inner layer, which occupies a central position.

2. The axis (hinge or pivotal axis) about which the valves open is situated in the adult oyster along a line drawn through the outer layer and the upper part of the inner layer. When the valves are closed the ligament above this axis is subjected to a tensile strain andthat portion below to compression, the force s so produced causing the opening of the valves. An attempt has been made t o measure this force in relation to the surface area of the valves and it is found to be approximately 4.5 gm.mm./mm.² This figure is comparable to those obtained when certain other species of bivalves are used.

3. Th eligament is shown to develop from the simple outer layer of the early larval stages, first by the addition of aninner layer and then by growth of this structure chiefly in a ventral direction. The initial dorsal region of the ligamentsoon degenerates and at the same time the pivotal axis moves ventrally between the valves, thus increasing in length. This method of growth is compared with that of an elongate external ligament and the mechanical implications are suggested.