THE CILIARY JUNCTIONS OF SCALLOP GILLS: THE EFFECTS OF CYTOCHALASINS AND CONCANAVALIN A

¹ Department of Biological Sciences, Florida State University, Tallahassee, FL 32306

The ciliated junctions between the gill filaments of scallop gills were studied. Junctional cilia are borne on both sides of spurs of tissue—cilifers—extending from the filaments. In an intact junction, each cilium is paired with another cilium from a cilifer on a neighboring filament. An electron dense band underlies the plasma membrane of each junctional cilium along the line of apposition with its mate.

Cytochalasins A, B, and E caused gill test square preparations to break up into their component filaments. All three cytochalasins disrupted the electron dense band, and cytochalasins A and E also disrupted the ciliary microtubules. These effects were reversible.

The paired adhesion of the junctional cilia was also reversibly inhibited by treatment with Concanavalin A (Con A; 100 µg/ml). Con A bound to the surface of the junctional cilia was labeled with hemocyanin. After treatment with Con A alone, the label was lightly and evenly distributed over the shafts of the cilia, but was more densely concentrated at their tips. In cytochalasin-Con A preparations, the surface labeling of the junctional cilia increased with the duration of cytochalasin exposure.

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