The Ciliary Junctions of Scallop Gills: The Effects of Cytochalasins and Concanavalin A

Abstract

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 ^g/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.

The gill morphology of the date mussel Lithophaga lithophaga (Bivalvia: Mytilidae)

“…The aligned rows of ciliary discs with their evident distribution pattern in Lithophaga appear to function primarily to protect the filaments from hydrodynamic forces and to regulate the flow of water through the interfilamentary spaces. The mechanical adhesion of the ciliary junctions has previously been described in an ultrastructural study of the ciliary tips in scallop gills (Reed-Miller and Greenberg, 1982).…”