, Volume 91, Issue 3, pp 235-248

A new function of rhabdites: Mucus production for ciliary gliding

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Rhabdites are rod-shaped secretory products characteristic of the Turbellaria but also found in nemerteans, gastrotrichs and annelids. Their functions are poorly understood. The structure, synthesis and secretion of rhabdites were studied in one archiannelid (Protodrilus sp.), and three turbellarians (Alloioplana californica, Polycladida;Monocelis cincta, Alloeocoela;Polychoerus carmelensis, Acoela). InAlloioplana, Monocelis andPolychoerus the rhabdites are the only, or most common, secretory product released on the ventral locomotor sole and therefore they are thought to form the viscous mucus used in locomotion by ciliary gliding. InProtodrilus, rhabdites are released along the ventrolateral margin of the worm and are secreted only when the worm tries to move by ciliary gliding against strong water currents. It is proposed that the principal function of rhabdites in the worms studied, is adhesion.

I acknowledge the support of a NIH grant to Professor Richard M. Eakin, the collection ofPolychoerus by Mr. Charles Spowart, the use of the facilities of the Electron Microscope Laboratory at Berkeley, and the critical reading of the manuscript by Dr. Eakin