Proliferation of microtubules from discrete electron-dense bodies in the ciliary dendritic portion of mechanosensory setae of copepod antennae

Abstract

Sensory setae on the appendages of most arthropods contain microtubules in their innervating dendrites. Both mechano- and chemoreceptors are of ciliary origin. Mechanoreceptive dendrites typically contain more microtubules than do chemoreceptive dendrites, perhaps reflecting a role for microtubules in stiffening the setae. The presence of microtubules may also increase the sensitivity of mechanotransduction.The overall arrangement of calanoid copepod mechanoreceptors has been described elsewhere. In calanoid copepods the arrangement of microtubules in the distal ciliary segment of the dendrites is dramatic: as many as 3000 microtubules per dendrite are found in parallel rows (fig. 1,3a). These bundles of microtubules extend some distance into the setae themselves. The basal bodies within these dendrites are especially electron-dense and give rise to a circlet of 9 + 0 microtubules (fig. 2,3f)- Just distal to the circlet electron-dense material begins to form adjacent to the microtubules (fig. 3e), eventually forming elongate electron-dense bodies radiating outward (fig. 3d).