Regulation of ciliary pattern in dileptus (Ciliata). II. Formation of a cortical domain of sensory cilia from a domain of locomotor cilia.

The surface of the ciliate Dileptus contains locomotor and sensory domains. Each domain contains cilia of its own kind, arranged in a characteristic pattern. Transformation of a portion of the locomotor area into the sensory domain has been studied. Locomotor ciliary units in the transforming area undergo resorption of ciliary shafts, which are subsequently replaced by shafts of a sensory type. Anterior to each transforming ciliary unit a new one is formed, and both acquire sensory rootlets. As a result, a double-kinetosomal sensory unit emerges. A regulatory change in structure occurs over a definite area that is determined to become the sensory cortical domain.