Morphometric and ultrastructural studies of shape and pattern regulation were performed on Dileptus anser. In this ciliate 2 body regions can be distinguished: proboscis and trunk. When a large portion of the trunk is excised, shape regulation occurs and the proper proboscis/trunk ratio is restored through elongation of the remnant of the trunk and shortening of the proboscis. When there is nothing but proboscis left, the trunk is formed from the proximal portion of proboscis and again the right proportion is restored. Regulation of the ciliary pattern is based mainly on resorption of some ciliary elements. The resorption of somatic ciliature is especially intense within narrowing regions, where otherwise overcrowding of cilia would occur. The resorption of oral ciliature was found to occur within an area located at the apex of the proboscis. Oral structures when damaged by cutting may be repaired in situ. Changes in the microfibrillar system of the cell were found during regulation of shape of the posterior region of the cell, as well as during regulation of size of oral structures. Regulatory processes in Dileptus are compared to those known for other ciliates, and possible differences between the regulation of shape and the regulation of pattern are discussed.

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