title: Pattern formation in ciliary organelle systems of ciliated protozoa.
abstract: Genetic, morphometric, and microsurgical investigations of the pattern of ciliary organells in ciliate protozoa support the view that ther are two types of developmental process responsible for the positioning of these organelles.  The first is exemplified by the propagation of ciliary rows through localized addition of new ciliary units along the axis of the row, a process which is responsible for the maintenance of the pre-existing number of rows in clonal lineages over a large number of fissions.  The second is illustrated by two examples: (1) Ciliary units are distributed among ciliary rows of Euplotes minuta according to an invariant geometrical pattern that is independent both of the total number of units and of the number of rows.  (2) Microsurgical alteration of the topographical contours of a related ciliate, Paraurostyla weissei, brings about a shift in the sites of formation of certain specific ciliary rudiments to new positions that are determined in relation to the newly constructed form.  The two modes of pattern formation in ciliates are discussed from both genetic and developmental viewpoints.  The localized positional mechanisms within the ciliary rows allow for a 'configurational heredity' shich is, however, subject to constraints of nuclear genic control both of the stable range of number of rows and of the positioning mechanism itself.  The large-scale systems of pattern determination are probably more closely related to the field properties of developing multicellular organisms.  In ciliates such systems are almost certainly located in the cell membrane or in the relatively fixed cytoplasmic layer just beneath the membrane.
mesh_terms: D000818:Animals; D002455:Cell Division; D002923:Cilia / Q000648:ultrastructure*; D016798:Ciliophora / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure*; D003227:Conjugation, Genetic; D014644:Genetic Variation; D005827:Genetics, Microbial; D008846:Micromanipulation; D008954:Models, Biological