Replication of basal bodies and ciliogenesis in a ciliated epithelium of the lamprey.

Replication of basal bodies (centrioles) replication and ciliogenesis were followed in the neck segment of the tubular nephron during stage 3 of metamorphosis in the sea lamprey, Petromyzon marinus L. Procentrioles are formed through both centriolar and acentriolar pathways. In the acentriolar pathway, dense granules, initially formed at or near the Golgi apparatus, become closely associated with all developing procentrioles and may provide precursors required for centriole development. Both cylindrical structures and dense bodies are seen in this region and are likely formed from the coalescence of dense granules. Either dense bodies or mature centrioles become the central element in a generative complex from which procentrioles arise. After maturation of the procentrioles into basal bodies, they migrate to the apical surface of the cell where they align themselves and develop a ciliary axoneme from their distal end. There are fundamental similarities in the mechanism of basal body replication during development of a ciliated epithelium in all vertebrates so far examined.