The differentiation of cytoskeletal structures in nematocytes of Hydra

Nematocytes of hydra feature a complex cytoskeleton consisting mainly of several bundles of actin filaments and a basket-like structure formed by microtubules. The aim of this study was to establish the sequence of appearance of cytoskeletal elements during nematocyte development using immuno-fluorescence and electron microscopical techniques. Our results are a first step in trying to understand developmental hierarchies and mechanisms which govern the synthesis and assembly of the cytoskeleton in nematocytes. The finger-shaped rods around the apex of the capsule are the first detectable elements of the cytoskeleton. Microtubules of the basket structure then follow and later, the actin filaments of microvilli which support the cnidocil. The actin filaments, however, do not show the highly ordered bundling pattern characteristic of filaments in functional nematocytes.