The morphogenesis of nematocytes in Hydra and Forsklia: An ultrastructural study

https://doi.org/10.1016/S0022-5320(81)80085-8Get rights and content

The morphogenesis of nematocytes in Hydra attenuata and Forsklia sp. involves the complex processes of capsule formation, growth, and differentiation; establishment of nematocyst thread regions within the external tube and invagination; development of pericentriolar processes and the cnidocil-associated apparatus; and the differentiation of the armament and operculum. Several important morphological questions are clarified in the present ultrastructural study. Throughout all stages of capsule development, including the earliest one observed, the two main structural layers, sklera and propria, are present in addition to the unit membrane. The external tube structure is directly proportional to the mature nematocyst thread and is encircled by a basket of microtubules the number of which is also dependent on size. The microtubules seem to be nucleated by the pair of centrioles or its pericentriolar processes. The wall of the external tube consists of three layers and the controversial invagination process is shown to be actually a modified invagination since only the middle layer invaginates. Nematocyte development overall is characterized by a close correlation between the formation of the nematocyst and the formation of the sensory apparatus.

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