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Apical surface of hydrozoan nematocytes: Structural adaptations to mechanosensory and exocytotic functions
Author(s) -
Golz Rainer
Publication year - 1994
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1052220106
Subject(s) - nematocyst , cnidocyte , biology , cytoskeleton , microbiology and biotechnology , apical cell , microtubule , ultrastructure , microfilament , mechanosensitive channels , anatomy , biophysics , organelle , membrane , cell , ecology , biochemistry , receptor , coral , ion channel , cnidaria , genetics
At the apical cell pole of the nematocytes of a hydrozoan ( Hydra vulgaris ), cytoskeletal elements of different molecular families (microfilaments, microtubules, cross‐striated rootlets) are combined in a complex framework. As determined by transmission and scanning electron microscopy, the stimulus‐transducing cnidocil apparatus of these mechanosensitive cells is forced into a lateral position, facilitating the close apposition of the nematocyst to the apical cell membrane. The nematocyst, a single, extraordinarily large, exocytotic organelle, is held in position by a microtubular basket. The cnidocil apparatus and microtubular basket are linked to an ellipsoid arrangement of pseudovilli, i.e., small surface protrusions containing cross‐striated rods. These nematocyte‐specific, cytoskeletal elements mediate the anchorage of the entire cytoskeletal framework to the apical cell membrane. The apical membranes of the nematocyte and nematocyst are separated by a distance of only ∼ 50 nm. Structural modifications on the external side of the cyst membrane resemble those of synaptic membranes. © 1994 Wiley‐Liss, Inc.