Fig. 4From: The cellular basis of bioadhesion of the freshwater polyp Hydra Transmission electron microscopy images of chemically and cryo-fixed Hydra polyps. a Longitudinal section through a chemically-fixed basal disc showing individual basal disc cells. Electron dense granules tend to accumulate at the aboral end of the cell, which is the area attaching to the substratum. At the aboral end, several cytoplasmic extensions are present [arrows]. b Cryo-fixed basal disc reveals the fine structure of secretory granules. c Chemically-fixed Hydra polyp right after attachment to the substratum. d Interface between an attached basal disc and the substratum. Note protruded cytoplasmic extensions are in contact with the substratum. Scale bars 10Â ÎĽm (a, c), 2Â ÎĽm (b), 5Â ÎĽm (d). Abbreviations: en, endoderm; m, mesoglea; bdc, basal disc cell; I, Hydra secretory granule I; II, Hydra secretory granule II; III, Hydra secretory granule III; IV, Hydra secretory granule IV; s, substratum; arrows, indicate cytoplasmic extensions; asterisks, indicate vacuoles of waterBack to article page