Stolons, hyperplastic stolons and the polyp-stolon junctions.

<p>(A) Projection of phalloidin stained gastrozooid, showing longitudinal muscle fibers and circular muscle fibers, the hydrorhiza from which the polyp emanates, and the location of the chloe. Note that polyp-stolon junction is a simple aperture, lacking specialized valves. (B) A portion of the hydrorhiza showing continuity of axial muscle fibers at two stolonal junctions. Differential interference contrast, grey, axial muscle fibers stained with phalloidin, red, and nuclei, DAPI stained in blue. (C) Projection of polyp stolon junction at the chloe showing longitudinal muscle strands of gastrozooid labeled with phalloidin, red, and mesoglea labeled with antibodies specific for <i>Hydra</i> collagen IV, green. Note that longitudinal muscle strands do not traverse mesoglea. (D) Projection of two hyperplastic stolons, labeled with phalloidin, red. The perisarc, blue, was visualized by autofluorescence. Note extensive meshwork of F-actin rings at tip. (E) Depth coded projection of phalloidin stained stolon at region proximal to the stolon tip, showing F-actin rings of the basal ectodermal cells where they adhere to the substratum (see also Figs. 4A,D) and gastrodermal axial muscle fibers. (F) Depth coded projection of phalloidin stained stolonal tip showing terminus of gastrodermal axial muscle strands and F-actin rings at stolonal tip. (E, F) Color code: red ca. 0–2 µm from substratum; orange 3–6 µm, yellow-green 7–10 µm, blue >10 µm. Optical depth, number of sections: (A) 27 µm, 14; (C) 8 µm, 10; (D) 40 µm, 10; (E) 17 µm, 43; (F) 18 µm, 25. (A–F) Scale: 20 ∶m. AX, axial muscle fibers; CO, opening of chloe; CM, circular muscle fibers; FAR, F-actin ring; GZ, gastrozooid; H, hydrorhiza; HP, hyperplastic stolons; LM, longitudinal muscle fibers, M, mesoglea, P, perisarc.