TEM observations of holotrich nematocysts in catch tentacles of the sea anemone Haliplanella luciae reveal that capsule wall formation occurs by means of a self-assembly of proteins from a Golgi-derived pool within the capsule interior. Wall growth results from precipitation of material onto the wall, as indicated by an increase in wall thickness throughout development. Wall maturation is characterized by wall thinning. Such thinning was reversed by performic acid treatment, suggesting that disulfide bond formation within the wall causes thinning. Nematocyst thread walls stain with the sulfur stain, alcian blue, both before and after performic acid treatment, while capsule walls are stained only after such treatment, suggesting that the thread has "free" sulfur groups that are absent from the capsule. / Occurring simultaneous with wall development, is a Golgi-deposition of calcium into the developing nematocyst, as evidenced by potassium pyroantimonate deposits in the Golgi and nematocyst interior that were removed by EGTA. Tube inversion is accompanied by an apparent increase in antimonate concentration within the nematocyst, along with an increase in fluids in the cytoplasm, suggesting that a dehydration of nematocyst contents occurs at the time of tube inversion. / The mature nematocyst moves to the cell surface (in preparation for discharge) by apparent microtubule disassembly between the capsule and dense bodies located at the cell surface. / Nematocyst discharge begins with the opening of the capsule tip apical flaps. The flaps are sealed by subunit-lined seams that separate upon discharge, suggesting that the subunits hold the flaps together. / The everted thread is lined on both sides by subunits that might bind together to hold the uneverted thread in its folded configuration. Thread eversion could follow subunit uncoupling. / Nematocyst discharge is accompanied by a calcium-mediated contraction of supporting cell microfilament bundles. Such contraction causes the capsule to become recessed beneath these bundles, possibly anchoring the capsule in the tentacle. Because extracellular fibrous network connections occur between the cnidocyte cell surface and the supporting cell stereocilia, it was proposed that supporting cell contraction (which changes supporting cell shape) might initiate nematocyst discharge. / Source: Dissertation Abstracts International, Volume: 44-10, Section: B, page: 3013. / Thesis (Ph.D.)--The Florida State University, 1983.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75195 |
| Contributors | WATSON, GLEN M., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 124 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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