Colloblast

Colloblasts are unique, multicellular structures found in ctenophores.[1] They are widespread in the tentacles of these animals and are used to capture prey. Colloblasts consist of a collocyte containing a coiled spiral filament, internal granules and other organelles.[2]

Like the cnidocytes of cnidarians, colloblasts are discharged from the animals’ tentacles, and are used to capture prey. However, unlike cnidocytes, which are venomous cells, colloblasts contain adhesives which stick to, rather than sting the prey.

Form and Function

Colloblasts were first described in 1844.[3]

Colloblasts are mainly composed of two cells types, the stalk itself, which is divided into the collosphere and collopod, as well as numerous cap cells that deposit external secretion granules on the surface of the collosphere.[1] These granules, also called eosinophilic granules, are thought to be the source of adhesion.[4]A spiral filament is wrapped around the collopod, which is attached to the tentilla via a negatively charged root.[5]

When disturbed, the plasma bridge connecting the spiral filament to the collopod breaks, releasing the colloblast from the tentilla of the ctenophore.[5] On contact with prey, external secretion granules on the apical side of the collosphere rupture, releasing an adhesive substance. The spiral filament absorbs the impact of the rupture, preventing the ensnared prey from escaping.[6]

Occurrence

Colloblasts are found in all ctenophores except those of the order Beroida, which lack tentacles, and the species Haeckelia rubra, which use cnidocytes from cnidarian prey.[6]

References

  1. ^ a b Leonardi, N..D.; Thuesen, E.V.; Haddock, S.H.D. (2020). "A sticky thicket of glue cells: A comparative morphometric analysis of colloblasts in 20 species of comb jelly (Phylum Ctenophora)". Ciencias Marinas. 46 (4): 211–225. doi:10.7773/cm.v46i4.3118.
  2. ^ Harrison, Frederick W.; Kohn, Alan J. (1996-12-06). Microscopic Anatomy of Invertebrates, Mollusca II. ISBN 978-0-471-15447-1.
  3. ^ Mari-Luz, Hernandez-Nicaise (1984). "9.7: The integument of the tentacles: the colloblast". In Bereiter-Hahn, Jürgen; Matoltsy, A. Gedeon; Richards, K. Sylvia (eds.). Biology of the Integument Invertebrates. Berlin, Heidelberg: Springer. p. 107. ISBN 9783642515934.
  4. ^ Franc, J.-M. (1978). "Organization and function of ctenophore colloblasts: An ultrastructural study". Biological Bulletin. 155 (3): 527–541. doi:10.2307/1540788. JSTOR 1540788.
  5. ^ a b Von Byern, J.; Mills, C.E.; Flammang, P. (2010). "3: Bonding Tactics in Ctenophores — Morphology and Function of the Colloblast System". In Von Byern, Janek; Grunwald, Ingo (eds.). Biological Adhesive Systems. New York City, NY: SpringerWienNewYork. p. 29. ISBN 978-3-7091-0141-4.
  6. ^ a b Pang, K.; Martindale, M.Q. (2008). "Comb jellies (ctenophora): A model for basal metazoan evolution and development". Cold Spring Harbor Protocols. 2008 (12). pdb.emo106. doi:10.1101/pdb.emo106. PMID 21356709.
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