Summary
The flame cells of common fresh-water planarians are cyrtocytes similar in basic structure and function to the protonephridial end-organs in other phyla. They function as ultrafilters for intercellular fluid and are shaped like an elongate basket containing the ciliary flame. Thin regions of the basket wall are fenestrated by groups of parallel slits. The slits are 350 Å wide and (viewed en face) appear to be bridged by 55 Å filaments spaced at 200 Å intervals. Under varied conditions of fixation, these filaments are most similar to the filaments associated with the glycocalyx coating the luminal surface of the cell. The possible involvement of the preserved elements with the “filtration membrane” is discussed.
Thicker cytoplasmic columns or ribs containing 220 Å diameter microtubules support the thin regions of the basket wall and are the base for radial processes which prevent adjacent cells from occluding the fenestrae. Rapidly cooling the worm from room temperature to 2°C results in a short term reduction in the number of microtubules seen in the basket ribs. However this number has returned to normal after one minute in the cold, and by five minutes a greaterthan-normal number of microtubules is present which has been confirmed to be present after 3 days at 2°C. If microtubule subunits are hydrophobically bonded, these results suggest a metazoan control of such bonding which has not yet been demonstrated for protozoans.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Bennett, H. S.: Morphological aspects of extracellular polysaccharides. J. Histochem. Cytochem. 11, 14–23 (1963).
Brandenburg, J.: Die Reusenformen der Cyrtocyten. Eine Beschreibung von fünf weiteren Reusengeisselzellen und eine vergleichende Betrachtung. Zool. Beitr. 12, 345–417 (1966).
Braun, G., G. Kümmel, and J. A. Mangos: Studies on the ultrastructure and function of a primitive excretory organ, the protonephridium of the rotifer Asplanchna priodonta. Pflügers Arch. ges. Physiol. 289, 141–154 (1966).
Clark, A. W.: Microtubules in some unicellular glands of two leeches. Z. Zellforsch. 68, 568–588 (1965).
Ericsson, J. L. E.: Fine structural basis for hemoglobin filtration by glomerular capillaries. Nephron 5, 7–23 (1968).
Fawcett, D. W.: Cilia and flagella. In: The Cell (J. Brachet and A. E. Mirsky, eds.), vol. II, p. 217–297. New York: Academic Press 1961.
Gibbons, I. R.: The relationship between the fine structure and direction of beat in gill cilia of a lamellibranch mollusc. J. Biophys. biochem. Cytol. 11, 179–205 (1961).
Graff, L. V.: In: Bronn's Klassen und Ordnungen des Tier-Reichs, 4. Ic. II. Leipzig: C. F. Winter 1912–1917.
Hyman, L. H.: The Invertebrates, vol. II. New York: McGraw-Hill Book Co. 1951.
Iijima, I.: Untersuchungen über den Bau und die Entwicklungsgeschichte der Süßwasser-Dendrocoelen (Tricladen). Z. wiss. Zool. 40, 359–464 (1884).
Ito, S.: The enteric surface coat on cat intestinal microvilli. J. Cell Biol. 27, 475–491 (1965).
Kümmel, G.: Das Terminalorgan der Protonephridien, Feinstruktur und Deutung der Funktion. Z. Naturforsch. 13b, 677–679 (1958).
—: Die Feinstruktur der Terminalzellen (Cyrtocyten) der Priapuliden. Z. Zellforsch. 62, 468–484 (1964).
—, u. J. Brandenburg: Die Reusengeisselzellen (Cyrtocyten). Z. Naturforsch. 16b, 692–697 (1961).
Lang, A.: Der Bau von Gunda segmentata und die Verwandtschaft der Plathelminthen mit Cölenteraten und Hirudineen. Mitt. Zool. Stat. Neapel 3, 187–252 (1881).
MacRae, E. K.: The fine structure of sensory receptor processes in the auricular epithelium of the planarian, Dugesia tigrina. Z. Zellforsch. 82, 479–494 (1967).
McKanna, J. A.: Fine structure of the protonephridial system in planaria. II. Ductules, collecting ducts, and osmoregulatory cells. (In press) (1968).
Pedersen, K. J.: Studies on the nature of planarian connective tissue. Z. Zellforsch. 53, 569–608 (1961).
—: Some observations on the fine structure of planarian protonephridia and gastrodermal phagocytes. Z. Zellforsch. 53, 609–628 (1961).
Pontin, R. M.: The osmoregulatory function of the vibratile flames and the contractile vesicle of Asplanchna (Rotifera). Comp. Biochem. Physiol. 17, 1111–1126 (1966).
Roth, L. E.: Electron microscopy of mitosis in amebae. III. Cold and urea treatments: A basis for tests of direct effects of mitotic inhibitors on microtubule formation. J. Cell Biol. 34, 47–59 (1967).
Tilney, L. G., and K. R. Porter: Studies on microtubules in helizoa. II. The effect of low temperature on these structures in the formation and maintenance of the axopodia. J. Cell Biol. 34, 327–343 (1967).
Wetzel, B. K.: Contributions to the cytology of Dugesia tigrina (Turbellaria) protonephridia. Fifth int. congr. for electron microscopy. Q 10 1962.
Wilhelmi, J.: Untersuchungen über die Excretionsorgane der Süßwassertricladen. Z. wiss. Zool. 80, 544–575 (1906).
Author information
Authors and Affiliations
Additional information
This investigation was supported by NIH Pre-doctoral Training Grant 5T1 GM 723-07.
The author is grateful for the interest and guidance of Dr. Orin M. Lofthus and Dr. David B. Slautterback; and is pleased to acknowledge the generous support of undergraduate research by the President and Fellows of Carleton College, Northfield, Minnesota which made possible the initial stages of this work.
Rights and permissions
About this article
Cite this article
McKanna, J.A. Fine structure of the protonephridial system in planaria. Z. Zellforsch. 92, 509–523 (1968). https://doi.org/10.1007/BF00336662
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00336662