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Respiratory Gas Exchange in Ascidans: An Almost Diffusion Limited Animal with a Cardiovascular System

  • M. McCabe
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 200)

Abstract

The ascidians are a class of the sub Phylum Tunicata, and part of the Phylum Chordata. Characteristically they are sessile marine organisms which have a motile larval stage. They are believed to represent an ancient stock from which other chordates and eventually the vertebrates have evolved. The geometry of the motile (larval) stage and of the ancestral animal is simple in the extreme, supporting the view that this species represents a very early and fundamental form in the evolution of animals. Berrill (1955) has discussed this aspect of the ascidians and has pointed out the evolutionary increase in body size which has occured, from an original animal of less than one mm length, to present day organisms of 10 cm or more. The appearance of a tunic being seen as an adaptation to provide mechanical support and protection for this increased body. The archaic form was a typical diffusion limited animal, whereas it is by no means so obvious that this is so for modern much larger organisms, which possess a cardiovascular system, although rather an unusual one in which the heart regularly and rythmically reverses the direction of flow of blood.

Keywords

Apparent Diffusion Coefficient Hyaluronic Acid Fundamental Form Partial Specific Volume Reversible Oxygen 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Agudelo, I., Kustin, K. and Robinson, W., 1982. Blood chemistry of Boltenia ovifera. Comp. Biochem. Physiol. 72A, 161.Google Scholar
  2. Baldwin, D., McCabe, M. and Thomas, F., 1984. The respiratory gas carrying capacity of ascidian blood. Comp. Biochem. Physiol. 79A, 479.Google Scholar
  3. Berrill, N.J., 1955. In “The Origin of Vertebrates”, p 25. Clarendon Press, Oxford.Google Scholar
  4. Carlisle, D.B., 1968. Vanadium and other metals in ascidians. Proc. Roy. Soc. ( Lond.) B, 171, 31.Google Scholar
  5. Eyring, H., 1941. In “The Theory of Rate Processes” ed. S. Laidler, H. Eyring. and S. Glasstone, p 477. McGraw-Hill, New York.Google Scholar
  6. Laurent, T.C., Bjork, I., Pietruszkiewicz, A. and Persson, H., 1963. On the interaction between polysaccharides and other macromolecules: Transport of globular particles through hyaluronic acid solution. Biochem. Biophys. Acta 78, 351.Google Scholar
  7. Laurent, T.C., Preston, B.N., Pertoft, H., Gustafsson, B. and McCabe, M., 1975. Diffusion of linear polymers in hyaluronate solution. Eur. J. Biochem. 53, 129.Google Scholar
  8. MacDougall, J.D.B. and McCabe, M., 1967. Diffusion coefficient of oxygen through tissues. Natures 215, 1173.CrossRefGoogle Scholar
  9. Senozan, N.M., 1974. Vanadium in the living world. J. Chem. Educ. 51, 505.Google Scholar
  10. Wittenberg, J.B., 1970. Myoglobin facilitated oxygen diffusion: role of myoglobin in oxygen entry to muscle. Physiol Revs. 50, 559.Google Scholar

Copyright information

© Plenum Press, New York 1986

Authors and Affiliations

  • M. McCabe
    • 1
  1. 1.Department of BiochemistryJames Cook University of North QueenslandAustralia

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