Aspects of Light in the Biology of Green Hydra

  • R. L. Pardy


A wide variety of cnidarians maintain algal symbionts within their tissues. These symbionts are photosynthetically active when illuminated and translocate large percentages of their photosynthetic products to the host (see Muscatine, 1974, for a comprehensive review). In addition to the light requirements for photosynthesis, the symbionts, like other plants, appear to have light requirements for cell division, cell development, and other processes. By altering light intensities, the wavelength of radiant energy and the duration of exposure (photoperiod), the experimenter can attempt to selectively manipulate some of the symbiont’s biology and thereby dissect or characterize subsystems functioning within the intact association. Using this strategy I have examined the effects of light on the green hydra symbiosis and have found that symbiont multiplication and ultrastructure exhibit a light dependency, and that high-intensity light may cause expulsion of symbionts. In terms of the physiology of the association, the light-dependent photosynthetic reactions may alter the association’s metabolic and respiratory processes. Finally, the light-stimulated and light-dependent processes of the symbiotic algae may be superimposed on the host’s normal light-sensitive behavior or phototaxis. What follows is a brief description of the green hydra symbiosis followed by a review of some recent work on the role of light in various aspects of the association ending with a description of current experiments on green hydra phototaxis.


Light Requirement Digestive Cell Symbiotic Alga Algal Symbiont Positive Phototaxis 
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.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Kanaev, I.I. 1952. Hydra: Essays on the Biology of Fresh Water Polyps. Soviet Academy of Sciences, Moscow.Google Scholar
  2. Muscatine, L. 1965. Symbiosis of hydra and algae. III. Extracellular products of the algae. Comp. Biochem. Physiol. 16: 77–92.PubMedCrossRefGoogle Scholar
  3. Muscatine, L. 1974. Endosymbiosis of cnidarians and algae. Pages 359–395 in: L. Muscatine and H.M. Lenhoff, Eds., 2. Academic Press, New York.Google Scholar
  4. Muscatine, L., and H.M. Lenhoff 1965. Symbiosis of hydra and algae. II. Effects of limited food and starvation on growth of symbiotic and aposymbiotic hydra. Biol. Bull. 129: 316–328.CrossRefGoogle Scholar
  5. Muscatine, L., C.B. Cook, R.L. Pardy, and R.R. Pool 1975. Uptake, recognition and maintenance of symbiotic Chlorella by Hydra viridis. Symp. Soc. Exp. Biol. 29: 175–203.PubMedGoogle Scholar
  6. Pardy, R.L. 1974. Some factors affecting the growth and distribution of the algal endosymbionts of Hydra viridis. Biol. Bull. 147: 105–118.PubMedCrossRefGoogle Scholar
  7. Pardy, R.L. 1976a. The morphology of green Hydra symbionts as influenced by host strain and host environment. J. Cell. Sci. 20: 655–669.PubMedGoogle Scholar
  8. Pardy, R.L. 1976b. The production of aposymbiotic hydra by the photodestruction of green hydra zoochlorellae. Biol. Bull, (in press).Google Scholar
  9. Pardy, R.L., and L. Muscatine 1973. Recognition of symbiotic algae by Hydra viridis. A quantitative study of the uptake of living algae by aposymbiotic H. viridis. Biol. Bull. 145: 565–579.CrossRefGoogle Scholar
  10. Pardy, R.L., and C. Dieckmann 1975. Oxygen consumption in the symbiotic hydra, Hydra viridis. Exp. Zool. 194: 373–378.CrossRefGoogle Scholar
  11. Pardy, R.L. and A.E. Heacox 1976. Growth of algal symbionts in regenerating hydra. Nature 260: 809–810.PubMedCrossRefGoogle Scholar
  12. Trembley, A. 1744. Mémoires pour servir à l’histoire d’un genre de polypes d’eau douce à bras en forme de cornes. Leyden, J. and H. VerbeckGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1976

Authors and Affiliations

  • R. L. Pardy
    • 1
  1. 1.Department of Developmental and Cell BiologyUniversity of CaliforniaIrvineUSA

Personalised recommendations