Formation of Polysaccharides by Hydra from Substrates produced by their Endosymbiotic Algae

Abstract

THE exact ways in which endosymbiotic algae serve their host tissues have been the subject of much research in the past 10 years. The view that the algae contribute to the nutrition of the host has gained much support from studies using radioactive tracers. Algae were shown to contribute material labelled with carbon-14 when the co-elenterate host (anemone¹, coral² or hydra³) was exposed to ¹⁴CO₂ in the light. Muscatine has shown that algae isolated from hydra⁴ and from other freshwater invertebrates⁵ leak ¹⁴C-maltose into the media. The questions remain whether the algae release glucose or maltose in vivo, and in what way do the hydra utilize these compounds. We describe here experiments which show that the animal tissue of Chlorohydra viridissima incorporates a large proportion of the small molecules produced by their endosymbiotic algae during photosynthesis, and that most of these small molecules are converted by hydra into polysaccharide.