SYMBIOSIS OF HYDRA AND ALGAE. I. EFFECTS OF SOME ENVIRONMENTAL CATIONS ON GROWTH OF SYMBIOTIC AND APOSYMBIOTIC HYDRA

¹ Division of Marine Biology, Scripps Institution of Oceanography, University of California, San Diego, California
² Laboratory for Quantitative Biology, University of Miami, Coral Gables, Florida

1. Under controlled conditions in the laboratory, with daily feeding, Chlorohydra viridissima grew exponentially in a solution containing calcium, sodium, magnesium, potassium, chloride and bicarbonate ions. The optimum concentration of cations was ascertained and the effect of their deficiencies noted. The results are compared with data for Hydra littoralis and Cordylophora lacustris.

2. Calcium and sodium ions were required for growth. Magnesium and potassium enhanced growth and reproducibility of growth rates. Bicarbonate was not essential.

3. Both symbiotic and aposymbiotic C. viridissima grew at nearly identical rates, doubling in number every 1.45-1.90 days. In the absence of environmental sodium aposymbiotic hydra disintegrated several days sooner than normal green individuals, while growth of the latter was inhibited by high concentrations of calcium in the environment.