Excretion of Sugars by <i>Chlorella</i> Species Capable and Incapable of Symbiosis with <i>Hydra viridis</i>

Abstract

Abstract The excretion of some sugars (maltose, glucose, and glucose‐6‐phosphate) was studied at pH 2.5–6.0 in 38 strains of Chlorella belonging to 15 species of which 7 are capable and 8 incapable of symbiosis with Hydra viridis . A high rate of maltose excretion below pH 4.0 (Cernichiari et al., 1969) was found only in C. vulgaris (non‐symbiotic) and C. mirabilis (non‐symbiotic). The other Chlorella species are characterized by quite different patterns of sugar excretion. C . spec. (= “ C. paramecii”; symbiotic) excretes very high amounts of maltose in the whole range from pH 2.5–6.0. C. kessleri (symbiotic), C. luteoviridis (symbiotic), and C. fusca var. fusca (non‐symbiotic) show a predominant excretion of glucose‐6‐phosphate from pH 2.5–6.0. Some strains also exhibit a high excretion of glucose above pH 4.0 ( C . spec. = “ C. paramecii ”) or below pH 3.0 ( C. fusca var. vacuolata ). Several species, e.g. C. saccharophila var. saccharophila (symbiotic), C. sorokiniana (non‐symbiotic), and C. protothecoides (symbiotic), excrete only very small amounts of sugars. There is no obvious correlation between sugar excretion and the ability or inability of the Chlorella species to form stable symbioses with Hydra viridis .