Acid Phosphatase Content And Acidity Of The Perialgal Vacuole Of Ephydatia muelleri

Freshwater sponges containing symbiotic algae can serve as a model for the study of relationships in which a host and an intracellular symbiont benefit. In freshwater sponges, symbiotic algae belonging to the genus, Chlorella, are housed in large cytoplasmic vacuoles, called perialgal vacuoles. I used microscopic techniques in an effort to determine whether the perialgal vacuoles ofthe freshwater sponge, Ephydatia muelleri, (1) contain active acid phosphatase, a lysosomal enzyme and (2) are acidic. Whereas the postcoupling method for localizing active acid phosphatase gave equivocal results, the Gomori method for localizing the enzyme revealed that few of the perialgal vacuoles possesed active enzyme. The fluorescence of LysoSensor pH-sensitive probes suggested that the perialgal vacuoles are not strongly acidic and may have a pH of between -5.5 and —8.0. The latter conclusion is considered tentative, however, since the precise location of the fluorescing LysoSensor probe within the perialgal vacuoles could not be ascertained