CARBON EXCHANGE BETWEEN POLYSIPHONIA-LANOSA (RHODOPHYCEAE) AND ITS BROWN ALGAL HOST

Polysphonia lanosa and its preferred Ascophyllum nodosum host exchange C-14-labeled photoassimilates. Exchange was demonstrated by injecting C-14-bicarbonate into air bladders on 15-30 cm cultured sections of f ield-collected host blades. Each section bore rhizoidally attached Pol ysiphonia. In a separate set of experiments, Polysiphonia on similar h ost material was surface treated with C-14-bicarbonate in sealed vesse ls. Movement of radioactive label was detected by autoradiographic and liquid scintillation techniques. On average, 10.5% of total label mov ed from host to hemiparasite following the first treatment. and 9.7% m oved from hemiparisite to host following the second. Reciprocal exchan ge of tagged photoassimilates may play an important role in the specif icity of thr relationship between these two algal species.