Zoospore chemotaxis of mangrove thraustochytrids from Hong Kong

Zoospores of mangrove isolates of Schizochytrium mangrovei KF6, KF7, KF12 (three strains), Thraustochytrium striatum KF9 and Ulkenia sp. KF13 were examined for their chemotactic responses to amino acids, carbohydrates, ethanol, and leaf extracts using a capillary root model. Most leaf extracts of mangrove plants and a marsh grass tested were shown to induce moderate chemotactic responses in zoospores of both S. mangrovei KF6 and Ulkenia sp. KF13. Of the remaining amino acids and carbohydrates evaluated, glutamic acid and pectin induced strong attraction in zoospores of S. mangrovei KF6 and Ulkenia sp. KF13, suggesting these are the major components in leaves which may be responsible for the chemotactic response of thraustochytrid zoospores in nature. Zoospores of T striatum KF9, in general, showed a weak chemotactic response to all the tested compounds and extracts except cellulose, which elicited a moderate response. The ecological significance of the data presented is discussed.