A novel facultative mutualistic relationship between bufonid tadpoles and flagellated green algae

.—Variable environments can produce intolerable conditions for certain species. In some cases, survival is assured byfortuitous mutualistic interactions. We show that the critical thermal maximum (CTM) for Bufo tadpoles is increased whenthe green alga Chlorogonium aggregates on their skins in warm ephemeral pools. The congregation of Chlorogonium may havebeen a response toward a source of otherwise limiting CO2, reciprocally providing O2 to the stressed tadpoles. Such arelationship has not been reported previously for these organisms.