Euplotes uncinatus (Ciliophora, Hypotrichia), a new species with zooxantellae

Abstract

During the observations of a field collection of Maristentor dinoferus with fluorescence microscopy, we discovered a smaller ciliate with zooxanthellae. On the basis of morphological, morphometric and ultrastructural characters, this ciliate has been recognized as a new species of the genus Euplotes. To emphasize the peculiar shape and extension of the right buccal margin, the species has been named Euplotes uncinatus sp. n. The most distinctive traits of E. uncinatus are the presence of mucocyst-like vesicles, a kind of extrusome not previously found in Euplotes, and the presence of zooxanthellae. Evidence from ciliate behavior and zooxanthellae ultrastructure make it very likely that the zooxanthellae are symbiotic, even though some are evidently consumed by the host