The ecology of a novel symbiosis between a marine peritrich ciliate and chemoautotrophic bacteria

A symbiosis between a sessile colonial ciliate, Zoothamnium niveum (HEMPRIC H & EHRENBERG, 1831), and chemolithoautotrophic bacteria oxidizing reduced sulfur compounds is described. The ciliates and their ectosymbionts occur o n mangrove pear in the Caribbean. The feather-shaped ciliate colonies expan d and contract, thus exposing the microbes alternately to oxygenated water above and sulfidic water within the boundary layer developed on the surface of the highly sulfidic peat. The symbiotic ciliates colonize sites with hi gh sulfide flux where the microbial surface mat has been disturbed and grow there until the microbe mat re-establishes itself.