• Zoothamnium nireum;
  • Ciliophora;
  • Peritrichida;
  • sulfur bacteria;
  • symbiosis;
  • mangal

Abstract. A symbiosis between a sessile colonial ciliate, Zoothamnium niveum HEMPRICH & EHRENBERG. 1831. and chemolithoautotrophic bacteria oxidizing reduced sulfur compounds is described. The ciliates and their ectosymbionts occur on mangrove peat in the Caribbean. The feather-shaped ciliate colonies expand 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 symbioticciliates colonize sites with high sulfide flux where the microbial surface mat has been disturbed and grow there until the microbe mat re-establishes itself.