ABSTRACT
A high diversity of thiotrophic symbioses is found in sulphide-rich marine habitats, involving several phyla of protists and invertebrates, as well as several subdivisions of the Proteobacteria. Whereas some of the better-known symbioses are highly evolved endosymbioses, the more primitive ectosymbioses are less well known. The sulphur-oxidising chemolithotrophic nature of the bacteria and their nutritive importance to the eukaryote host have been demonstrated for the ciliates
Kentrophoros
spp. and
Zoothamnium niveum
, the nematode subfamily Stilbonematinae, and the carid shrimp
Rimicaris exoculata
. For a number of other regular bacteria-eukaryote associations, such a symbiotic relationship has been hypothesised based on ecological, morphological, physiological or molecular data, but is still inconclusive.
