Archivory in hypersaline aquatic environments: haloarchaea as a dietary source for the brine shrimp Artemia.

Archaea have been the most overlooked and enigmatic of the three domains of life for decades. Knowledge of key ecological interactions, such as trophic links between this domain and higher level organisms, remains extremely limited. The co-occurrence of halophilic Archaea (haloarchaea) and the non-selective filter feeder, brine shrimp Artemia under the unique ecological characteristics of hypersaline aquatic environments, constitutes an excellent opportunity to further unravel the ecological role of the Archaea domain as a source of food to zooplankton metazoans. In the present study, we combine the use of haloarchaea biomass assimilation experiments using 13C isotope as tracer, with gnotobiotic Artemia culture tests using haloarchaea mono-diets, to investigate potential trophic links between the organisms. Our results demonstrated the ability of Artemia to assimilate nutrients from mono-diets of haloarchaea biomass in order to survive and grow, providing clear indications that archivory may occur in hypersaline aquatic environments. Additionally, our study highlights the use of stable isotopes labelling as a potential tool to further disentangle the specific pathways by which archaeal cellular constituents are digested by consumers.