Metabolic rates and thermal tolerances of chemoautotrophic symbioses from Lau Basin hydrothermal vents and their implications for species distributions

Metabolic rates and thermal tolerances of three species of mobile symbiotic molluscs (two provannid gastropods Alviniconcha sp. and Ifremeria nautilei; and the mussel Bathymodiolus brevior) from Lau Basin hydrothermal vents were measured. Thermal tolerances of the two gastropods were similar and well in excess of temperatures observed in situ, although Alviniconcha sp. appeared to have slightly higher tolerances. B. brevior had lower thermal limits that could exclude it from central areas of active venting. High-pressure respirometry experiments revealed that Alviniconcha sp. has very high potential growth rates; its uptake of carbon for its endosymbionts being among the highest recorded. Uptake rates of metabolites in I. nautilei and B. brevior were an order of magnitude lower than those observed in Alviniconcha sp. Taken together, these thermal tolerances and metabolite uptake rates help to explain the zonation patterns seen in situ, where Alviniconcha sp. is found closest to the source of vent fluid, followed by I. nautilei, and then B. brevior.