Significance of the occurrence of chemoautotrophic bacterial endosymbionts in lucinid clams from Bermuda

Five species of lucinid clams from Bermuda (Codakia costata, Ctena orbiculata, Parvilucina multilineata, Lucina radians, Anodontiaphilippiana) had ribulose-1.5-bisphosphatecarboxylase activity in the gills.Presence of this enzyme of the Calvin-Benson cycle along with dark coloration of gills and morphologically simplified digestive tract strongly suggests presence of chemoautotrophic bacteria living symbiotically with the clams.Natural history is described for these 5 lucinids and several others not studied biochemically All inhabit reduced sediments rich in organic matter, where hydrogen sulfide is detectable.Results, along wlth previously published studies, indlcate that most clams of the family Lucinidae live symbiotically with chemoautotrophic bacteria in their gills and inhabit sulfide-rich environments.