A novel bioenergetic model outlines the metabolism of a deep-sea clam and that of its sulfur-oxidizing symbionts

For the first time, two Dynamic Energy Budget (DEB) models were developed for a chemosymbiotic deep-sea vesicomyid clam. A classical DEB model was applied and then an innovative DEB model was developed (named "farming"). The models were parameterized using data on host and symbionts, including original unpublished data. In the farming model the digestion of the sulfur-oxidizing bacterial symbionts for host nutrition was explicitly modeled. Unexpected results were obtained regarding the dynamics of host and symbionts with this model: the host appears to forgo a maximal ingestion for a lower and stable ingestion, revealing a new kind of homeostasis. Moreover, when the clam is adult, most of the oxygen consumed by the chemosynthetic symbiosis was predicted to be by the symbionts. A high host energy maintenance flux was predicted and consistent with the likely high energy demand of host ion homeostasis mechanisms to cope with symbiont protons and sulfates release.