Nitrogen conservation and the green hydra symbiosis

The proportion of a natural population of green hydra containing food in their guts was very low (10%) and the calculated rate of holozoic feeding was comparable energetically to the rate of maltose release by the symbionts. It is suggested that the benefit to the host of maltose release by its symbionts is that it enables the host to divert amino acids from respiration and gluconeogenesis to protein synthesis and hence to conserve essential amino acids. Calculations show that the rate of maltose release by symbionts can account for the differences in the rates of host deamination between symbiotic and aposymbiotic animals.