Is Hydra really immortal?

Overall, a clear biochemical fingerprint of aging emerged, as evidenced by the hydra's metabolic profile. Some metabolic products increased steadily during the aging process, others decreased steadily, and still others peaked when the animals reached sexual maturity.

There were clear differences between male and female animals—a fact that the study authors particularly emphasized, since data on female metabolism are still underrepresented in biomedical studies.

Another striking finding was the decline in taurine—an aminosulfonic acid that is also essential for humans—as the hydras aged. Taurine supplementation, however, triggered an "anti-aging process" in the hydras that reversed the transition to sexual reproduction.

The findings on Hydra oligactis thus fit into the broader picture of aging research. It has already been shown in mammals that taurine levels decline with age and that supplementation can extend healthy lifespan.

The metabolic profile also indicated that the production of sperm and egg cells is accompanied by massive controlled cell death—known as apoptosis. Biochemically, this is reflected in a dramatic increase in uric acid, a byproduct of purine degradation that can be a downstream consequence of apoptosis.