Plate Nº 64 · recorded October 10, 2026
Biology & EvolutionReported finding
Hydra loses immortality under cold, tied to taurine loss
A University of Innsbruck study maps how cold robs Hydra oligactis of its immortality, linking taurine loss, sex-specific metabolism, and massive cell death to the aging switch.
By Priya Raman3 min read600 words
In brief
- Hydra oligactis loses its immortality when exposed to cold, switching from asexual budding to sexual reproduction and eventually dying.
- The study, published in Aging Cell in 2026, was led by Nicki Marami-Zonouz and Ilse Kranner at the University of Innsbruck as part of the ARDRE doctoral program.
- Taurine levels dropped sharply during cold-induced aging; supplementing taurine partly reversed the transition to sexual reproduction.
- Uric acid spiked in aging hydras, suggesting massive apoptosis accompanies the production of sperm and eggs.
- Males and females showed distinct metabolic aging patterns, adding rare data on female biology.
The freshwater polyp Hydra oligactis can live essentially forever under ideal conditions. Cold changes that.
Exposure to low temperatures triggers a switch to sexual reproduction that ends the animal's immortality. A new study from the University of Innsbruck pinpoints a steep drop in taurine, an aminosulfonic acid also found in humans, as a central feature of that aging process.
The findings appear in a paper published in Aging Cell in 2026. The team, led by biologists Nicki Marami-Zonouz and Ilse Kranner as part of the ARDRE doctoral program, mapped the metabolites — small chemical compounds produced by cells — of hydras undergoing the transition from cloning to sexual reproduction.
What happens when hydras get cold?
Under optimal temperatures and feeding conditions, Hydra oligactis reproduces by budding — essentially cloning itself — and shows no measurable aging.
Cold acts as an environmental stress signal. The animal responds by producing sperm or eggs instead, an adaptation that lets embryos survive harsh alpine-lake winters.
The trade-off is fatal for the parent. Hydras that switch to sexual reproduction begin to age and eventually die. Other Hydra species keep their immortality even under stress, making Hydra oligactis unusual within its genus.
What did the metabolic profiles show?
The team analyzed the full suite of small molecules in aging hydras. A clear biochemical fingerprint emerged:
- Some metabolites rose steadily with age.
- Others fell steadily.
- A third group peaked as the animals reached sexual maturity.
The data also flagged a sex-specific pattern: males and females aged differently. The authors emphasized that female metabolism remains underrepresented in biomedical research more generally, and their data add to a thin literature.
Why does taurine matter?
The most striking single finding was a sharp decline in taurine, an aminosulfonic acid essential in both hydras and humans, as the animals progressed through cold-induced aging.
When researchers supplemented the hydras' environment with extra taurine, the animals showed an "anti-aging" response and partly reversed the transition toward sexual reproduction.
The hydra data echo results from mammals, where taurine levels also fall with age and supplementation extends healthy lifespan. That parallel is what excites co-author Bert Hobmayer of the Institute of Zoology.
"With the results of this study, we can for the first time link the aging of these primitive animals to the aging of vertebrates and humans — while also drawing a direct comparison with hydras, which are considered immortal," Hobmayer said. "Hydra oligactis is thus an exciting link between vertebrates and the hydras, which are significantly older in evolutionary terms."
What role does cell death play?
The metabolic profile also pointed to massive controlled cell death — apoptosis — as a prerequisite for making sperm and eggs.
Uric acid, a downstream byproduct of purine breakdown (purines are the chemical building blocks of DNA), surged in aging hydras, consistent with the molecular debris left behind by apoptosis.
How do hydras help aging research?
Hydra oligactis has a simple body built from a limited set of cell types, yet it shares much of its genetic makeup with vertebrates. The new findings strengthen the case for using the species as a model organism in fundamental aging research.
The study does not yet show that taurine loss causes aging in hydras, only that the two move together. Whether the same metabolic switch operates in mammals remains untested.
Still, the parallel is precise enough to guide new experiments. It also gives biologists a fresh foothold on a question that has long resisted simple answers.
Publication: Nicki Marami-Zonouz et al., "Metabolic Signatures of Aging and Gametogenesis in Hydra oligactis," Aging Cell (2026). DOI: 10.1111/acel.70643.
via Phys.org Biology (Source)
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Senior reporter covering industry trends and analytics at SciBeat.
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