The freshwater hydra, whose mortality risk changes little with age, lacks <i>Klotho</i> and <i>NAMPT</i>, two genes often studied in the biology of aging
The freshwater hydra, whose mortality risk changes little with age, lacks Klotho and NAMPT, two genes often studied in the biology of aging
On August 26, 2026, Genome Biology and Evolution published a study in which the authors assembled the genome, the complete set of DNA, of the freshwater hydra Hydra vulgaris and compared three laboratory strains with the closely related Hydra oligactis. Laboratory observations showed that mortality risk in H. vulgaris changed little with age. In H. oligactis, sexual reproduction and cooling to 10 °C trigger aging. The comparison identified differences that can now be tested experimentally.
Hydra attracted the attention of aging researchers after long-term demographic observations. In a 2015 study, researchers monitored 2 256 animals from 12 groups, including clones more than 41 years old. Mortality remained extremely low and constant, while fertility showed no systematic decline. A model developed by Bégi and Hadany identified the conditions under which selection can maintain mortality that rises very little with age. The hydra H. oligactis provided an informative comparison because sexual reproduction and cooling to 10 °C trigger aging in this closely related species.
The authors assembled the genome of the H. vulgaris AEP.JNIG strain into 15 chromosomes and combined data from three laboratory strains. Strains maintained through asexual reproduction for long periods diverge genetically. Using data from three strains reduces the risk of mistaking gaps in a single genome assembly for a feature of the entire species.
Both species retain most of the basic systems associated with aging, including DNA repair, the removal of damaged cellular components, mitochondrial energy production, and stem-cell maintenance. The authors identified 12 groups of related genes that were present in the aging H. oligactis but absent from all three H. vulgaris strains. These included Klotho and NAMPT, which are often studied in the biology of aging. Five groups found only in H. vulgaris also occur in 29 other species, so they are less likely to explain its unusual aging pattern.
The comparison also identified differences in genes involved in the synthesis of ATP and related molecules that participate in energy metabolism. The new strain has more methyl marks, chemical modifications of DNA, within evolutionarily conserved genes. Their abundance was associated with more stable transcription of these genes into RNA and fewer RNA transcripts originating outside the usual transcription regions.
Further experiments can test how differences in energy metabolism and gene regulation relate to the fact that aging begins in one hydra, while mortality risk in the other changes little with age.