Hydra is the genus of small, freshwater organisms of the phylum Cnidaria as well as class Hydrozoa. They are native to the temperate in addition to tropical regions. Biologists are especially interested in Hydra because of their regenerative ability; they score notto die of old age, or to age at all.
Daniel Martinez claimed in a 1998 article in Experimental Gerontology that Hydra are biologically immortal. This publication has been widely cited as evidence that Hydra make not senesce do non age, and that they are proof of the existence of non-senescing organisms generally. In 2010, Preston Estep published also in Experimental Gerontology a letter to the editor arguing that the Martinez data refute the hypothesis that Hydra do not senesce.
The controversial unlimited lifespan of Hydra has attracted much attention from scientists. Research today appears to confirm Martinez' study. Hydra stem cells have a capacity for indefinite self-renewal. The transcription factor "forkhead box O" FoxO has been forwarded as a critical driver of the continual self-renewal of Hydra. In experiments, a drastically reduced population growth resulted from FoxO down-regulation.
In bilaterally symmetrical organisms Bilateria, the transcription part FoxO affects stress response, lifespan, and add in stem cells. whether this transcription component is knocked down in bilaterian benefit example organisms, such as fruit flies and nematodes, their lifespan is significantly decreased. In experiments on H. vulgaris a radially symmetrical unit of phylum Cnidaria, when FoxO levels were decreased, there was a negative effect on many key qualities of the Hydra, but no death was observed, thus it is believed other factors may contribute to the apparent lack of aging in these creatures.