Here, a few notes on the study of sea anemones, among which are examples of negligibly senescent species. These are comparatively rare species in which individuals do not seem to suffer the effects of degenerative aging, or where they do it is considerably less pronounced than in their near relatives. In lower animals the degree to which individual immortality is possible in principle appears to be greater. The continual and highly proficient regeneration of the sort seen in lower animals such as hydras and anemones, in which every body part can be regrown from a remnant, falls by the wayside somewhere on the way to the evolution of a complex brain and central nervous system, however. It remains an open question as to what of use to medicine can be learned from the study of the biochemistry of negligibly senescent species that are very distant from us:
Sea anemones are soft bodied animals that attach themselves to rocks and coral reefs in shallow waters. There are more than 1,000 species of anemone, varying in size from a few centimetres to more than a metre across. They live in every ocean, from the warmest to the coldest. "As far as we know, these are immortal animals. They live a very long time - one was documented to have lived 100 years. They don't have old age. They live forever and proliferate, just getting bigger." If you cut off their tentacles, they grow new ones. Even if you cut off their mouths they grow new "heads." As long as they are not poisoned or eaten, as is often the case, they seem to go on and on.
They appear to avoid ageing and the adverse effects that humans experience over time. "You should see tumours in these animals, but we have very few descriptions of that. They are constantly replenishing themselves without getting cancer." Instead of ageing, anemones seem to stay young and fully functioning. "If I look at a sea anemone today and compare it to a week later the same structure will be there but many of the cells will have been replaced." How it does this isn't clear. "We would love to be able to find a gene or pathway that allows it to avoid ageing. Sea anemones are the simplest animals we know of that have a nervous system - it's not organised in the same way as ours, but they do have a network of neurons that allows them to respond to stimuli and be very active predators. Genetically, sea anemones share a lot with us. We found a lot of similarities we had not seen when comparing humans to fruit flies or nematodes."