Hydractinia echinata are tiny organisms that can be found living on the back of hermit crabs in the waters around Ireland. What makes these guys so interesting is they have an amazing ability to re-generate any lost body parts (they can even re-generate a new head should its head be bitten off by a predator!) This regeneration ability, it has been discovered is a result of the Hydractinia having so many stem cells in its body.
The team led by Dr. Uri Frank in NUI Galway have been able to show that how the stem cells of the Hydractinia behave are very similar to their human counterparts which makes them a very interesting organism to study so we can better understand human development, aging and disease. Using these tiny creatures could open doors for scientists in ways that could not have been imagined before.

- ‘Immortal’ Irish marine animal provides hope for research into ageing (irishtimes.com)
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Hydractinia can be found in Irish waters and are a perfect organism to study stem cells