Just like an octopus, many other creatures can grow back a severed limb. Take, for example, the invertebrate we call the hydra. This freshwater creature measures less than an inch long and can regrow its severed head and body parts faster than you would think.
PBS recently posted a video to YouTube which shows off some hydras performing their distinctive regrowth trick. The video was a part of PBS' Deep Look series. Deep Look takes a look into various scientific topics using macro photography and microscopy.
Hydra is an entire genus of organisms that consists of small individuals that can heal themselves back to health. Their body consists of a thin, translucent column of cells with a closed lower end. It has an opening at its top end that both ingests food and ejects waste.
Around this dual-use opening is a circlet of anywhere from four to 25 tentacles.
Due to the hydra's abundance of stem cells, the organism can achieve "biological immortality". Stem cells are generic cells from which all other cells with specialized functions are generated.
When hydras lose one of their tentacles, their stem cells transform into the type needed to perform the tentacle's function. What's even more magical, the hydra can recover itself if somebody splits it in two. They can do this by using the stem cells to regrow two whole new bodies.
Scientists have been studying the magnificent abilities of the organism as they believe it may lead to better anti-ageing treatments. Adult humans each have a tiny number of stem cells as where the hydra's life building blocks make up half this organism's body.
Scientists are studying how hydra avoids ageing by using its stem cells to rebuild broken and old body parts. If scientists can find the answer, it is believed that the same process may apply to people. Perhaps, one day, with technology evolving, humans may be able to grow back their own limbs using their stem cells.