I picked this little guy because he was innocent enough. Sorta looked like a sweet Christmas ornament… maybe. Well, don’t read on if you’re using one of these at the top of your tree this year.
Biologists are especially interested in Hydra because of their regenerative ability – they appear not to age or die of old age.
Now how they eat, it’s sorta like that old 1979 movie that Ridley Scott made…
When feeding, Hydra extend their body to maximum length and then slowly extend their tentacles. Despite their simple construction, the tentacles of Hydra are extraordinarily extensible and can be four to five times the length of the body. Once fully extended, the tentacles are slowly manoeuvred around waiting for contact with a suitable prey animal. Upon contact, nematocysts on the tentacle fire into the prey, and the tentacle itself coils around the prey. Within 30 seconds, most of the remaining tentacles will have already joined in the attack to subdue the struggling prey. Within two minutes, the tentacles will have surrounded the prey and moved it into the opened mouth aperture. Within ten minutes, the prey will have been enclosed within the body cavity, and digestion will have started. Hydra is able to stretch its body wall considerably in order to digest prey more than twice its size. After two or three days, the indigestible remains of the prey will be discharged by contractions through the mouth aperture.
Read more about the Hydra on Wikipedia, oh and, Merry Christmas!