Hydra sp. trying and failing to stun and eat a cladoceran (water flea). 40x magnification. Darkfield microscopy.

Hydra is a genus of freshwater cnidarian (class Hydrozoa). Other cnidarians include jellyfish, corals, anemones, siphonophores, and many more. Hydras are radially symmetrical and have two tissue layers in their body. They also have a nerve net, which is a simple version of a nervous system, and their tentacles have cells called cnidocytes that secrete stinging chemicals used to stun their prey. Hydras are really charismatic animals and if you find one, you’ll be able to see it expand and contract depending on what’s around it and sometimes they look like they’re just dancing and doing weird things. Hydras reproduce asexually by budding, which is when an identical hydra grows out of the parent and will detach when it is mature enough to live and reproduce on its own. Many scientists are interested in hydras because they don’t really age and will continue living until eaten or exposed to deadly conditions and they can very quickly and efficiently regenerate damaged tissue. Learning the mechanisms behind those two processes would be really interesting and potentially helpful in the future to understand the process of mammalian aging and in biomedical applications of wound healing and tissue regeneration.