Range: Cosmopolitan Habitat: Ponds, lakes, and slow flowing streams and rivers Size: Less than 1 inch (2.54cm) long Diet: Crustaceans like copepods, fish and insect larvae, and more Threats: Larger animals, temperature change, and pollution Life span: Unknown; Theoretically immortal

Transcript:

Today on Animal Fact Files we’re talking about hydras. There have been a few instances on this show where the distinction between plant and animal seems blurred, and today’s subject is no exception. Hydras are animals that are classified in the Hydra genus. Currently the number of living species is unknown, though they’re believed to number in the dozens at least. The hydra body is made up of a foot, a trunk, and a head. The foot is a disc shape that holds the hydra in place, the tubular trunk is most of the body in which digestion occurs among other processes, and the head is the mouth which is surrounded by tentacles. These tentacles are used for gathering food which we’ll be discussing shortly.

If you’ve seen our episode on coral this body shape might look familiar to you. This is a coral polyp. Hydras are also polyps. In fact, hydras are where the word “polyp” originated in modern zoology. A polyp is one of the general body shapes for all Cnidarians. In the case of most hydrozoans, polyps come together to form a colony organism, such as the Portuguese man of war; but in the case of hydras, these animals do not form colonies: they live on their own.

Hydras are freshwater animals and can be found throughout the world. They are most abundant in ponds, lakes, and slow flowing streams and rivers. Hydras are often referred to as sessile, but this is slightly misleading. An example of a sessile animal is a christmas tree worm; it’s an animal that has anchored itself in place and typically is unable to move from that place. While hydras do anchor themselves to vegetation and other surfaces in a body of water, they can move about if the need arises. A hydra can creep along a surface using its tentacles; it can also cartwheel by placing its tentacles on the surface and flinging its entire body around; it can also move along like an inchworm. It was actually this ability of movement that had the scientists who first discovered hydras second guessing their potential identity as plants!

Hydras are able to regenerate lost parts of their bodies. If cut in half, two new, genetically identical individuals will develop. Even if cut into small pieces, each piece will reform as long as the right cells are present! These animals also regenerate their bodies approximately every month. In essence, hydras are immortal - or at least they don’t age - or at least no studies have been able to prove otherwise as of this recording. Of course, they can die. Hydras may be eaten by larger animals. They can also perish if exposed to extremes like temperature, poor water quality, and more. They just don’t get “old”.

Hydras are small animals usually less than an inch (2.54cm) in length which means they also eat small animals. Crustaceans like copepods, fish and insect larvae, and basically anything the size of the hydra or smaller may end up on the hydra’s menu. Hydras are also Cnidarians - like jellyfish - which means they come equipped with stinging cells to neutralize prey. Some hydra stinging cells act like harpoons and spear a prey item, while others act like lassos and hold the prey in place as it is drawn to the hydra’s mouth.

Hydras are able to reproduce both sexually and asexually. Under normal circumstances, hydras reproduce asexually by budding. Budding is when an animal develops a clone of itself which will eventually detach from the parent’s body. When facing harsh conditions, however, hydras may reproduce sexually by releasing sperm which will fertilize the eggs of another hydra.

For more facts on hydra check out the links in the description. Thank you to alterego for today’s request! Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files.