Freshwater hydra is a typical representative of coelenterates living in lakes, ponds and river backwaters. The first to see and describe the hydra was A. Levenguk, the inventor of the microscope and a renowned naturalist.
Freshwater hydra structure
This freshwater polyp looks like a short, gelatinous and translucent tube the size of a grain, surrounded by a corolla of 6-12 tentacles. There is a mouth opening at the front end of the body, the rear end of the hydra tapers into a long leg with a sole at the end. A full hydra is about 5 mm long, a hungry one is much longer.
Nutrition and lifestyle
Freshwater hydra feeds on cyclops, daphnia, mosquito larvae and fish fry. It attaches itself to plants with its sole and slowly sways, moving its long tentacles in all directions, looking for prey. The tentacles are covered with sensitive cilia, when touched, a stinging thread is emitted, paralyzing the victim.
The prey is pulled by the tentacle to the mouth opening and is absorbed. Having digested the swallowed, hydra throws out the remains of digestion through the same hole. With a successful hunt, this small predator can absorb an enormous amount of food, several times its volume. Having a translucent body, hydra takes on the color of the food eaten and is red, green or black.
Reproduction of freshwater hydra
With good nutrition, freshwater hydra quickly begins budding (asexual reproduction). The buds grow from a small tubercle to a fully formed individual in a few days. At first, young hydras are connected to the mother's body, but after the formation of the sole, they separate and begin their independent life. Hydra buds usually in summer.
When it gets cold or in unfavorable conditions (hunger), hydras reproduce by eggs that form in the outer layer of the body. A ripe egg is covered with a strong shell and falls to the bottom of the reservoir. After the formation of eggs, the old individual usually dies. Reproduction with eggs is called sexual reproduction. That is, in the life of a freshwater hydra, both methods of reproduction are replaced.
Freshwater Hydra Regeneration
Hydras have an amazing ability to regenerate. If an individual is cut into two parts, then tentacles and a sole will grow very quickly in each. There are known experiments carried out by the Dutch zoologist Tremblay, in which he managed to get new hydras from the smallest pieces and even spliced halves of different hydras together. As modern studies have shown, such restoration of tissues and organs is provided by animal stem cells.
