Loading...
Initial language selection is based on your web browser preferences.
Hydras belong to Cnidarians so their body plan is quite simple. their body is filled with a cavity (gastrovascular cavity) used for digestion. The cavity has only one opening used for feeding as well as disposing undigestible parts. Due to the absence of any rigid structures, hydras can inflate their body volume quite significantly and are, therefore, able to digest a prey twice as large as their own body. Entire process of digestion lasts usually from two to three days. Their respiration and excretion systems are totally absent. Excretion happens anywhere through epidermis. Nervous system is diffused which means that it is made of interconected cells that are spread evently and connect photoreceptors and touch-sensitive cells localised in the body wall and tentacles. Hydras are very capable to regenerate a body part that is injured or missing.
Some species are vivid green. It is not caused by a pigment, instead the green colour comes from green algae living in their cells. It is mutually beneficial relationship. Algae gain a safe place to live and hydras can use the products of algae´s photosystesis.
