Feeding
Hydra mainly feed on small aquatic invertebrates such as Daphnia and Cyclops.
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.
The feeding behaviour of Hydra demonstrates the sophistication of what appears to be a simple nervous system.
Some species of Hydra exist in a mutual relationship with various types of unicellular algae. The algae are protected from predators by Hydra and, in return, photosynthetic products from the algae are beneficial as a food source to Hydra.
Read more about this topic: Hydra (genus)
Famous quotes containing the word feeding:
“The will to domination is a ravenous beast. There are never enough warm bodies to satiate its monstrous hunger. Once alive, this beast grows and grows, feeding on all the life around it, scouring the earth to find new sources of nourishment. This beast lives in each man who battens on female servitude.”
—Andrea Dworkin (b. 1946)
“I am still a learner, not a teacher, feeding somewhat omnivorously, browsing both stalk and leaves; but I shall perhaps be enabled to speak with more precision and authority by and by,—if philosophy and sentiment are not buried under a multitude of details.”
—Henry David Thoreau (1817–1862)
“Man may have his opinion as to the relative importance of feeding his body and nourishing his soul, but he is allowed by Nature to have no opinion whatever as to the need for feeding the body before the soul can think of anything but the body’s hunger.”
—George Bernard Shaw (1856–1950)