Editing Hydra (genus) (section)

==Reproduction and life cycle==
[[File:Hydra Budding.svg|thumb|left|upright=1.35|''Hydra'' ''[[budding]]'': {{olist |Non-reproducing |Creating a bud |Daughter growing out |Beginning to cleave |Daughter broken off |Daughter [[Clone (cell biology)|clone]] of parent}}]]
Most hydra species do not have any gender system. Instead, when food is plentiful, many ''Hydra'' [[Asexual reproduction|reproduce asexually]] by [[budding]]. A section of the body wall and an extension of the digestive cavity develops, creating a bud.<ref name = mc/> The buds grow into miniature adults and break away when mature.

When a hydra is well fed, a new bud can form every two days.<ref>{{cite book |vauthors=Patton WK |chapter=Hydra (coelenterate) |title=Grolier Multimedia Encyclopedia. |publisher=Grolier Online |date=August 2014}}</ref> When conditions are harsh, often before winter or in poor feeding conditions, [[sexual reproduction]] occurs in some ''Hydra''. Swellings in the body wall develop into either ovaries or testes. The testes release free-swimming [[gamete]]s into the water, and these can fertilize the egg in the ovary of another individual. The fertilized eggs secrete a tough outer coating, and, as the adult dies (due to starvation or cold), these resting eggs fall to the bottom of the lake or pond to await better conditions, whereupon they hatch into nymph ''Hydra''. Some ''Hydra'' species, like ''[[Hydra circumcincta]]'' and ''[[Hydra viridissima]]'', are [[hermaphrodite]]s<ref>{{cite book |vauthors=Holstein T, Emschermann P |date=1995 |title=Cnidaria: Hydrozoa Süsswasserfauna von Mitteleuropa. Bd 1/2+ 3 |location=Stuttgart |publisher=Spektrum Akademischer Verlag |isbn=978-3-8274-0836-5}}</ref> and may produce both testes and ovaries at the same time.

Many members of the [[Hydrozoa]] go through a body change from a [[polyp (zoology)|polyp]] to an adult form called a [[Medusa (biology)|medusa]], which is usually the life stage where sexual reproduction occurs, but ''Hydra'' do not progress beyond the polyp phase.<ref>{{Cite book|author=Hickman, Cleveland P. Jr. |title=Integrated principles of zoology|year=2019|isbn=978-1-260-20519-0|edition=Eighteenth|location=New York, NY|oclc=1097367369}}</ref>