Editing Crinoid (section)

===Reproduction and life cycle===
Crinoids are [[Dioecy|dioecious]], with individuals being either male or female. In most species, the [[gonad]]s are located in the pinnules but in a few, they are located in the arms. Not all the pinnules are reproductive, just those closest to the crown. The [[gamete]]s are produced in genital canals enclosed in genital coeloms. The pinnules eventually rupture to release the [[sperm]] and [[ovum|eggs]] into the surrounding sea water. In certain genera, such as ''[[Antedon]]'', the fertilised eggs are cemented to the arms with secretions from epidermal glands; in others, especially cold water species from Antarctica, the eggs are [[Egg incubation|brooded]] in specialised sacs on the arms or pinnules.<ref name=Ruppert/>

The fertilised eggs hatch to release free-swimming [[Echinoderm#Larval development|vitellaria larvae]]. The bilaterally symmetrical larva is barrel-shaped with rings of [[Cilium|cilia]] running round the body, and a tuft of sensory hairs at the upper pole. While both feeding (planktotrophic) and non-feeding (lecithotrophic) larvae exist among the four other extant echinoderm classes, all present day crinoids appear to be descendants from a surviving clade that went through a [[Population bottleneck|bottleneck]] after the [[Permian–Triassic extinction event|Permian extinction]], at that time losing the feeding larval stage.<ref>{{cite journal |doi=10.1038/sj.hdy.6800866 |pmid=16850040 |title=The active evolutionary lives of echinoderm larvae |journal=Heredity |volume=97 |issue=3 |pages=244–52 |year=2006 |last1=Raff |first1=R A |last2=Byrne |first2=M|doi-access=free }}</ref> The larva's free-swimming period lasts for only a few days before it settles on the bottom and attaches itself to the underlying surface using an adhesive gland on its underside. The larva then undergoes an extended period of [[metamorphosis|metamorphoses]] into a stalked [[Juvenile (organism)|juvenile]], becoming radially symmetric in the process. Even the free-swimming feather stars go through this stage, with the adult eventually breaking away from the stalk.<ref name=Ruppert/>

====Regeneration====
Crinoids are not capable of clonal reproduction as are some [[starfish]] and [[brittle star]]s, but are capable of regenerating lost body parts. Arms torn off by predators or damaged by adverse environmental conditions can regrow, and even the [[Organ (biology)|visceral mass]] can regenerate over the course of a few weeks.<ref name=Ruppert/> The stalk's uppermost segment and the basal plates have the capacity to regenerate the entire crown. Nutrients and other components from the stalk, especially the upper 5 cm, are used in crown regeneration.<ref name=AmemiyaOli>{{cite journal |last1=Amemiya |first1=Shonan |last2=Oji |first2=Tatsuo |title=Regeneration in sea lilies |journal=Nature |date=June 1992 |volume=357 |issue=6379 |page=546-547 |doi=10.1038/357546a0 |bibcode=1992Natur.357..546A |url=https://doi.org/10.1038/357546a0 |language=en |issn=1476-4687|url-access=subscription }}</ref>

Crinoids have been able to regenerate parts since Paleozoic times.<ref name=AmemiyaOli />  These regenerative abilities may be vital in surviving attacks by predatory fish.<ref name=Ruppert/>