Editing Echinoderm (section)

===Asexual reproduction===
{{See also|#Regeneration}}
[[File:Comet form of Linckia.png|thumb|upright|'Comet' form of ''[[Linckia]]'']]

One species of [[seastar]], ''[[Ophidiaster granifer]]'', reproduces asexually by [[parthenogenesis]].<ref name="Yamaguchi1984">{{harvnb|Yamaguchi|Lucas|1984}}</ref> In certain other [[asterozoa]]ns, adults reproduce asexually until they mature, then reproduce sexually. In most of these species, asexual reproduction is by [[transverse fission]] with the disc splitting in two. Both the lost disc area and the missing arms regrow, so an individual may have arms of varying lengths.<ref name=Fisher1925/><ref>{{harvnb|McGovern|2002}}</ref> During the period of regrowth, they have a few tiny arms and one large arm, and are thus often known as "comets".<ref name=Hotchkiss2000/><ref name="Monks1904">{{harvnb|Monks|1904}}</ref>

Adult sea cucumbers reproduce asexually by transverse fission. ''[[Holothuria parvula]]'' uses this method frequently, splitting into two a little in front of the midpoint. The two halves each regenerate their missing organs over a period of several months, but the missing genital organs are often very slow to develop.<ref name="Kille1942">{{harvnb|Kille|1942}}</ref>

The larvae of some echinoderms are capable of asexual reproduction. This has long been known to occur among starfish and brittle stars, but has more recently been observed in a sea cucumber, a sand dollar and a sea urchin.<ref name="Eaves2003">{{harvnb|Eaves|Palmer|2003}}</ref> This may be by [[Fragmentation (reproduction)|autotomising]] parts that develop into secondary larvae, by [[budding]], or by [[paratomy|splitting transversely]]. Autotomised parts or buds may develop directly into fully formed larvae, or may pass through a [[gastrula]] or even a [[blastula]] stage. New larvae can develop from the preoral hood (a mound like structure above the mouth), the side body wall, the postero-lateral arms, or their rear ends.<ref name=Eaves2003/><ref name="Jaeckle1994">{{harvnb|Jaeckle|1994}}</ref><ref name="Vaughn2009">{{harvnb|Vaughn|2009}}</ref>

Cloning is costly to the larva both in resources and in development time. Larvae undergo this process when food is plentiful<ref name="McDonald2010">{{harvnb|McDonald|Vaughn|2010}}</ref> or temperature conditions are optimal.<ref name=Vaughn2009/> Cloning may occur to make use of the tissues that are normally lost during metamorphosis.<ref name="Vaughn2008">{{harvnb|Vaughn|Strathmann|2008}}</ref> The larvae of some sand dollars clone themselves when they detect dissolved fish mucus, indicating the presence of predators.<ref name=Vaughn2009/><ref name=Vaughn2008/> Asexual reproduction produces many smaller larvae that escape better from planktivorous fish, implying that the mechanism may be an anti-predator adaptation.<ref name="Vaughn2010">{{harvnb|Vaughn|2010}}</ref>