Editing Sea urchin (section)

=== Anti-predator defences ===
[[File:Flower urchin by Vincent C Chen.jpg|thumb|The [[flower urchin]] is a dangerous, potentially lethally venomous species.]]

The [[spine (zoology)|spines]], long and sharp in some species, protect the urchin from [[predator]]s. Some tropical sea urchins like [[Diadematidae]], [[Echinothuriidae]] and [[Toxopneustidae]] have venomous spines. Other creatures also make use of these defences; crabs, shrimps and other organisms shelter among the spines, and often adopt the colouring of their host. Some crabs in the [[Dorippidae]] family carry sea urchins, starfish, sharp shells or other protective objects in their claws.<ref name=Thiel>{{cite book|author1=Thiel, Martin|author2=Watling, Les|title=Lifestyles and Feeding Biology |url=https://books.google.com/books?id=RZ-eBgAAQBAJ&pg=PA200 |year=2015 |publisher=Oxford University Press |isbn=978-0-19-979702-8 |pages=200–202}}</ref>

[[Pedicellaria]]e<ref>{{cite web |url=http://www.nhm.ac.uk/research-curation/research/projects/echinoid-directory/intro/defence3.html |title=Defence – pedicellariae |author=<!--Staff writer(s); no by-line.--> |website=Echinoid Directory |publisher=[[Natural History Museum, London|Natural History Museum]] |access-date=2014-08-04 |archive-date=2014-10-06 |archive-url=https://web.archive.org/web/20141006072057/http://www.nhm.ac.uk/research-curation/research/projects/echinoid-directory/intro/defence3.html |url-status=live }}</ref> are a good means of defense against ectoparasites, but not a panacea as some of them actually feed on it.<ref>Hiroko Sakashita, " Sexual dimorphism and food habits of the clingfish, Diademichthys lineatus, and its dependence on host sea urchin ", Environmental Biology of Fishes, vol. 34, no 1, 1994, p. 95–101</ref> The hemal system defends against endoparasites.<ref>{{cite journal |url=https://link.springer.com/content/pdf/10.1007%252FBF01989305.pdf |title=Diseases of echinoderms |journal=Helgoländer Meeresuntersuchungen |volume=37 |issue=1–4 |pages=207–216 |author=Jangoux, M. |year=1984 |access-date=23 March 2018 |bibcode=1984HM.....37..207J |doi=10.1007/BF01989305 |s2cid=21863649 |doi-access=free |archive-date=29 October 2020 |archive-url=https://web.archive.org/web/20201029002716/https://link.springer.com/content/pdf/10.1007%252FBF01989305.pdf |url-status=live }}</ref>