Editing Platypus (section)

=== Venom ===
{{Main|Platypus venom}}
[[File:Platypus spur.JPG|right|thumb|The calcaneus spur on the male's hind limb is used to inject venom.]]

While both male and female platypuses are born with back ankle spurs, only the males' deliver venom.<ref>{{cite web |url=http://www.australianfauna.com/platypus.php |title=Australian Fauna |publisher=Australian Fauna |access-date=14 May 2010 |url-status=dead |archive-url=https://web.archive.org/web/20120529040439/http://www.australianfauna.com/platypus.php |archive-date=29 May 2012 }}</ref><ref>{{cite web |url=http://www.usyd.edu.au/news/84.html?newsstoryid=2267 |title=Platypus venom linked to pain relief |publisher=University of Sydney |date=8 May 2008 |access-date=14 May 2010 |archive-date=21 August 2011 |archive-url=https://web.archive.org/web/20110821151157/http://www.usyd.edu.au/news/84.html?newsstoryid=2267 |url-status=live }}</ref><ref>{{cite web |url=http://rainforest-australia.com/platypus_poison.htm |title=Platypus poison |publisher=Rainforest Australia |access-date=14 May 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100529165453/http://rainforest-australia.com/platypus_poison.htm |archive-date=29 May 2010 }}</ref>
It is powerful enough to kill smaller animals such as dogs, and though it is not lethal to humans, it can inflict weeks of agony.<ref name="PS" /><ref>Weimann, Anya (4 July 2007) [https://web.archive.org/web/20121105043922/http://www.cosmosmagazine.com/news/1423/evolution-platypus-venom-revealed Evolution of platypus venom revealed]. ''[[Cosmos (magazine)|Cosmos]]''.</ref> [[Edema]] rapidly develops around the wound and gradually spreads through the affected limb, and it may develop into an excruciating [[hyperalgesia]] (heightened sensitivity to pain) persisting for days or even months.<ref name="JN">{{cite journal |author=de Plater, G.M. |author2=Milburn, P.J. |author3=Martin, R.L. |year=2001 |title=Venom From the Platypus, ''Ornithorhynchus anatinus'', Induces a Calcium-Dependent Current in Cultured Dorsal Root Ganglion Cells |journal=Journal of Neurophysiology |volume=85 |issue=3 |pages=1340–5 |doi=10.1152/jn.2001.85.3.1340 |pmid=11248005 |s2cid=2452708 }}</ref><ref name="venom">{{cite web |title=The venom of the platypus (''Ornithorhynchus anatinus'') |url=http://www.kingsnake.com/toxinology/old/mammals/platypus.html |url-status=dead |archive-url=https://web.archive.org/web/20120201185504/http://www.kingsnake.com/toxinology/old/mammals/platypus.html |archive-date=1 February 2012 |access-date=13 September 2006}}</ref>

The venom is composed largely of [[defensin]]-like [[protein]]s (DLPs) produced by the immune system, three of which are unique to the platypus.<ref name="PS">{{cite journal| last = Gerritsen| first = Vivienne Baillie| title = Platypus poison| journal = Protein Spotlight| issue = 29| date = December 2002| url = http://www.expasy.org/spotlight/back_issues/sptlt029.shtml| access-date = 14 September 2006| archive-date = 20 October 2008| archive-url = https://web.archive.org/web/20081020054110/http://www.expasy.org/spotlight/back_issues/sptlt029.shtml| url-status = live}}</ref> In other animals, defensins [[lysis|kill]] pathogenic bacteria and viruses, but in platypuses they are also collected into a venom against predators. Venom is produced in the [[wikt:crural|crural]] glands of the male, which are kidney-shaped [[alveolar gland]]s connected by a thin-walled duct to a [[calcaneus]] spur on each hind limb. The female platypus, in common with echidnas, has rudimentary spur buds that do not develop (dropping off before the end of their first year) and lack functional crural glands.<ref name="ABRS" /> Venom production rises among males during the breeding season, and it may be used to assert dominance.<ref name="PS" />

Similar spurs are found on many archaic mammal groups, indicating that this was an ancient general characteristic among mammals.<ref>Jørn H. Hurum, Zhe-Xi Luo, and Zofia Kielan-Jaworowska, 
Were mammals originally venomous?, Acta Palaeontologica Polonica 51 (1), 2006: 1–11</ref>