Editing Overhand knot (section)

==In nature==
As a defensive measure, [[hagfish]]es, which resemble [[eel]]s, produce large volumes of thick [[Mucus|slime]] when disturbed. A hagfish can dislodge large quantities of slime on its skin, which it uses to evade predation, by tying its own body into an overhand knot, then sliding the knot from its head down to the tail. This action scrapes the slime off the fish's body. Hagfish also tie their bodies into overhand knots in order to create leverage to rip off chunks of their prey's flesh, but do so "in reverse" (starting at the tail, and sliding the knot towards the head for mechanical advantage).<ref>{{cite book |last1= Helfman |first1= Gene |last2= Collette |first2= Bruce B. |last3= Facey |first3= Douglas E. |last4= Bowen |first4= Brian W. |date= 2009-04-03 |title= The Diversity of Fishes: Biology, Evolution, and Ecology |edition= 2nd |url= https://books.google.com/books?id=FyehAR6hsUUC&pg=PA235 |publisher= Wiley–Blackwell |pages= 234–236 |isbn= 978-1-4051-2494-2 }}</ref>