Editing Hectocotylus

{{short description|Cephalopod sex organ}}
[[File:Hectocotyle1.jpg|thumb|160px|[[Georges Cuvier]]'s original illustration of an octopus hectocotylus, which he named ''Hectocotyle octopodis'']]
A '''hectocotylus''' ({{plural form}}: '''hectocotyli''') is one of the [[cephalopod limb|arm]]s of male [[cephalopod]]s that is specialized to store and transfer [[spermatophore]]s to the female.<ref name="HanlonMessenger2018">{{cite book|author1=Roger T. Hanlon|author2=John B. Messenger|title=Cephalopod Behaviour|url=https://books.google.com/books?id=oppPDwAAQBAJ&q=hectocotylus|date=22 March 2018|publisher=Cambridge University Press|isbn=978-1-108-54674-4}}</ref> Structurally, hectocotyli are [[muscular hydrostat]]s. Depending on the species, the male may use it merely as a conduit to the female, analogously to a [[penis]] in other animals, or he may [[Autotomy|wrench it off]] and present it to the female.

The hectocotyl arm was first described in [[Aristotle's biology|Aristotle's biological works]]. Although [[Aristotle]] knew of its use in mating, he was doubtful that a tentacle could deliver sperm. The name ''hectocotylus'' was devised by [[Georges Cuvier]], who first found one embedded in the mantle of a female [[Argonaut (animal)|argonaut]]. Thinking it to be a [[helminths|parasitic worm]], in 1829 Cuvier gave it a [[name of a biological genus|generic name]] (''Hectocotyle''),<ref>{{cite book|author-link=Armand Marie Leroi|author=Leroi, Armand Marie|title=The Lagoon: How Aristotle Invented Science|date=25 September 2014|publisher=Penguin |isbn=9780698170391|url=https://books.google.com/books?id=-DVBAwAAQBAJ&q=aristotle+hectocotylus&pg=PT80}}</ref><ref>{{cite book|author-link=D'Arcy Wentworth Thompson|author=Thompson, D'Arcy Wentworth|year=1913|title=On Aristotle as a biologist, with a prooemion on Herbert Spencer|series=Being the [[Herbert Spencer]] Lecture before the University of Oxford, on February 14, 1913|publisher=Oxford University Press|page=19}}</ref><ref>{{cite book|author1=Nixon M.|author2-link=John Zachary Young|author2=Young J.Z.|year=2003|url=https://books.google.com/books?id=BRvrtsuKc6MC&q=hectocotylus|title=The brains and lives of Cephalopods|publisher=Oxford University Press|isbn=9780198527619}}</ref><ref>{{cite web|url=https://www.gbif.org/species/3246735|title=GBIF:Hectocotylus Cuvier, 1829|access-date=21 November 2016}}</ref>
which is a New Latin term combining the Greek words for "hundred" (''hec(a)to(n)'') and for "hollow thing, cup" (''[[cotyle]]'').

== Structure ==
Generalized anatomy of squid and octopod hectocotyli:
{{multiple image
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==Variability==
Hectocotyli are shaped in many distinctive ways, and vary considerably between species. The shape of the tip of the hectocotylus has been much used in [[octopus]] [[systematics]].

* Many [[Coleoidea|coleoids]] lack hectocotyli altogether.<ref name=ToL /> 
* Among [[Decapodiformes]] (ten-limbed cephalopods), generally either one or both of arms IV are hectocotylized.
* In [[Incirrina|incirrate]] octopuses, it is one of arm pair III.<ref name=ToL>Young, R.E., M. Vecchione & K.M. Mangold (1999). [http://tolweb.org/accessory/Cephalopoda_Glossary?acc_id=587 Cephalopoda Glossary]. [[Tree of Life Web Project]].</ref> Rare examples of double and bilateral hectocotylization have also been recorded in incirrate octopuses.<ref>Robson, G.C. 1929. On a case of bilateral hectocotylization in ''Octopus rugosus''. ''Journal of Zoology'' '''99'''(1): 95–97. {{doi|10.1111/j.1469-7998.1929.tb07690.x}}</ref><ref>Palacio, F.J. 1973. {{cite web|url= https://archive.org/details/nautilus87amer |title=On the double hectocotylization of octopods. |year=1973 |publisher=Melbourne, Fla., etc., American Malacologists, inc., etc. }} ''The Nautilus'' '''87''': 99–102.</ref>
* In male [[seven-arm octopus]]es (''Haliphron atlanticus''), the hectocotylus develops in an inconspicuous sac in front of the right eye that gives the male the appearance of having only seven arms.
* In [[Argonaut (animal)|argonauts]], the male transfers the spermatophores to the female by putting its hectocotylus into a cavity in the [[mantle (mollusc)|mantle]] of the female, called the ''pallial cavity''. This is the only contact the male and female have with each other during [[copulation (zoology)|copulation]], and it can be at a distance. During copulation, the hectocotylus breaks off from the male. The [[funnel–mantle locking apparatus]] on the hectocotylus keeps it lodged in the pallial cavity of the female.

===Table of hectocotyli===
{| class="wikitable"
!width= | Illustration
!width= | Species
!width= | Family
|-
| [[File:Abraliopsis morisi hectocotylus-English.jpg|250px<!--upright image, to equalize image sizes-->]]
| ''[[Abraliopsis morisi]]''
| [[Enoploteuthidae]]
|-
| [[File:Argonauta bottgeri hectocotylus-2.jpg|300px]]
| ''[[Argonauta bottgeri]]''
| [[Argonautidae]]
<!--|-
| [[File:Hectocotyle1-2.jpg|300px]]
| ?
| ?-->
|-
| [[File:Bathypolypus arcticus hectocotylus-2.jpg|300px]]
| ''[[Bathypolypus arcticus]]''
| [[Octopodidae]]
|-
| [[File:Graneledone verrucosa hectocotylus.jpg|300px]]
| ''[[Graneledone verrucosa]]''
| [[Octopodidae]]
|-
| [[File:Haliphron atlanticus hectocotylus.jpg|300px]]
| ''[[Haliphron atlanticus]]''
| [[Alloposidae]]
|-
|[[File:Ocythoe tuberculata hectocotylus.jpg|300px]]
| ''[[Ocythoe tuberculata]]''
| [[Ocythoidae]]
|-
| [[File:Scaeurgus patagiatus hectocotylus-2.jpg|300px]]
| ''[[Scaeurgus patagiatus]]''
| [[Octopodidae]]
|-
| [[File:Tremoctopus violaceus5.jpg|200px<!--upright image, to equalize image sizes-->]]
| ''[[Tremoctopus violaceus]]''
| [[Tremoctopodidae]]
|-
| [[File:Uroteuthis duvauceli hectocotylus.jpg|300px]]
| ''[[Uroteuthis duvauceli]]''
| [[Loliginidae]]
|}

== References ==
{{Commons category|Hectocotylus}}
{{Reflist}}

{{Cephalopod anatomy}}

[[Category:Cephalopod zootomy]]
[[Category:Sex organs]]
[[Category:Animal male reproductive system]]