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Hectocotylus

Cephalopod sex organ

Summary

Cephalopod sex organ

[[Georges Cuvier]]'s original illustration of an octopus hectocotylus. Mistaking it for its own separate organism, he named it ''Hectocotyle octopodis''.

A hectocotylus (: hectocotyli) is one of the arms of male cephalopods that is specialized to store and transfer spermatophores to the female. Structurally, hectocotyli are muscular hydrostats. 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 wrench it off and present it to the female.

The hectocotyl arm was first described in 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. Thinking it to be a parasitic worm, in 1829 Cuvier gave it a generic name (Hectocotyle), 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:

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 coleoids lack hectocotyli altogether.
Among Decapodiformes (ten-limbed cephalopods), generally either one or both of arms IV are hectocotylized.
In incirrate octopuses, it is one of arm pair III. Rare examples of double and bilateral hectocotylization have also been recorded in incirrate octopuses.
In male seven-arm octopuses (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 argonauts, the male transfers the spermatophores to the female by putting his hectocotylus into a cavity in the mantle of the female, called the pallial cavity. This is the only contact the male and female have with each other during 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

Illustration	Species	Family
[[File:Abraliopsis morisi hectocotylus-English.jpg	250px]]	Abraliopsis morisi	Enoploteuthidae
[[File:Argonauta bottgeri hectocotylus-2.jpg	300px]]	Argonauta bottgeri	Argonautidae
[[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]]	Tremoctopus violaceus	Tremoctopodidae
[[File:Uroteuthis duvauceli hectocotylus.jpg	300px]]	Uroteuthis duvauceli	Loliginidae

References

(22 March 2018). "Cephalopod Behaviour". Cambridge University Press.
Leroi, Armand Marie. (25 September 2014). "The Lagoon: How Aristotle Invented Science". Penguin.
Thompson, D'Arcy Wentworth. (1913). "On Aristotle as a biologist, with a prooemion on Herbert Spencer". Oxford University Press.
(2003). "The brains and lives of Cephalopods". Oxford University Press.
"GBIF:Hectocotylus Cuvier, 1829".
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]].
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
(1973). "On the double hectocotylization of octopods.". Melbourne, Fla., etc., American Malacologists, inc., etc..

Wikipedia Source

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cephalopod-zootomy sex-organs animal-male-reproductive-system

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