Hectocotylus

 ( Cephalopod Zootomy ) 

A hectocotylus (: hectocotyli) is one of the cephalopod limb of male that is specialized to store and transfer 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 Autotomy 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 helminths, in 1829 Cuvier gave it a generic name ( Hectocotyle),

(2025). 9780198527619, Oxford University Press. . ISBN 9780198527619

which is a New Latin term combining the Greek words for "hundred" ( hec(a)to(n)) and for "hollow thing, cup" ( cotyle).

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Structure Generalized anatomy of squid and octopod hectocotyli:

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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 lack hectocotyli altogether.
• Among Decapodiformes (ten-limbed cephalopods), generally either one or both of arms IV are hectocotylized.
• In Incirrina octopuses, it is one of arm pair III.Young, R.E., M. Vecchione & K.M. Mangold (1999). Cephalopoda Glossary. Tree of Life Web Project. Rare examples of double and bilateral hectocotylization have also been recorded in incirrate octopuses.Robson, G.C. 1929. On a case of bilateral hectocotylization in Octopus rugosus. Journal of Zoology 99(1): 95–97. Palacio, F.J. 1973. The Nautilus 87: 99–102.
• 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.

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Table of hectocotyli

	Abraliopsis morisi	Enoploteuthidae
	Argonauta bottgeri	Argonautidae
	Bathypolypus arcticus	Octopodidae
	Graneledone verrucosa	Octopodidae
	Haliphron atlanticus	Alloposidae
	Ocythoe tuberculata	Ocythoidae
	Scaeurgus patagiatus	Octopodidae
	Tremoctopus violaceus	Tremoctopodidae
	Uroteuthis duvauceli	Loliginidae

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