A modified arm used by male octopuses and some other cephalopods to transfer sperm to the female.
- ‘In some species, the specialized arm tip may be pinched off and left in the female's mantle cavity: this is known as the hectocotylus arm.’
- ‘The hectocotylus is used to deliver the spermatophores (sperm-filled sacs) to the female during mating.’
- ‘In some cephalopods, the end of the hectocotylus snaps off and remains imbedded in the female.’
Mid 19th century modern Latin, from hecto-‘hundred’ + Greek kotulē ‘hollow thing’, a name given by Cuvier to what he mistakenly took to be a genus of parasitic worms.