Definition of hectocotylus in US English:


nounPlural hectocotyli

  • 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.