hectocotylus

From New Latin, corresponding to hecto- +‎ Ancient Greek κότυλος (kótulos, “small cup”).

hectocotylus (plural hectocotyli)

1. (zoology) A modified arm of any of several male cephalopods that functions as a reproductive organ by transferring sperm to the mantle of the female. [from 19th c.]
   • 2017, Danna Staaf, Squid Empire, ForeEdge, →ISBN, page 170:

     When not in use, the male's hectocotylus hides in a pouch, leaving him to go about his business with only seven arms.

   • 2018 January 24, Elsa Panciroli, The Guardian:

     The hectocotylus, like many other genitals, is made of soft tissues which are unlikely to be fossilised.

• hectocotylize, hectocotylise
  • hectocotylized, hectocotylised