Evidence for direct use of terminal organ for spermatophore transfer in giant squid, Architeuthis dux

During mating, males of most cephalopods use a modified arm, known as a hectocotylus, to transfer spermatophores into the female. However, a long-standing enigma has been whether some deep-sea squids use a terminal organ (TO), similar to a penis, for direct spermatophore transfer, as suggested by anatomical observations. Here, we present evidence supporting this hypothesis in the giant squid, Architeuthis dux . Two male squids in the moribund condition were discovered in shallow water, with their TOs passing through their own funnels and being able of active movement, a behavior previously observed in Pholidoteuthis adami in deep water.