What role does the hectocotylus play in cephalopod mating?

The hectocotylus is a specialized arm in male cephalopods that plays a critical role in reproduction by facilitating the transfer of spermatophores to the female.12

During courtship, the male uses this modified appendage to remove spermatophores from his own storage organs and deposit them either within the female’s mantle cavity or on a pad near her mouth. The structure of the hectocotylus varies by species; for example, it may feature a deep groove for guiding spermatophores or a spoonlike terminal organ.2

In some species, such as the argonaut and certain octopods, the hectocotylus is highly modified and undergoes autotomy, meaning it is self-amputated and left inside the female’s mantle cavity to ensure fertilization. In other cephalopods, such as the common octopus, the male may insert the arm into the female's mantle cavity for an extended period to complete the transfer.12