Squid engage in internal fertilization, but rather than using a penis for the transference of sperm cells, the males place a packet of sperm cells, called a spermatophore, into the female’s mantle, or body cavity; however, individual squid species exhibit variations on this general model. Shortly after this sperm transfer takes place, the female excretes fertilized eggs into the water.
Many male squid species possess long, specialized tentacles or arms for transferring spermatophores. In many cases, these tentacles break off once inside the female. Some species engage in elaborate courtship rituals that feature a “mating dance” and stunning visual displays in which the squid change colors rapidly. Females of some species only mate with one male while others are polyandrous and mate with up to three different males at three different times. In some species, the largest males are the most successful breeders while in others the males are not even as large as the females.
Most squid are semelparous, meaning that they only breed during one season before they die. While some species live long lives and are capable of breeding in consecutive seasons, many squid species experience a very high mortality rate. This makes it rare for squid to live long enough to breed twice.