A giant corpse recently delivered big news to a team of marine scientists, as the body of a female Architeuthis dux washed ashore with evidence of having only mated with a single individual. The discovery was a surprise to researchers who had long assumed these animals would take every mating opportunity they could to ensure reproductive success among such a solitary species.
Architeuthis, known to some as the “Kraken”, is the largest squid species on Earth and a glimmering example of deep-sea gigantism. It can be up to 13 meters (43 feet) in length for females, 10 meters (33 feet) for males, and is thought to swim at depths of around 300–1,000 meters (980–3,280 feet), though data on this is incomplete owing to their elusive nature. If you're struggling to imagine the size, there's a great shot of one here.
Swimming around in the murky depths is far from the ideal dating setup, and as solitary animals, it was assumed that they would take full advantage of any and all mating opportunities in order to bolster their chances of passing on their DNA. You can track a female’s dating history by looking at the contents of sperm packets embedded in her body, so if this assumption of an opportunistic sex life was true you would expect to find sperm packets from several males.
However, the body of a female Architeuthis dux which recently washed up in Japan told a different story. Containing five separate sperm packets, genetic analyses revealed that each belonged to a single male. It seemed that despite having reached maturity, the female had copulated with just one individual in her lifetime.
"We were almost confident that they are promiscuous," said Noritaka Hirohashi, a biologist at Shimane University in Japan, to Live Science. "We just wanted to know how many males are involved in copulation. So, this is totally unexpected."
That marine scientists don’t fare so well under the crushing pressure of the deep ocean means our understanding of these animals is limited, though a paper published earlier this year detailed the secret recipe to catching these ocean giants on camera with the help of robotic jellyfish.
This incomplete knowledge means that although we understand that the male delivers sperm to the female in these packets, we still have no idea how the sperm eventually meets the eggs. It could be that she holds onto it for a rainy day that’s ripe for some fertilization, or that the sperm moves along receptacles in her skin to reach the eggs.
Now, while nobody’s here to kink-shame squid (whatever arrangement suits them best, have at it), the sperm packets of male squid are really quite something. On several occasions, bold chefs who were apparently short on time have found their mouths and tongues being inseminated by the sperm packets of parboiled squid. The insemination process of a male is autonomous, meaning when the opportunity strikes, the penis produces the sperm which is forcefully shunted into a partner by a muscular arm, be that partner a female squid or human mouth.
Anyway, who’s for calamari?