Sperm is the New Superfood: Female Squid Munch Ejaculate For Healthier Eggs

Could eating sperm be good for you? In the case of a certain Australian squid, it is. Biologists have discovered that the female southern bottletail squid eats the sperm of its male counterpart during the course of mating.

The act of eating sperm has never been seen before in a cephalopod, the group of animals that includes squid, octopus, cuttlefish and nautilus. That doesn't mean that other animals don't indulge, though. Species such as carrion flies, picture wing flies, a marine nudibrach and even humans partake in sperm swallowing, according to Discovery News.

In the case of the squid, though, there's a reason for this behavior. A female squid ingests the sperm in order to use the nutrients to aid in the growth of her unfertilized eggs. The findings have enormous implications for how males invest in mating opportunities, especially since smaller females tend to ingest more of the sperm than larger females.

Located off of the coast of South Australia in shallow coastal waters, the southern bottletail squid can be found in sandy habitats near seagrass beds. During the day, it remains buried in the sand. Yet during the night, it emerges to feed on small crustaceans. Mating can occur at an early age, and the eggs are usually attached to the base of seaweeds or seagrass blades.

"These squid live for just a year and have only a single breeding season before they die, so it's not surprising that the males can be highly strategic when evaluating potential mates," said Benjamin Wegener, one of the researchers, in a news release. "The findings suggest that males who copulate with smaller females could pay a higher price for their ejaculate expenditure."

In this case, it seems that choosing a bigger female pays off. During the course of mating, females store sperm from males in an external pouch below their mouths. The male actually passes sperm packages into this pouch where they're stored for later egg fertilization. Yet while some of these packages are stored, others are consumed in order to create the eggs in the first place.

"A male's sperm packages, called spermatophores, take time to produce and he must pass several to the female if he hopes to fertilize her eggs," said Wegener in a news release. "If she is using the nutrients received from ejaculate consumption to develop her unfertilized eggs, he may even be helping the next male that mates with her."

In fact, there's no guarantee that the female will produce eggs at all. The sperm storage only lasts about three weeks in the species. If the female doesn't lay eggs within the timeframe, she'll still gain the nutrients from males through spermatophore consumption. This means that potentially, females could be using male ejaculate as a food source.

"It also raises more questions yet to be explored--are females using males as a food source or as a means to assess the quality of her partners? Are males even capable of using this feeding behavior to manipulate female reproduction? Hopefully future discoveries will uncover the answers," said Wegener.

The findings are published in the journal Biology Letters.