The southern bottletail squid is a discreet marine cephalopod that buries itself during the day in sand, and then emerges at night to feed on small shellfish. During mating periods, their behavior becomes even more intriguing, as males court young females who store their sperm.

Australian researchers have now found that the squid's sperm may provide nutritional aid during mating after females consume the ejaculate to develop unfertilized eggs and possibly boost offspring production.

"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 Benjamin Wegener, lead author and researcher at Monash University's School of Biological Sciences in Australia. "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."

The researchers looked at the mating behaviors of 51 sexually mature squids from Port Phillip Bay, located in southern Victoria, Australia. They fed these squids with radioactive crustaceans so that when they began producing sperm, the ejaculates could be traced, specifically if they were ingested at different levels in females.

The team found that males assisted in increasing fertilization by replacing a rival's sperm with their own. But more importantly, the smaller females tended to consume more sperm than larger females, providing insight into how these squids choose mates, particularly the larger ones.

"The findings suggest that males who copulate with smaller females could pay a higher price for their ejaculate expenditure," Wegener said. "By targeting those larger females less likely to consume their spermatophores, male southern bottletail squid attempt to maximize their chances for successful egg fertilization."

The researchers said that the males lay their sperm for females close to fertility period to not only grow the unfertilized eggs, but also because rival males could actually swoop in and steal their females once the eggs are mature enough to produce offspring.

"If a male produces an ejaculate that isn't able to successfully compete in the egg fertilization race, he is essentially an evolutionary dead end," Wegener added.

The squid, which only grows up to four centimeters long, is found in sandy environments close to seagrass beds in Southern Australia. It is also found in marine fisheries of the eastern Indian Ocean.

"Our research has shown how sexual selection, common to all sexually reproducing species, is capable of shaping a species' reproductive strategies in some of the most unexpected ways," Wegener said. "But 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."


Wegener BJ, Stuart-Fox DM, Norman MD, et al. Spermatophore consumption in a cephalopod. Biology Letters. 2013.

Wegener BJ, Stuart-Fox DM, Norman MD, et al. Strategic male mate choice minimizes ejaculate consumption. Behavioral Ecology. 2013.