Southern Bottletail Squid. (Photo Credit: Julian Finn/Source: Museum Victoria)
Female squid ingest mates' sperm, an unprecedented sexual behaviour
Thursday, June 06, 2013, 03:30 (GMT + 9)
Recent studies have discovered additional ways in which the male sexual behaviour of the southern bottletail squid (Sepiadarium austrinum) around the Spencer Gulf in Southern Australia produces the maximum amount of offspring.
It seems that the female squid ingest the ejaculates of their mates after these shoot it into the females’ buccal cavity, a trait unique to any species of cephalopod, and uses those nutrients to help her unfertilized eggs grow. This then influences how males approach mating, especially because smaller females were seen to ingest more of the male's ejaculate than larger ones.
The findings were published in the journals Biology Letters and Behavioral Ecology.
PhD student Benjamin Wegener at Monash University's School of Biological Sciences, leader of the study, said this could explain why males preferred to mate with larger females in an attempt to minimise ejaculate consumption and better their chances for egg fertilization.
"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," Wegener said. "The findings suggest that males who copulate with smaller females could pay a higher price for their ejaculate expenditure."
Both sexes start mating early on, and females store males’ sperm in an external pouch below their mouth for later egg fertilization.
"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. 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," Wegener said.
These squid attempt to maximise their chances for egg fertilization by targeting larger females who are less likely to eat their spermatophores, he continued.
Further, the males were more likely to successfully transfer spermatophores to females already carrying eggs.
The sperm will degrade after only about three weeks and, if females do not lay eggs within this time, they still gain the nutrients, ABC reports.
Wegener commented that this research has shown how sexual selection can shape a species' reproductive strategies in very unexpected ways.
"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 behaviour to manipulate female reproduction? Hopefully future discoveries will uncover the answers," Wegener added.
By Natalia Real