MASTERING octopuses’ sex lives is the fascinating subject of a study by University of WA Ocean’s Institute-backed James Cook University researcher Peter Morse this summer.
“We want to know just how the females are choosing some males’ sperm over others, because there are often many fathers in any egg clutch,” Mr Morse (28) said.
Last summer, his traps for the cephalopods along the WA coast, including Cottesloe and South Fremantle, contributed to results published in the science journal Behaviour last month.
The venomous male southern blue-ringed octopus being studied is allocated about 50 sperm during its seven-month life.
Females store different males’ sperm in a gland behind their heads, before potentially deciding which to use to fertilise precious eggs, then they dig a burrow or hide to protect their young.
The mothers eventually die after protecting the eggs for two months, while the males die when they have exhausted their sperm.
“We also would like to know how the males seem to be aware of how much sperm the females are holding, and because they have a limited amount of sperm in a lifetime they seem to be regulating the amount they are using,” Mr Morse said.
His previous studies indicated males appear to be able to gauge just how much sperm from their competitors is being held by the females and males change the amount of sperm they leave with a female, while ensuring they have enough left for mating with other females.
“They appear to strategically allocate their limited sperm,” Mr Morse said.
Last month, he started weekly collections from about 200 octopus traps 50m-100m offshore from the former South Fremantle power station, near to where he trapped more than 110 animals in Cockburn Sound a year ago.
”What we’re doing now is verifying the behaviour indicated by our previous research that showed males mate to maximise retention of a limited amount of sperm,” Mr Morse said.