A study which pinpoints exactly how sperm wiggle may one day help develop better diagnostic tests for infertility.
Sperm were thought to go into a 'hyperactive' drive just before encountering the egg in order to break through the egg's wall, but researchers now suggest that this kind of swimming behaviour is much more common.
Hyperactive sperm jerk their tails much more strongly and asymmetrically than sperm not swimming in this mode.
'Rather than starting off in one stroke and ending up in another, they're switching back and forwards all the time,' study leader, Dr Stephen Publicover at the University of Birmingham, told the New Scientist.
His team videoed the behaviour of individual sperm over three-minute periods and found repeated and abrupt changes in behaviour in 16 of the 18 sperm cells.
'Such behavioural switching may be adaptive, for instance during ascent of the female tract by "hopping",' wrote the researchers in their abstract.
Indeed, hyperactivated sperm in mice appear to be better at escaping from pockets in the wall of the fallopian tube, according to Professor Susan Suarez at Cornell University in Ithaca, New York.
The study was presented at the Fertility 2019 conference in Birmingham in January.