Winning sperm a glowing success
Competitions can be found everywhere in nature. Even the tiniest cells often
need to fight, play hide and seek or run marathons, where winning can mean the
difference between life and death. Most animals’ lives even begin with a race
between competing cells, where the winner is literally awarded with the
opportunity of a lifetime.
Every single sperm cell produced by a male animal holds a random selection of
his genes, resulting in a multitude of cells containing different combinations
of DNA. Some will have groups of genes that will help the animal survive in its
environment, while others won’t work as well. A race is a good way to make sure
only functional sperm have a chance at fertilising the egg at the end and
creating a new life.
Studying this competition in nature, however, can be rather confusing when sperm
from more than one male are in the running. Identifying which cells belong to
which male as they sprint through reproductive tract of a female fruit fly has
now been made a lot easier since a team of biologists in the United States
managed to make them glow different colours.
By adding a gene that makes the heads of the sperm glow red or green under
ultraviolet light, the researchers were able to observe how sperm from two
different male Drosophila fruit flies behaved as they competed.
According to the biologists, the sperm have demonstrated rather complex
behaviours as they wriggle their way towards the egg. By matching particular
strategies with the eventual winner, such as producing chemicals that harm other
sperm cells, it’s possible to work out how some males have developed superior
reproductive techniques.
Occasionally, competition is the last thing a mother-to-be desires. Leafcutter
queen ants can live for twenty years, producing fertilised eggs with a large
amount of sperm they’ve stored away. While male ants are eagre to produce as
many offspring as possible, Danish researchers have found that the queen isn’t
too keen on losing precious sperm cells in a competition. Rather, she
neutralises the chemicals the males produce to harm each other’s cells as they
race, allowing her to fertilise more of her ova and make more ants during her
lifetime.
