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Hatching Coastal Taipans. Photo credit: Luke Allen |
A
snake curator studying in Darwin may have solved a puzzle that has confused
experts for years.
Just
how can some female snakes store sperm after mating, sometimes for months,
before using it to fertilize their eggs?
The
rare phenomenon has been recorded in snakes in different parts of the world.
Now
Luke Allen, who curates a venom laboratory in South Australia, has used his
captive snakes to find out how.
Studying
the coastal taipan, Australia's longest venomous snake and one of the deadliest
snakes in the world, he learned that the snakes can store sperm for up to six
months after mating.
To
do so he believes they use special cells in their bodies that secrete sugars
and proteins to keep the sperm alive.
The
sperm are kept in small pockets along a spongy tube that leads to the snakes'
ovaries.
"It
had been known that they had this ability but we didn't know how or why,"
said Mr Allen, who studies Environmental Science at Charles Darwin University.
His
six-year study also hinted at why snakes store sperm for such long periods.
The
answer is bad news for people who dislike the creatures, which live in northern
Australia and parts of Papua New Guinea.
"We
found it was related to the food available," he said.
By
altering the number of rats he gave them to eat, Mr Allen learned that when
conditions were good the snakes could give birth to three clutches of eggs
after a single mating.
Storing
the sperm from a single coupling meant they could produce three times as many
eggs than would have been possible if they did not have the ability.
If
times were tough and the snakes were not fed as much they used the sperm all at
once.
Mr
Allen said while conditions for coastal taipans were fairly stable, the snake
was a close relative of the inland taipan, which sometimes had to go for years
between rainy periods in Central Australia.
It
is this variability which may have given rise to the unusual ability.
But
the coastal taipan is not the only snake in the world to be able to delay the fertilization
of its offspring.
A
rattlesnake in the USA kept alone in captivity for five years unexpectedly gave
birth in 2010 to 19 neonates, according to a report.
Other
snakes can have so-called "virgin births" where they give birth to
healthy young without the need to mate.