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Ancient Scottish fish 'first to have sex'
Topic Started: 20 Oct 2014, 12:00 AM (25 Views)
skibboy
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19 October 2014

Ancient Scottish fish 'first to have sex'

By Rebecca Morelle
Science Correspondent, BBC News

Posted Image
Artist's impression: The researchers believe the fish had to be side-by-side to copulate

Scientists believe they have discovered the origin of copulation.

An international team of researchers says a fish called Microbrachius dicki is the first-known animal to stop reproducing by spawning and instead mate by having sex.

The primitive bony fish, which was about 8cm long, lived in ancient lakes about 385 million years ago in what is now Scotland.

The research is published in the journal Nature.

Lead author Prof John Long, from Flinders University in Australia, said: "We have defined the very point in evolution where the origin of internal fertilisation in all animals began.

"That is a really big step."

Prof Long added that the discovery was made as he was looking through a box of ancient fish fossils.

He noticed that one of the M. dicki specimens had an odd L-shaped appendage.

Further investigation revealed that this was the male fish's genitals.

"The male has large bony claspers. These are the grooves that they use to transfer sperm into the female," explained Prof Long.

Posted Image
Microbrachius dicki fossils are common - but nobody noticed the sexual organs until now

The female fish, on the other hand, had a small bony structure at their rear that locked the male organ into place.

Constrained by their anatomy, the fish probably had to mate side by side.

"They couldn't have done it in a 'missionary position'," said Prof Long. "The very first act of copulation was done sideways, square-dance style."

He added that the fish were able to stay in position with the help of their small arm-like fins.

"The little arms are very useful to link the male and female together, so the male can get this large L-shaped sexual organ into position to dock with the female's genital plates, which are very rough like cheese graters.

"They act like Velcro, locking the male organ into position to transfer sperm."

Posted Image
Copulation using this method did not stay around for long - fish reverted to spawning

Surprisingly, the researchers think this first attempt to reproduce internally was not around for long.

As fish evolved, they reverted back to spawning.

It took another few million years for copulation to make a come-back, reappearing in ancestors of sharks and rays.

Commenting on the research, Dr Matt Friedman, from the University of Oxford, UK, said: "The placoderm group (which includes Microbrachius dicki) is a well known group - the fossils are pretty common, and it's not as if this one was found in some far-off, exotic part of the world. It was found in Scotland.

"It is very remarkable that we haven't noticed this before."

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skibboy
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19 October 2014

Sex? It all started 385 million years ago

AFP

Posted Image
Dr. John Long, Head of Sciences at Museum Victoria, inspects a model of a placoderm fish in Melbourne, Australia, on May 28, 2008

It may not have been love as we know it, but around 385 million years ago, our very distant ancestors -- armoured fish called placoderms -- developed the art of intercourse.

So suggest a team of evolutionary scientists who point to the fossil of a placoderm species blessed with the name of Microbrachius dicki.

Measuring about eight centimetres (four inches) in length, M. dicki lived in habitats in modern-day Scotland -- where the first specimen was found in 1888 -- and in Estonia and China.

Placoderms have previously been found to be the most primitive jawed animal -- the earliest known vertebrate forerunner of humans.

But they now have an even more honoured place in the book of life.

Microbrachius is the first known species to copulate in order to carry out internal fertilisation, according to a paper published on Sunday in the journal Nature.

Male fish had bony, L-shaped genital limbs called claspers which transferred sperm into the female, a more effective way of reproduction compared to spawning in the water, the study says.

The females, for their part, developed small, paired bones with which they locked the male organs in place in order to copulate.

"'Microbrachius' means little arms, but scientists have been baffled for centuries by what these bony paired arms were actually there for," said John Long, a professor of palaeontology at Flinders University in Adelaide, Australia.

"We've solved this great mystery because they were there for mating, so that the male could position his claspers into the female genital area."

Until now, it was thought internal fertilisation occurred much later in the evolutionary tale of vertebrates.

With thick, bony plates covering the head and trunk, placoderms ruled the world's oceans, rivers and lakes for around 70 million years.

They were then were wiped out around 360 million years ago in a mysterious mass extinction.

For decades, they were deemed by many palaeontologists to be a curiosity -- an evolutionary branch that failed.

But work by Long and others found them to be far more important.

The critters handed on features such as jaws, teeth and paired limbs that are seen today in reptiles, birds and mammals, including humans.

If the new study is right, the "claspers," over hundreds of millions of years, evolved into the penis.

Microbrachius' copulatory skill was uncovered last year when Long stumbled across a fossil in a collection at the University of Technology in Tallinn, Estonia.

Males and females probably had sex side by side, with their bony jointed genitals locked together, according to the new investigation.

"This enabled the males to maneuvre their genital organs into the right position for mating," Long said.

The position looked, well, rather weird, he admitted.

"With their arms interlocked, these fish looked more like they are square-dancing the do-se-do rather than mating."

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