Posts Tagged ‘Sexual Reproduction’

Fish 380 Million Years Old Found With Unborn Embryo

June 6, 2008

In 2005, Museum Victoria’s expedition to the Gogo fossil sites in north Western Australia, led by Dr John Long, made a swag of spectacular fossil discoveries, including that of a complete fish, Gogonasus, showing unexpected features similar to early land animals.

Now the same team has made a new discovery: a remarkable 380-million-year-old fossil placoderm fish with intact embryo and mineralised umbilical cord.

The discovery, published in Nature, makes the fossil the world’s oldest known vertebrate mother. It also provides the earliest evidence of vertebrate sexual reproduction, wherein the males (which possessed clasping organs similar to modern sharks and rays) internally fertilised females.

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Common Aquatic Animal’s Genome Can Capture Foreign DNA

May 29, 2008

Long viewed as straitlaced spinsters, sexless freshwater invertebrate animals known as bdelloid rotifers may actually be far more promiscuous than anyone had imagined: Scientists at Harvard University have found that the genomes of these common creatures are chock-full of DNA from plants, fungi, bacteria, and animals.

The finding, described May 30 in the journal Science, could take the sex out of sexual reproduction, showing that bdelloid rotifers, all of which are female, can exchange genetic material via other means.

“Our result shows that genes can enter the genomes of bdelloid rotifers in a manner fundamentally different from that which, in other animals, results from the mating of males and females,” says Matthew S. Meselson, Thomas Dudley Cabot Professor of the Natural Sciences in Harvard’s Faculty of Arts and Sciences.

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Rethinking evolution: Sex and complexity came a lot sooner than we thought

March 20, 2008

Two paleontologists studying ancient fossils they excavated in the South Australian outback argue that Earth’s ecosystem has been complex for hundreds of millions of years — at least since around 565 million years ago, which is included in a period in Earth’s history called the Neoproterozoic era.

Until now, the dominant paradigm in the field of paleobiology has been that the earliest multicellular animals were simple, and that strategies organisms use today to survive, reproduce and grow in numbers have arisen over time due to several factors. These factors include evolutionary and ecological pressures that both predators and competition for food and other resources have imposed on the ecosystem.

But in describing the ecology and reproductive strategies of Funisia dorothea, a tubular organism preserved as a fossil, the researchers found that the organism had multiple means of growing and propagating — similar to strategies used by most invertebrate organisms for propagation today.

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