Daily Archives: April 18, 2013

Workers at the National Museum of Kenya show a coelacanth caught by Kenyan fishermen in 2001.

Workers at the National Museum of Kenya show a coelacanth caught by Kenyan fishermen in 2001.

Scientists have unraveled the genome of the coelacanth, a rare and primitive fish once thought to be extinct, shedding light on how closely it's related to the first creatures to emerge from the sea.

The coelacanth, a fish that can reach up to 5 feet long and lives in deep ocean caves, had only been seen in fossils and was thought to have gone extinct some 70 million years ago. That was until 1938, when fishermen from the Comoros islands off the coast of Africa captured one in a net. A second coelacanth species was discovered off the Indonesian island of Sulewesi in 1997.

The coelacanth's genome shows "that the lungfish, and not the coelacanth, is the closest living relative to the tetrapods," according to an abstract of a study published in the journal Nature.

"The lungfish-coelacanth question has gone back and forth over the years; the lungfish answer is not new, but this is a much better, bigger data set so it does tip the balance a bit," researcher John Hutchinson, professor of evolutionary biomechanics from the Royal Veterinary College, told the BBC.

According to National Geographic:

"The most striking feature of this 'living fossil' is its paired lobe fins that extend away from its body like legs and move in an alternating pattern, like a trotting horse. Other unique characteristics include a hinged joint in the skull which allows the fish to widen its mouth for large prey; an oil-filled tube, called a notochord, which serves as a backbone; thick scales common only to extinct fish, and an electrosensory rostral organ in its snout likely used to detect prey."

The analysis of the genome also shows that the coelacanth's genes evolved very slowly, an apparent confirmation of what paleontologists have long believed that the fish has changed little in the past 400 million years.

"If you think about it, this might be correlated to the fact that the coelacanth lives in a rather extreme and stable environment," Professor Kerstin Lindblad-Toh, from the University of Uppsala in Sweden and the Broad Institute of MIT and Harvard, told the BBC.

Read the original here:
Scientists Sequence Genome Of 'Living Fossil' Fish

An international team of researchers join forces to decode the genome of the once-thought-to-be-extinct African coelacanth

Singapore, Apr 18, 2013 - (ACN Newswire) - An enigmatic prehistoric fish has brought scientists at A*STAR's Institute of Molecular and Cell Biology (IMCB) together with researchers from all over the world to crack its genomic code. Findings from the study are providing new insights into the evolutionary history of the African coelacanth (Figure 1)(1) and possible clues as to how aquatic creatures transitioned to life on land.

Coelacanths resemble the fossilised skeletons of their ancestors from more than 300-million years ago (Figure 2). By sequencing its genome and comparing it to genes of other vertebrate species, the researchers have uncovered valuable information on genetic changes that may have helped aquatic animals to transition from water to land, and adapt to life on land. Their findings include many genes and regulatory elements that were gained and genes that were lost when vertebrates came on land. The research findings were published in the 18 April online issue of the prestigious journal, Nature.

The most interesting feature of the coelacanth is its fleshy fins, which resemble the limbs of land animals (Figure 3). The team has found several important regions of the genome used in the formation of limbs, which suggest that land animals (tetrapods) adopted these sequences from coelacanths to help them form limbs. The researchers also found that there are many regulatory changes that influence genes involved in the perception of smell, as creatures that transitioned to land needed new means of detecting chemicals in their environment.

While sequencing the genome of the coelacanth provides some answers, more information on how some vertebrates adapted to land while others remained in the water can be discerned from future research of coelacanth's physiological systems such as the immune system, respiratory system, and reproductive system.

Prof. Byrappa Venkatesh, Research Director IMCB, whose group was involved in the project said, "The coelacanth with its distinctive fleshy fins represents an intermediary phase in the evolution of land animals from aquatic fishes. By comparing the genomes of coelacanth, human and other vertebrates our group has been able to discover gene regulatory elements that played a key role in the development of our limbs and fingers as well as our ability to detect air-borne odorants. Mutations in these elements can potentially lead to genetic diseases."

Prof Hong Wan Jin, Executive Director IMCB, said, "This is the same IMCB group that sequenced the puffer fish genome in 2002 soon after the completion of the human genome and they are truly a pioneer in the field of comparative genomics. I am pleased to note that they are now part of yet another major international collaboration in genomics and are continuing to make significant contributions to our understanding of the structure, function and evolution of the human genome."

Press document (with Figures): http://www.a-star.edu.sg/?TabId=828&articleType=ArticleView&articleId=1803

(1) A deep-sea cave dwelling, five-foot long fish with limb-like fins

Notes for Editor:

Read more from the original source:
A*STAR Scientists Decipher Genome Code of a Living Fossil

17 April 2013 Last updated at 13:54 ET By Rebecca Morelle Science reporter, BBC World Service

The genetic secrets of a "living fossil" have been revealed by scientists.

Researchers sequenced the genome of the coelacanth: a deep-sea fish that closely resembles its ancestors, which lived at least 300 million years ago.

The study found that some of the animal's genes evolved very slowly, giving it its primitive appearance.

The work also shed light on how the fish was related to the first land-based animals.

The coelacanth has four large, fleshy fins, which some scientists believe could have been the predecessors of limbs.

It had been suggested that this fish was closely related to early tetrapods - the first creatures to drag themselves out of the ocean, giving rise to life on land.

But the study, published in the journal Nature, suggested that another fish called the lungfish, which also has four limbs, had more genes in common with land-based animals.

Slow to change

The coelacanth can reach up to 2m-long and is found lurking in caves deep beneath the waves.

See more here:
Genome of 'living fossil' sequenced

Aquamarine Fukushima

An African coelacanth, photographed using a Remotely Operated Vehicle off the coast of Tanga, Tanzania.

By John Roach, Contributing Writer, NBC News

The genome of the coelacanth, an ancient-looking lobed-finned fish, has been sequenced and is already providing insight to the evolutionary changes that allowed the first four-limbed animals, called tetrapods, to crawl out of the water and on to land.

The sequence and preliminary analysis, reported Thursday in the journal Natureby a team spanning 40 research institutions and 12 countries,is a "massive piece of work," Xiaobo Xu, a paleontologist at Kean University who was not involved in the effort, told NBC News in an email.

"The paper really provides rare and valuable genomic data for offering heavy-weight opinions on issues bearing on the fish (to) tetrapod transition," he said.

It also settles a debate that has long raged amongst evolutionary biologists: what fish is the closest relative of tetrapods: the coelacanth or the equally odd-looking lobed-finned lungfish. The winner, according to analysis of the newly-published genome, is the lungfish.

"We think we have definitively shown it now," Jessica Alfldi, a research scientist at the Broad Institute of MIT and Harvard and co-first author of the paper, told NBC News. "They are very close, which is why it took so much data to figure it out."

Slow evolving genes Scientists thought coelacanths went extinct about 70 million years ago, during the Late Cretaceous period. That changed when a fish trawler off the South African coast delivered a fresh-caught coelacanth to a local natural history museum in 1938, proving that the fish are alive and well.

The coelacanths' odd, ancient-looking looks raised eyebrows and earned it the nickname "living fossil" much to the chagrin of evolutionary biologists, noted Alfldi. ("It makes people think there was no evolution," she explained.)

Read more:
Genome of ancient-looking fish gives clues to first limbed landlubbers