'Fossil eel' squirms into the record books

(AFP) Google News 16 Aug 11;

PARIS — A new species of eel found in the gloom of an undersea cave is a "living fossil" astonishingly similar to the first eels that swam some 200 million years ago, biologists reported on Wednesday.

The strange find was made last year in a 35-metre- (113-feet) deep fringing-reef cave off an island in the Western Pacific state of Palau, they said in the British journal Proceedings of the Royal Society B.

The small brown fish has very few of the anatomical characteristics of modern eels, a vast range whose 819 species are grouped into 19 families.

In contrast, it has many hallmarks of primitive eels which lived in the early Mesozoic era, back when dinosaurs ruled the Earth.

The similarities include a disproportionately large head, a short compressed body, collar-like openings on the gills, rays on the caudal fin and a jawbone tip called a premaxilla.

The find is so exceptional that the eel not only has been honoured as a separate species, Protoanguilla palau. It also occupies the only niche in a freshly-created taxonomic family, Protoanguillidae.

The name comes from the Greek word "protos," meaning first, and the Latin word for eel, anguilla.

The discovery was made in March last year by a team led by Masaki Miya of the Natural History Museum and Institute in Chiba, Japan.

Using hand nets and lamps, they collected eight specimens, about six to nine centimetres (three to four inches) long, and carried out DNA tests to assess the fish's place in the eel genetic history.

So far, P. palau has only been found in this one location, but it may well have a far wider distribution, according to the study.

The term "living fossil" was coined by Charles Darwin in his book On the Origin of Species.

It is used to describe species that have survived for millions of years, exploiting niches that are so stable that there is little pressure on them to evolve.

New Pacific eel is a 'living fossil', scientists say
BBC News 17 Aug 11;

A newly discovered eel that inhabits an undersea cave in the Pacific Ocean has been dubbed a "living fossil" because of its primitive features.

It is so distinct, scientists created a new taxonomic family to describe its relationship to other eels.

The US-Palauan-Japanese team say the eel's features suggest it has a long and independent evolutionary history stretching back 200m years.

Details appear in the journal Proceedings of the Royal Society B.

The animal used as the basis for the new study was an 18cm-long female, collected by one of the researchers during a dive at a 35m-deep cave in the Republic of Palau.

But the scientists also mention other examples of the new eel species in their research paper.

At first there was much discussion among the researchers about the animal's affinities. But genetic analysis confirmed that the fish was a "true" eel - albeit a primitive one.

"In some features it is more primitive than recent eels, and in others, even more primitive than the oldest known fossil eels, suggesting that it represents a 'living fossil' without a known fossil record," write the scientists.

In order to classify the new animal, the researchers had to create a new family, genus and species, bestowing on the animal the latin name Protoanguilla palau.

The team - including Masaki Miya from Chiba's Natural History Museum in Japan, Jiro Sakaue from the Southern Marine Laboratory in Palau and G David Johnson from the Smithsonian Institute in Washington DC - drew up a family tree of different eels, showing the relationships between them.

This allowed them to estimate when the ancestors of P. palau split away from other types of eel.

Their results suggest this new family has been evolving independently for the last 200m years, placing their origins in the early Mesozoic era, when dinosaurs were beginning their domination of the planet.

The researchers say the Protoanguilla lineage must have once been more widely distributed, because the undersea ridge where its cave home is located is between 60 and 70 million years old.

Most Primitive Living Eel Discovered: Creating a New Species, Genus and Family of Animal
ScienceDaily 17 Aug 11;

Scientists at the Smithsonian and partnering organizations have discovered a remarkably primitive eel in a fringing reef off the coast of the Republic of Palau. This fish exhibits many primitive anatomical features unknown in the other 19 families and more than 800 species of living eels, resulting in its classification as a new species belonging to a new genus and family.

The team's research is published online in the Proceedings of the Royal Society B, Aug. 17.

Many of the physical features of this new genus and species of eel, Protoanguilla palau, reflect its relationship to the 19 families of Anguiliformes (true eels) currently living. Other, more primitive physical traits, such as a second upper jaw bone (premaxilla) and fewer than 90 vertebrae, have only been found in fossil forms from the Cretaceous period (140 million to 65 million years ago). Still other traits, such as a full set of bony toothed "rakers," in the gill arches are a common feature in most bony fishes, but lacking in both fossil and living eels. The team's analyses of total mitochondrial DNA indicate that P. palau represents an ancient, independent lineage with an evolutionary history comparable to that of the entire order of living and fossil eel species.

"The equivalent of this primitive eel, in fishes, has perhaps not been seen since the discovery of the coelacanth in the late 1930s," said Dave Johnson, ichthyologist at the Smithsonian's National Museum of Natural History and lead author of the team's research. "We believe that such a long, independent evolutionary history, dating back to the early Mesozoic (about 200 million years ago), retention of several primitive anatomical features and apparently restricted distribution, warrant its recognition as a living fossil."

Anguilliformes, a distinct group of bony fishes, first appeared in the fossil record about 100 million years ago. They eventually lost their pelvic fins, and their dorsal, anal and caudal fins became continuous. Living eels are very diverse and can be found in a large variety of habitats -- from shallow coastal waters to the deep open ocean.

"The discovery of this extraordinary and beautiful new species of eel underscores how much more there is to learn about our planet," Johnson said. "Furthermore, it brings home the critical importance of future conservation efforts -- currently this species is known from only 10 specimens collected from a single cave in Palau."

Journal Reference:

G. D. Johnson, H. Ida, J. Sakaue, T. Sado, T. Asahida, M. Miya. A 'living fossil' eel (Anguilliformes: Protoanguillidae, fam. nov.) from an undersea cave in Palau. Proceedings of the Royal Society B: Biological Sciences, 2011; DOI: 10.1098/rspb.2011.1289