Scientists Find Lamprey A 'Living Fossil': 360 Million-year-old Fish Hasn't Evolved Much

Science Daily.com ^ | October 26, 2006 | University of Chicago Medical Center

[aculeus]

Scientists from the University of Witwatersrand in Johannesburg, South Africa, and the University of Chicago have uncovered a remarkably well-preserved fossil lamprey from the Devonian period that reveals today's lampreys as "living fossils" since they have remained largely unaltered for 360 million years.

Scientists from the University of Witwatersrand in Johannesburg, South Africa, and the University of Chicago have uncovered a remarkably well-preserved fossil lamprey from the Devonian period that reveals today's lampreys as "living fossils" since they have remained largely unaltered for 360 million years. The scientists describe the new find in the article, "A lamprey from the Devonian of South Africa," to be published in the Oct. 26, 2006, issue of Nature. (Image courtesy of University of Chicago Medical Center) Chicago's Michael Coates, PhD, joined Witwatersrand's Bruce Rubidge, PhD, and graduate student and lead author Rob Gess to describe the new find in the article, "A lamprey from the Devonian of South Africa" to be published in the Oct. 26, 2006, issue of Nature.

"Apart from being the oldest fossil lamprey yet discovered, this fossil shows that lampreys have been parasitic for at least 360 million years," said Rubidge, director of the Bernard Price Institute for Palaeontological Research.

Lampreys are long, eel-like parasites that attach themselves to and feed on other fish. Of the 46,000 known species of vertebrates, lampreys and hagfish are the only surviving jawless vertebrates. Lampreys are the most "primitive" of the vertebrates, meaning that they are the least changed from the first vertebrates. Besides lacking jaws, lampreys have no paired pectoral and pelvic fins, and no scales.

"This fossil changes how we look at lampreys today," said Coates, associate professor of organismal biology and anatomy. "They're very ancient, very primitive animals, yet with highly specialized feeding habits."

It reveals that the anatomical evolution of lampreys is more conservative than scientists thought, Coates added. Although they've gotten slightly longer, they specialized early and successfully and thus appeared to have stayed much the same for the past 360 million years.

"This discovery is a monument to the dedication and passion of [Gess], who has spent many months patiently excavating and unearthing the elusive secrets from the prehistoric past," Rubidge said.

Gess found the new specimen, Priscomyzon riniensis, 18 months ago in an ancient estuary in Grahamstown, South Africa. Preserved showing the underside, the fossil measures less than 2 inches long and reveals a set of 14 teeth surrounding the mouth that is proportionately larger than its descendents today.

"The most striking feature of Priscomyzon is its large oral disc, edged with a soft outer lip, supported by an annular cartilage, and surrounding a circular mouth," the authors wrote. "This is the first clear evidence of a Palaeozoic lamprey with an oral disc."

According to the scientists, this find greatly adds to what was a severely limited lamprey fossil record and, for the first time, places the origin of modern lamprey morphology deep within the Palaeozoic period. It adds essential new detail to the emerging and changing picture of early vertebrate evolution.

Until now, the lamprey fossil record included only those that show a side view but reveal little of the gill basket and feeding apparatus. However, earlier this year, Nature reported on a freshwater lamprey fossil found in the Jehol biota of China (Inner Mongolia) from the Early Cretaceous period (about 125 million years ago).

The newly discovered South African fossil shows that these anatomically specialized fish are "holdovers" from ancient marine ecosystems, Coates said. Obviously exceptional survivors, these animals predate the advent of modern fish and have survived at least four major extinction events.

"There are few representatives of these early branches in vertebrate evolution that are still around today," Coates said, which is why so much scientific attention has been paid to lampreys. Although highly specialized in their own right, these primitive animals are used as surrogate ancestors for comparative research on living jawed vertebrates.

"It gives us a calibration point," Coates said. "We study lampreys because, in many respects, they're so primitive. They never had jaws, they never had [true] teeth, they never had fins, they never had limbs. Lampreys provide a glimpse of conditions early in vertebrate evolutionary history."

Because lampreys do not have bone or any substantial cartilage, they are extremely rare as fossils. This fossil not only reveals a nearly complete soft tissue impression, but it also pushes back their fossil record another 35 million years.

"These are pretty insubstantial animals," Coates said. "Lacking a boney skeleton, they rot down, leaving no hard parts, like a skull or ribs. So if a fossil site is discovered that yields impressions of the delicate remains of these animals, then this site needs to be explored thoroughly for other examples of exceptional preservation."

The scientists will continue to sort through much of the indeterminate material that is emerging from the ongoing dig.

Nearly 50 species of lampreys are found today in temperate rivers and coastal seas. Some species live in fresh water for their entire lives, but most are anadromous, hatching in fresh water, migrating to the ocean to grow and mature, and migrating back to fresh water to spawn and reproduce.

When adult lampreys return to fresh water, they stop feeding during winter and spawn the following spring. Eggs hatch after approximately three weeks and become blind larvae, called ammocoetes. After four to seven years, the ammocoetes metamorphose into juvenile lampreys called macropthalmia, which migrate out to the ocean and become parasitic adult lampreys, living just a year or two and growing up to 2 feet long.

Abundant in the Northeast United States, lampreys have a sucker-like mouth with a ring of cartilage that supports the rim of the mouth. It fastens on to a living fish with its teeth, rasps at the host's soft tissues with its piston-like tongue, produces strands of mucus to trap the food and feeds on the body fluids. A fish attacked by lampreys may be severely injured or even killed.

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[muir_redwoods]

P"Yes, but since the world was created 5,000 years ago, you would not expect that it's evolved much."

Actuaally 6004 years just last Tuesday at 9:00 AM

Or so I'm told...:)

[Boxen]

Do not click here if you have a mortal fear of lampreys.

[muir_redwoods]

"Most people would have seen that my thoughts were very clear."

Uhhh, no

[mutley]

"Only a few of an organisms genes specify its shape. Most of the genes control the detailed composition of proteins. There could have been wholesale changes at the cellular level, but you'd never know it from the fossil record."

I don't disagree with that. I seem to tread a road less traveled in this type of thread. To me, there are aspects of the TOE that are undeniable if being intellectually honest with one's self, but there are other aspects, that I think are indeed suspicious.

"The only really surprising result from this discovery is that an ecological niche has remained so stable for 360,000,000 years."

That is shocking to me. And I have to try and surmise, that there is something wrong with this picture.

[taxesareforever]

Then you must not be included in "most".

[muir_redwoods]

You failed to explain the logical leap you made from a lamprey, acted on by almost no outside pressure to adapt and evolve, to a human, probably the species subject to the most stresses and outside forces to adapt and evolve.

[xhrist]

we must continue to refine this theory as new data emerges.

yea..never admit its a hypothesis..

"A hypothesis is a suggested explanation of a phenomenon or reasoned proposal suggesting a possible correlation between multiple phenomena. " A theory is a proposed description, explanation, or model of the manner of interaction of a set of natural phenomena, capable of predicting future occurrences or observations of the same kind, and capable of being tested through experiment or otherwise falsified through empirical observation"

[mutley]

"almost no outside pressure to adapt and evolve"

THAT...is one HUGE assumption! And spanning 360,000,000 years! Am I to just take your word on that? LOL

[Stultis]

I thought all vertebrates by definition had back bones.

No. Not necessarily bones. They all have a vertebral column, which is not necessarily (and isn't) bony in the most primitive vertebrates.

The largest subgroup within the vertebrates is the craniata, which are animals with a skull. The lamprey is the most primitive of the craniates, with the least developed (and cartiliginous rather than bony) vetrebral column. The only more primitive vertebrate is the hagfish, which (IIRC) is the only living vertebrate that is NOT also a member of craniata. It has cartiliginous plates in it's head, like the lamprey, but unlike the lamprey it lacks a true braincase.

Back to the vertebral column, here's a diagram and discussion I found at The Tree of Life:

Characteristics

The Vertebrata have all the characteristics of the Craniata but share, in addition, a number of unique characteristics which do not occur in hagfishes (Hyperotreti). These characteristics are:

• Metamerically arranged endoskeletal elements flanking the spinal cord. There are primitively two pairs of such elements in each metamere and on each side: the interdorsals and basidorsals. In the gnathostomes, there are two additional pairs ventrally to the notochord: the interventrals and basiventrals. These elements are called arcualia and can fuse to a notochordal calcification, the centrum. The ensemble of the arcualia + centrum is the vertebra, and the ensemble of the vertebrae is the vertebral column.

  ---

  

  The vertebrates are characterized by a vertebral column; that is, a variable number of endoskeletal elements aligned along the notochord (green) and flanking the spinal cord (yellow). In lampreys (top), the vertebral elements are only the basidorsal (red) and the interdorsals (blue). In the gnathostomes, there are in addition ventral elements, the basiventrals (purple) and interventrals (orange), and the notochord may calcify into centra (pink). (After Janvier 1996).

[muir_redwoods]

"Am I to just take your word on that? LOL"

Yes.

It's a well adapted, parasite that feeds on blood. As long as there are other creatures with blood (and no hands with which to remove it), the lamprey will eat. Any population of lampreys that were acted on by significant forces may well have evolved into something else but the basic design of the lamprey and it's niche is well protected. So long as creatures with blood live in the sea.

[muawiyah]

In contrast to the pitifully few lampray species, mosquitos, also blood suckers, have proliferated as few other animals ever have.

They are everywhere!

Admit it, the lampray is the perfect animal ~ untouched by the forces of Natural Selection ~ beyond mere statistics.

[mutley]

"So long as creatures with blood live in the sea."

I'm sorry, but you should have said, so long as creatures exist with skin, or scales, or something else, have existed which the lamprey's blood sucking equipment can access, have lived in the sea. Any type of statement like this which proposes to cover 360,000,000 years of evolution, is quite suspicious to me.

[balch3]

exactly, although it's more like 6000.

[taxesareforever]

You failed to explain the logical leap you made from a lamprey, acted on by almost no outside pressure to adapt and evolve, to a human,

Ah, did you read my post correctly? I don't believe in evolution so why would I even suggest that there was a "leap from lamprey to humans"?

[Dimensio]

You failed to explain the logical leap you made from a lamprey, acted on by almost no outside pressure to adapt and evolve, to a human, probably the species subject to the most stresses and outside forces to adapt and evolve.

If I may speculate, I believe that the failure is a direct result of there being absolutely no logical basis for taxesareforever's claim.

[ml1954]

'Genesis = Science Textbook' ping.

[fish hawk]

So the eel hasn't changed in 360 million years but apes turned into men. Boy, evolution sure is fickle. Or else its all bull crap.

[Stultis]

In contrast to the pitifully few lampray species, mosquitos, also blood suckers, have proliferated as few other animals ever have.

It appears by the most common classification schemes there are about 40 species of lamprey distributed among 9 or 10 genera and 3 subfamilies, lampreys themselves collectively constituting a family. This makes lampreys about as diverse as horses (that is including horses, zebras, donkeys, asses, etc). I wouldn't call that "pitifully few" species.

Yes, there are far more species of mosquitoes. But then, as you probably already know, insects in general are far, far, far more diverse in numbers of species than animals, and the distinction would be just about as striking in the case of any comparable analogy between animal and insect.

lampray is the perfect animal ~ untouched by the forces of Natural Selection ~ beyond mere statistics

I'm no expert on the critters, but at least at first blush I don't think I'd call all of the variation in living lamprey species "mere statistics". I think the differences in adaptation between living life-long in fresh water, versus a life cycle transitioning from fresh water to the ocean and back to fresh water, and even among the sea going lampreys some that are merely coastal versus others that appear to range across vast distances, and a range of (adult) feeding habits from pure parasite to pure predator, are at least a little bit "beyond mere statistics".