Fish "missing link" found

[Split Rock]

Wonky-Eyed Fish Link: DNews Nuggets : Discovery News

From the article:

There are about 600 species of flatfish, many of which are caught and eaten by humans. Scientists know why these fish have two eyes on one side of their faces. As free-swimming larvae, these fish have eyes on both sides of their heads. But as adults, they lie on the seafloor. By shifting one eye up and over their body's midline, flatfish avoid pointing one eye down toward the sediment.

But how this arrangement emerged has caused debate among scientists, since no living fishes show any intermediate form. At one point, flatfishes were among the examples some critics used to attack gradual evolution and natural selection that occurs over many generations, in favor of dramatic changes that could occur within a single generation, Friedman said.

"What this fossil does is it provides a clear example of precisely that intermediate morphology," Friedman told LiveScience.

I can't find the article at your link. Is it still there somewhere?

 

[rush1169]

nm

 

[CabVet]

Oh, so you're saying that it doesn't matter why it's eye was is in the wrong place, the fact that it is weighs more heavily in favor of it being a transitional creature than any other possibility, including a birth defect, because of it's relative position in the strata?

Sorry for the dumb questions - I'm still learning.

Not only position in strata, but also other morphological similarities between flatfishes and their ancestors. As you might know, fossils require very specific conditions to form, so are rare, and fish with these genetic defects are also rare. In this case, the fossil not only is in the expected relative position in the strata, but it also belongs to the family of fish that are ancestors of flatfishes. So, the odds of finding a fossil that looks like an ancestor of a flatfish, but with a genetic defect (meaning it is an unique individual, instead of it being part of a large population) at the expected strata are exceedingly small.

It is possible, I guess, but the probability of that happening is insignificantly small.

 

[CaliforniaSun]

Oh, so you're saying that it doesn't matter why it's eye was is in the wrong place, the fact that it is weighs more heavily in favor of it being a transitional creature than any other possibility, including a birth defect, because of it's relative position in the strata?

Sorry for the dumb questions - I'm still learning.

No, we're saying that this particular mutation was selected for, rather than against, for this creatures survival. Obviously those fish who were able to have better vision while living on the sea floor survived predators long enough to pass on these mutations.

 

[Split Rock]

Just a drive-by observation, not to imply my endorsement or non-endorsement of biological evolution, but this made me beg a question (to follow):



Wouldn't it more likely be a defect in the DNA that resulted in a signal for the eye to stop prematurely? Alternatively, wouldn't it be more likely that the signal for the eye to move never properly fired, but as the fish grew, the left eye wasn't 'anchored' and simply ended up where it did?

Oh, so you're saying that it doesn't matter why it's eye was is in the wrong place, the fact that it is weighs more heavily in favor of it being a transitional creature than any other possibility, including a birth defect, because of it's relative position in the strata?

Sorry for the dumb questions - I'm still learning.

I don't think CabVet understood your question. You are asking if it is possible that the specimen's attributes are do to a deformation, and are not a trait of its species... correct? While that is possible it is rather unlikely. That said, a second specimen of the same species (or closely realted one) would answer your question.

 

[CabVet]

I can't find the article at your link. Is it still there somewhere?

Yeah, I just realized the original article is much older, from 2008, so I don't know why all of a sudden the subject is all over the media again. Here is the link to the original article:

http://www.nature.com/nature/journal/v454/n7201/full/nature07108.html

And a press release from 2008:

http://www.uchospitals.edu/news/2008/20080709-flatfish.html

 

[Split Rock]

You guys who believe in missing links ... do you have names for these animals made up ahead of time; or, as I suspect, are they called 'transitional' and named after they're found?

I don't think there are names set aside in advance. They are called "transitional" when the requirements are met.

 

[AV1611VET]

They are called "transitional" when the requirements are met.

But here's what I don't understand:

I thought ... according to you (?) ... we are all transitionals.

Even I am a transition between my father and my son.

So anything found would be a 'transitional' ... would it not?

 

[rush1169]

Not only position in strata, but also other morphological similarities between flatfishes and their ancestors.

I guess what threw me is that the article said it was the only specimen we have. I would've expected at least a two or more individuals morphologically indentical to the one in the article before a transitional declaration could be with confidence. Of course, that makes me wonder if there is a fish that, besides the wonky eyeball, is otherwise indentical to this specimen or does this guy have other differences as well. . .then that makes me wonder if the lazy-eye was a birth defect that may have included other morphological, non-life ending, defects, but then you said that it's not a birth defect, so. . .I dunno. For my satisfaction, and I'm more than willing to accept it as transitional, the article didn't provide enough details to send my questions to shutty-town.

Eh, never mind again, your new posting indicates they have more than one of these guys. No idea why the other article said "only one specimen."

 

[CabVet]

I can't find the article at your link. Is it still there somewhere?

Oh, now I get the reason for why the renewed media interest. There is a new (much more detailed) article that was just published:

Friedman, M. Osteology of †Heteronectes chaneti (Acanthomorpha, Pleuronectiformes), an Eocene stem flatfish, with a discussion of flatfish sister-group relationships. Journal of Vertebrate Paleontology, 2012; (32)4: 735-756.

 

[Split Rock]

But here's what I don't understand:

I thought ... according to you (?) ... we are all transitionals.

Even I am a transition between my father and my son.

So anything found would be a 'transitional' ... would it not?

That depends on what you mean by "transitional." When it comes to the fossil record, "transitionals" are species that have characteristics of two different, but related taxonomic groups.

 

[CabVet]

I guess what threw me is that the article said it was the only specimen we have. I would've expected at least a two or more individuals morphologically indentical to the one in the article before a transitional declaration could be with confidence. Of course, that makes me wonder if there is a fish that, besides the wonky eyeball, is otherwise indentical to this specimen or does this guy have other differences as well. . .then that makes me wonder if the lazy-eye was a birth defect that may have included other morphological, non-life ending, defects, but then you said that it's not a birth defect, so. . .I dunno. For my satisfaction, and I'm more than willing to accept it as transitional, the article didn't provide enough details to send my questions to shutty-town.

I totally understand where you are coming from. And completely agree too. As I mentioned before, the reason for why this is being called a "missing link" that was "found", or a transitional, as opposed to something unique, is a combination of characteristics that include it's position in the strata, it's morphological similarity to the flatfish ancestors and other characters in addition to the position of the eye. Check the link above for the complete article, it might give you some more information.

The thing about evolution though is that it is not based in one single specimen of one species. There are literally hundreds of these transitional fossils, and this is just evidence from the fossil record. There are also several other independent lines of evidence that support evolution.

For example, something that creationists avoid discussing a lot is biogeography (or the geographical distribution of organisms in present and past times) and its relation DNA similarities between organisms. From that we can actually make testable predictions about evolution (and most are realized).

 

[CaliforniaSun]

But here's what I don't understand:

I thought ... according to you (?) ... we are all transitionals.

Even I am a transition between my father and my son.

So anything found would be a 'transitional' ... would it not?

It's not hard to understand.

 

[juvenissun]

we don't "believe" in missing links, we accept that the fossil record is not perfe
FYI, this one was named Heteronectes. Here is a photo:

Flatfish have both eyes on the same side of the head. Their ancestors have one eye on each side. The fossil has one eye on the side and the other on top of the head.

Would you expect someday a fish would be found with one eye located at 45° along the circle of rotation?

 

[CabVet]

Would you expect someday a fish would be found with one eye located at 45° along the circle of rotation?

Not necessarily. As I said, we don't know the genetic basis of this adaptation in detail, so not sure if mutations cause big or small jumps in eye position.

 

[Loudmouth]

Would you expect someday a fish would be found with one eye located at 45° along the circle of rotation?

Let's look at a different morphological change which is common in the Vadoma tribe in Africa. In this case, a mutation produced altered foot morphology (and altered hand morphology in some cases).

This single mutation went from 5 toes to 2 toes for each foot. No transitional from 4 to 3 to 2 occurred. It was straight from 5 to 2. For this reason, we shouldn't expect a perfect millimeter by millimeter change for all morphological features.

 

[good brother]

The OP begins with the assumption that the fish's anatomy evolved to fit it's hunting technique when a more apt question concerning this type of fish would be "Did the flatfish's eyes gravitate to one side of the skull to accomodate it's hunting technique or did it's hunting technique come about because of a deformation from other fish with eyes on both sides of their skulls?" A "chicken or egg" kind of question.

In Christ, GB

 

[Split Rock]

The OP begins with the assumption that the fish's anatomy evolved to fit it's hunting technique when a more apt question concerning this type of fish would be "Did the flatfish's eyes gravitate to one side of the skull to accomodate it's hunting technique or did it's hunting technique come about because of a deformation from other fish with eyes on both sides of their skulls?" A "chicken or egg" kind of question.

In Christ, GB

Your question actually makes little sense. The trait did not evolve for any purpose. If a new trait that arrives via mutation or assortive mating is adaptive, then it will increase in a population until it becomes the norm.

 

[Loudmouth]

The OP begins with the assumption that the fish's anatomy evolved to fit it's hunting technique when a more apt question concerning this type of fish would be "Did the flatfish's eyes gravitate to one side of the skull to accomodate it's hunting technique or did it's hunting technique come about because of a deformation from other fish with eyes on both sides of their skulls?" A "chicken or egg" kind of question.

In Christ, GB

I certainly did not interpret the OP as you did, but to each their own. Scientists are humans like anyone else, so we do lean towards anthropomorphisms and teleologic language where it isn't warranted.

But to the meat of your post, you are quite right. The initial mutations would not be a goal oriented process that is looking to create flatfish. Instead, the mutation allowed for the fish to possibly hunt better using its current technique, or allowed for a slightly different technique and a new niche. It is certainly possible that the ancestor of flatfish actually laid on its side on the ocean bottom with one eye on each side of the head. A mutation that allowed both eyes to scan the ocean above would certainly be beneficial for such a hunting strategy.

 

[juvenissun]

Not necessarily. As I said, we don't know the genetic basis of this adaptation in detail, so not sure if mutations cause big or small jumps in eye position.

If so, on what basis we can call it a "link"? Purely geometrical reason?

In fact, one major problem to me is why is "link" so rare? It is supposedly MORE survivable than the original fish and should have higher population.