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Author Topic:   Electric Fish on Verge of Evolutionary Split
CK
Member (Idle past 4127 days)
Posts: 3221
Joined: 07-04-2004


Message 1 of 9 (317301)
06-03-2006 5:59 PM


quote:
Electric fish emit weak signals from an organ in their tails that serves as a battery. Different emissions signal aggression, fear or courtship.
While the fish can apparently understand each others' warning signals, "They seem to only choose to mate with other fish having the same signature waveform as their own," explains neurobiologist Matt Arnegard of Cornell University.
But in the Ivindo River in Gabon, Arnegard and colleagues have found fish with the same DNA emitting distinctly different signals. The fish are likely on the verge of splitting into two species, the researchers announced today.
"We think we are seeing evolution in action," Arnegard said.
Electric animals
Because electricity is easily transmitted in water, many species of amphibians and fish have adapted to detect weak electric signals. Some, like sharks, use it to find prey. Others, like the electric eel, generate deadly voltages for defense or to kill prey. Others emit and detect electrical signals primarily as a means to communicate with their own kind.
http://news.yahoo.com/...ctricfishonvergeofevolutionarysplit

Replies to this message:
 Message 2 by Damouse, posted 06-03-2006 6:50 PM CK has not replied
 Message 6 by Ben!, posted 06-03-2006 7:11 PM CK has not replied
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Damouse
Member (Idle past 4905 days)
Posts: 215
From: Brookfield, Wisconsin
Joined: 12-18-2005


Message 2 of 9 (317321)
06-03-2006 6:50 PM
Reply to: Message 1 by CK
06-03-2006 5:59 PM


Nice!
Great example of Microevolution becoming Macro.

-I believe in God, I just call it Nature
-One man with an imaginary friend is insane. a Million men with an imaginary friend is a religion.
-People must often be reminded that the bible did not arrive as a fax from heaven; it was written by men.
-Religion is the opiate of the masses

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Replies to this message:
 Message 3 by Faith, posted 06-03-2006 6:56 PM Damouse has replied
 Message 8 by rgb, posted 06-03-2006 11:40 PM Damouse has not replied

  
Faith 
Suspended Member (Idle past 1444 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 3 of 9 (317325)
06-03-2006 6:56 PM
Reply to: Message 2 by Damouse
06-03-2006 6:50 PM


Re: Nice!
What on earth would make such a happening "macro?" Changes and adaptations are common and are all micro.

This message is a reply to:
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Damouse
Member (Idle past 4905 days)
Posts: 215
From: Brookfield, Wisconsin
Joined: 12-18-2005


Message 4 of 9 (317330)
06-03-2006 7:02 PM
Reply to: Message 3 by Faith
06-03-2006 6:56 PM


Re: Nice!
Macro in the sense that they will become a new species.
small changes add up untill one species is larger, has longer gills, doesn't use electricity, ect. and then you have two species and then you have a new species
Edited by Damouse, : No reason given.

-I believe in God, I just call it Nature
-One man with an imaginary friend is insane. a Million men with an imaginary friend is a religion.
-People must often be reminded that the bible did not arrive as a fax from heaven; it was written by men.
-Religion is the opiate of the masses

This message is a reply to:
 Message 3 by Faith, posted 06-03-2006 6:56 PM Faith has not replied

Replies to this message:
 Message 9 by Brad McFall, posted 06-04-2006 2:39 PM Damouse has not replied

  
AdminBen
Inactive Member


Message 5 of 9 (317335)
06-03-2006 7:07 PM


Thread moved here from the Links and Information forum.

  
Ben!
Member (Idle past 1398 days)
Posts: 1161
From: Hayward, CA
Joined: 10-14-2004


Message 6 of 9 (317338)
06-03-2006 7:11 PM
Reply to: Message 1 by CK
06-03-2006 5:59 PM


"They seem to only choose to mate with other fish having the same signature waveform as their own
vs
But in the Ivindo River in Gabon, Arnegard and colleagues have found fish with the same DNA emitting distinctly different signals. The fish are likely on the verge of splitting into two species, the researchers announced today.
Is it that people have different criteria for speciation?
From the way things sound, there's already been a speciation event via reproductive isolation. Or does the "official" speciation happen only after the DNA pools between the reproductively isolated groups change "significantly"?
Thanks!
AbE:
The process of splitting one species into two is called speciation. Scientists figure there are two ways it can happen. Groups can become geographically separated and take on new traits as their genes mutate. Or, animals can stay together but for some reason mate selectively to form distinct groups.
My bold.
They do go on to mention that the second type of speciation is "controversial." But it seems the article takes the perspective that that is what's happening here. So it seems to me they should be saying that speciation has occurred.
I'm probably just talking semantics here. But I'm not sure.
Edited by ! ben !, : added final quotation and question

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ramoss
Member (Idle past 611 days)
Posts: 3228
Joined: 08-11-2004


Message 7 of 9 (317362)
06-03-2006 9:29 PM
Reply to: Message 1 by CK
06-03-2006 5:59 PM


Shocking, I say, Just shooking.

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rgb
Inactive Member


Message 8 of 9 (317408)
06-03-2006 11:40 PM
Reply to: Message 2 by Damouse
06-03-2006 6:50 PM


Re: Nice!
Damouse writes
quote:
Great example of Microevolution becoming Macro.
I don't think this is enough to convince anyone that hasn't already been convinced by previous evidence. The only way you're going to see some acknowledgement from the other side is if you find an electric fish giving birth to a bear or something like that. And even then, you're going to have a hard time finding a so-called transitional that has a bear head and a fish fin.

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Brad McFall
Member (Idle past 5032 days)
Posts: 3428
From: Ithaca,NY, USA
Joined: 12-20-2001


Message 9 of 9 (317616)
06-04-2006 2:39 PM
Reply to: Message 4 by Damouse
06-03-2006 7:02 PM


Re: Nice!
There is no doubt that Carl's group is of the opinion that behavioral actions predate speciation in the fish. It was always the mantra that only same kinds respond to the same signals. I worked form Carl in the 80s. I never saw the *behaviroal* evidence for this. Back in the 80s the lab got the first species to breed in captivity and I had gotten the impression that the conclusion came from this one species that Jud Crawford coaxed and I kept feeding. I learned from the same lab tech there, now two decades later, that they have never got any other fish to breed in captivity to my surprise. Additionally, if it was so important that the waveform signal determines sexual (species) selection, then it seemed to me to be the next step was to see if there was an additional layer of variation *chemically* that might underlay the sex difference PER species difference in signalling. Carl balked at my suggestion to pay close attention to the solutes that make up water conductivity and as far as I know he never proceeded to investigate the carriers of the signal information (in the water) for biological activity.
I am having some problems downloading the pdfs@
Page not found | Department of Neurobiology and Behavior
but I do not see how they can conclude from same DNA - different waveforms, that this difference does not simply reflect ecological differences.
The one thing that Jud and I learned about e-fish reproductive behavior in the field (in Africa) was that the adults swam UNDER the forest floor to spawn in and around tree trunks BELOW the floor and that the young susequently returned to the lake to mature. So when determining where the possible boundaries of allopatry and sympatry are in these fish, the differences can be as diverse as the central forest rather than the lake proper. I noticed that an allopatric possibility remained through categorization of the adult habitats with minor scale color variations but when it came to species identification Carl destroyed this recorded information when he sent the specimens to Paris.
Subsquently, the lab took up the DNA work but I doubt the analysis would be as fine as the combined morphological and geographic approach I undertook for the family. The claim is probably more bluster than content. If they have behavioral evidence to indicate that the electric differences are not reflections of the larger diversity of equatorial life than temperate areas but ARE due to behaviorally influenced sexual selection and community effects then I might change my mind. My sense is that reading the PDFS can not change this opinion.

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