Saturday, October 04, 2008

Fish, This Ain’t Your Side of the Lake, This is Crip Territory!

The cichlids living in Lake Victoria (near Kenya) have divided themselves into red and blue “worlds”. Organic filtering material in the lake removes blue light, causing the deeper parts of the lake to appear red, while the shallow parts are not as affected and remain blue. Apparently, the males of this lake have either blue or red coloration. The female cichlids (which are all yellow) have a preference as to which color male they mate with. The females from the shallow, blue regions prefer blue males; and the females from deep, red areas like red males.

Dr. Ole Seehausen, of University of Bern in Switzerland, along with his colleagues, recently published a paper in Nature on the separation of this species. They found that the retinas of these fish have adapted to favor the colors of their environment. So, the blue fish see in blue, and the red fish see in red. This alteration in perception may be causing the one species to become two! Evolution often looks at various isolations causing a species to evolve in different directions, but it is surprising that living in different depths of the same lake could lead to speciation.

Some question whether or not this can actually be considered the creation of a new species. According to Trevor Price, an evolutionary ecologist, there is not enough evidence that the one population has divided into two species.

Whether or not you believe that one species is becoming two, it certainly is interesting to see this dramatic division in environment, perception, coloration, and preference.



http://www.nytimes.com/2008/10/07/science/07obfish.html?_r=1&em&oref=slogin

http://sciencenow.sciencemag.org/cgi/content/full/2008/1001/2

Posted by Cecelia Hunt (3)

14 Comments:

At 5:59 PM, Anonymous Anonymous said...

This is a bit different because the fish have no way of choosing a mate based on genetics, it is based on the enviroment. Are there any other factors in choosing a mate for this particular species of fish? Also have they tried to mate the two different species in a lab without any coloration? A very interesting article.


Duy Nguyen

 
At 8:59 PM, Anonymous Anonymous said...

How can the scientist tell what color the fish can see in? Or do they just assume that the blue see blue and the red see red?
-Sasha Rogers

 
At 8:05 AM, Blogger PWH said...

In the deeper parts of the lake the males are red and in the shallower parts they are blue, but then later you say that the blue fish see in blue and the red fish see in red. Does this mean that if a blue fish were put farther down they would still see in blue until they evolved into a red fish? Also, the females are yellow so if they are put in different water with red and blue fish which colors would they end up seeing and then which would they choose to mate with?

-Tara Quist

 
At 3:57 PM, Blogger PWH said...

This type of selective breeding is interesting, but besides the coloration and retina alteration, are there any other differences within the two groups of fish? Have there been any genetic tests that show the DNA differentiating between the two groups of fish?

-Kiel Boutelle

 
At 5:21 PM, Blogger PWH said...

This is an interesting article that touches base on the evidence for speciation. I was wondering whether it was just a matter of preference that the red-seeing and blue-seeing cichids could not mate. Also, are there any other things that could validate categorizing them as two different species other than the preference in color?

Helen Thi

 
At 6:40 PM, Blogger PWH said...

Can something as small as vision make one species seperate from another. If everything else is identical a slight vision alteration doesn't seem like that big of a deal but if it influences their breeding habits I guess it can eventually cause two species to appear out of one. Also, do the blue fish ever mate with red fish or vice versa.

Patrick Salome

 
At 7:54 PM, Anonymous Anonymous said...

Interesting...I have been learning a lot about what defines a species in my evolution class. So I'm curious as to whether or not these fish can actually successfully breed despite the coloration?

Ericka Adey

 
At 8:21 PM, Anonymous Anonymous said...

Wow. Nice article. Did it mention how long over time it took for the difference in color of the fish and seeing to take. I wonder if u took the two "different" species in a tank if they would eventually revert back to being just one species.
-Alex Pavidapha

 
At 8:27 PM, Anonymous Anonymous said...

Very interesting, though I noticed there is no mention of a time frame. How long did it take for these adaptations to occur? Also, what additional evidence is necessary to classify these two populations as two species?

-Jane de Verges

 
At 8:46 PM, Blogger PWH said...

Sexual selection was probably the sole influence of the change in male coloration. If the article mentioned sexual selection, did it say how long of a time period it took for the change to occur?

Jimmy Sullivan

 
At 9:54 PM, Blogger PWH said...

Is the only difference between the 2 sub populations is the preference in color of mate and adaptation of the retinas in their eyes? Or are there other differences in behavior?


-Joe Alonzo

 
At 11:14 PM, Anonymous Anonymous said...

Its very interesting that the fish in the lower part of the lake are red and not vice versa. I say this because water's natural property is to filter colors by the order of red, orange, yellow, green, blue, indigo and then violet. Since red begins to "vanish" in depths lower than roughly 20 feet I'm assuming that the blue layer is very close to the water's surface, which means that the whole separation must exist in a very narrow "strip" of water (depthwise).
regardless- the gang analogy was awesome!

Noam Pelleg

 
At 10:56 PM, Anonymous Anonymous said...

Hey, Thanks for all the comments!! You all asked a lot of really good questions, and I don't have the answers for all of them. This research was recently published in Nature (it made the cover). My sources of information were magazine articles summarizing the original paper. Unfortunatly, I do not have a subscription to Nature, and don't have access to that actual article.

As far as I can tell, the only factors for choosing a mate were color. This seems to be a preference, yes, but only because of the physiological differences in eyes. I did also get questions about whether they are capable of cross breeding, and I believe that they do not breed. I think that if they were capable of it, the researchers probably would not be suggesting speciation. At the very least, they choose not too breed.

The articles said that there were alterations to the fishes retinas, so this is how they could tell about sight differences. There was no mention of time in the articles I read, but that would be interesting to know.

A lot of you asked about how this can realy be counted as speciation. I believe that this conclusion is still very much up for debate. Many feel that this is not enough of a qualification. The key is that they have reproductively isolated themselves from each other. And if they are not cross breeding, they probably either are or will become two species.

Also, thanks for getting my pun, Noam

Cecelia Hunt

 
At 2:44 PM, Blogger PWH said...

What determines if a species is divided into 2 new species?

Jennifer Smith (3)

 

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