Fish Fetish
Animals are attracted to many different characteristics in nature. Peacocks attract a female using their bright and colorful plumage. American Robins attract a mate with their bright red breast. Some birds attract mates by calls. These are but some of the sexual dimorphisms which exist in the animal world. But would you believe that something as simple as color preference could lead to two different species of fish living together?
Cichlids are a type of fish which live in Lake Victoria, bordering Uganda, Kenya, and Tanzania. The females of these fish prefer males of different colors leading to two different species: the red and the blue cichlids.
It is though that these two types of fish evolved based on the depth of the water in which they lived. The blue fish lived closer to the surface of Lake Victoria where their blue color would make them more visible to the females of the species and therefore more able to mate. The red fish on the other hand lived at a deeper depth where, due to there being less light, their red color would be more visible. This is because the fish at these depths have retinal pigments which are more sensitive to these wavelengths of light. The males therefore evolved to fit the females tastes. After this the, two colorations would cease to interbreed leading the two separate species.
It is very interesting that the two species would have completely separated simply because of choice of coloration. Not only this, but this occurred while living in almost exactly the same habitat, with no environmental factors keeping them separate. It is very interesting that the fishes' retinal pigments can evolve to match their visual environment.
http://sciencenow.sciencemag.org/cgi/content/full/2008/1001/2
Posted by: Alex Jackson
Cichlids are a type of fish which live in Lake Victoria, bordering Uganda, Kenya, and Tanzania. The females of these fish prefer males of different colors leading to two different species: the red and the blue cichlids.
It is though that these two types of fish evolved based on the depth of the water in which they lived. The blue fish lived closer to the surface of Lake Victoria where their blue color would make them more visible to the females of the species and therefore more able to mate. The red fish on the other hand lived at a deeper depth where, due to there being less light, their red color would be more visible. This is because the fish at these depths have retinal pigments which are more sensitive to these wavelengths of light. The males therefore evolved to fit the females tastes. After this the, two colorations would cease to interbreed leading the two separate species.
It is very interesting that the two species would have completely separated simply because of choice of coloration. Not only this, but this occurred while living in almost exactly the same habitat, with no environmental factors keeping them separate. It is very interesting that the fishes' retinal pigments can evolve to match their visual environment.
http://sciencenow.sciencemag.org/cgi/content/full/2008/1001/2
Posted by: Alex Jackson
Update
To clarify: visually, the main difference between males and females is that females have a yellow pigmentation. Also, the females are not simply attracted to more colorful males. Rather, there are two different types of females in the lake: those who are attracted to red fish and those who are attracted to blue fish. The females' preference is supposed to be based on what color is easiest to see at the depth they are most used to. In response to the two color preferences, the males are evolving their coloring towards these two colors to suit the preference of the females. If the fish were to be some other color (such as purple), because the females are not attracted to that color they would not be able to reproduce. Because the males are evolving their color to match female preference this is a type of sexual selection. The comparison to Peacocks holds true in this case because Peacocks have evolved their bright and colorful plumage in a similar manner. They are more likely to attract a mate if they were brightly colored (which outweighs the disadvantages such as being more likely to be killed by a predator) so they evolved into the more brightly colored birds we see today. Their plumage does not in fact play any role in mating, but it plays a vital role in attracting a mate.
posted by PWH @ 10:07 PM
6 comments
6 Comments:
I though this was an interesting article, especially because species divergence is something I have read a lot about. I am a little confused as to how the females choose which fish to mate with. I understand that red is easier to see down below and blue up top, but do the females chose their mate based on where they happen to be in the water at that time? Also, the article implies that the males "take on" the blue or red hue around mating time, do they change their scale color throughout the mating season? If so, how could they do that?
-Julie Riley
How much farther do the red fish live from the blue fish? Are there two different types of female cichlids? Since, the fish in the deeper depths have retinal pigments that are more sensitive to the red light wavelength. The female that live closer to the surface would not need this trait to mate with blue fish.
Also, I read that the plumage of peacocks do not really play a vital role in mating. There is very little difference between the size and characteristics of the plumage.
SUSAN DUONG
I was wondering if you knew how deep into the lake you had to go to change from the blue to red coloration. Also I was wondering if there was a purple area in which other males could further diverge if that layer was thick enough. Do you know what makes the different colors in the water? You mention pigmentation for the fish but how about the water? Is this due to iron or nutrients, or just light? Also, you said the blue fish were easier to see in the blue water and the red fish were easier to see in the red water, wouldn't it be harder to see?
Ada Marie Flores
This is very interesting because it shows that the males realize that the females are choosing mates depending on coloration. But are there only red and blue fish? No other colors? Because if it was true that the males knew that the females were choosing depending on color, then i would think there would be many other colored male fish....
By having greater differentiation in color, it would create more competition and a greater chance that the female might pick them to mate.
Brena Sena
Nice article. I was curious to know about what separates the males from the females? Do they have the same pigmentation or do females have a different color than males. I was confused about the blue fish at the surface and what makes them more visible? Good work, I would like to know more.
Carlos A. Varela
first off very interesting title. and an interesting article. i used to work in a pet store that sold Cichlids and they are very interesting. trust me it was more fun to watch them than work. however it is a nice example of specialization.
-Matthew Sousa
Post a Comment
<< Home