How did the Amazon stingrays become stenohaline?

[ewurm]

My personal opinion is that the rays are of Pacific origin. If they were Atlantic origin then why are there many rivers that flow directly into the Atlantic (I know they all eventually flow into the Atlantic) that lack any rays? Rays seem to be more concentratd in the western parts of South American FAR from the Atlantic. Plus the Andes were formed very quickly.

Another personal opinion I have is, IF they swam UP the Amazon why arent there more FW rays in the world that have swam up other rivers?

Too bad sharks did survive the transition to FW after they were trapped too....

I agree with you even with my limited understanding and lack of degrees. I think a marine incursion would be possible if the rays had a reason to invade (lack of food in their natural range), and if that reason continued for a very long time. That's the only way I could support the marine incursion theory.

 

[ewurm]

Too bad sharks didn't survive the transition to FW after they were trapped too....

Aren't there a species of shark that lives in the amazon in freshwater? I don't believe the instances are related, but I believe that is the case.

 

[JD7.62]

Aren't there a species of shark that lives in the amazon in freshwater? I don't believe the instances are related, but I believe that is the case.

Bull sharks can and do swim into freshwater but are not considered truely FW sharks. They only sp of sharks that are 100% FW sharks are sp in the Glyphis (spelling) genus of SE Asia and Northern Australia.

 

[ewurm]

Bull sharks can and do swim into freshwater but are not considered truely FW sharks. They only sp of sharks that are 100% FW sharks are sp in the Glyphis (spelling) genus of SE Asia and Northern Australia.

I'm sure I read here that there is a lake with sharks that live in freshwater, and I thought it was in the Amazon. I'll see if I can find it.

 

[JD7.62]

Aren't there a species of shark that lives in the amazon in freshwater? I don't believe the instances are related, but I believe that is the case.

I'm sure I read here that there is a lake with sharks that live in freshwater, and I thought it was in the Amazon. I'll see if I can find it.

Bulls inhabit Lake Nicaragua in Central America but they have easy Access to the Atlantic. There is a lake in Africa that "Zambezi" (also bulls) sharks inhabit that is pretty landlocked I believe.

 

[ewurm]

Bulls inhabit Lake Nicaragua in Central America but they have easy Access to the Atlantic. There is a lake in Africa that "Zambezi" (also bulls) sharks inhabit that is pretty landlocked I believe.

Looks like you are right. This article does say that some of the Bull Sharks complete their life cycle in freshwater. Perhaps I read that there are bull sharks that got trapped in a lake teporaily due to the high water- low water transition?

http://www.elasmo-research.org/education/topics/p_fw_rays.htm