A few random pictures from the past week or so

[Innesfan]

No i could ask but not sure they really know - they were sold as 'gold' marginatus and they definitely have more colour than the non 'gold' sort - also i'm noticing an odd bluish patch just behind the dorsal fin on the top.

Interesting. The species is polychromatic and there is tremendous variation color-wise among N. marginatus populations. Their range is enormous, from the Guiana Shield countries in the north through the entire Amazonian Basin from Peru and Colombia in the west to the Brazilian Atlantic Coast in the east, and that has resulted in many color morphs. Rumor has it the splitters will soon break up the species and elevate numerous color morphs to individual species.

 

[anewbie]

Interesting. The species is polychromatic and there is tremendous variation color-wise among N. marginatus populations. Their range is enormous, from the Guiana Shield countries in the north through the entire Amazonian Basin from Peru and Colombia in the west to the Brazilian Atlantic Coast in the east, and that has resulted in many color morphs. Rumor has it the splitters will soon break up the species and elevate numerous color morphs to individual species.

no.... we ahve enough species

 

[gwand]

What are the current criteria for defining a distinct species in freshwater tropical fish?

 

[Innesfan]

What are the current criteria for defining a distinct species in freshwater tropical fish?

That depends on what school of ichthyological thought you subscribe to-- whether you are a splitter or a lumper.

In the case of Nannostomus, Stan Weitzman's revision of 1975, which has pretty much been universally accepted and has held to this day, reflected his views as a lumper and he did not find enough divergence among N. marginatus populations, for example, to justify splitting them up. Now we have the complicating addition of dna data which is not always as illuminating as one would hope and is sometimes actually confounding. For example, I have been told that there is more dna divergence among N. beckfordi populations than there is between some of the Nannostomus species.

But I do believe that now that Stan is gone, and dna data is increasingly more a factor, you are about to see an explosion in the number of Nannostomus species and, for that matter, tropical fish species in general. In fact, I predict Nannostomus itself will be broken up into other genera. I would love to be wrong about this.

@anewbie: I agree with you!

 

[gwand]

I have not thought about speciation since my genetics course in medical school. Back then if two animals were of different species they could not produce fertile offspring. I guess we have come along way from that definition.

 

[Innesfan]

I have not thought about speciation since my genetics course in medical school. Back then if two animals were of different species they could not produce fertile offspring. I guess we have come along way from that definition.

Indeed, witness in our own genetic backyard--Homo sapiens x Homo neanderthalensis.

 

[gwand]

I know some people who are more homo neanderthalensis than h. sapien.