
Originally Posted by
XnSdVd
But how much does body structure vary within the singaporean population? That and since you brought it up. Why is it most books refer to them as Barbus? Oh and Is Boraras the proper genus for rasboras? And would you mind explaining the difference between puntius and systomus? And is johorensis a seperate species or the old name?
johorensis is a different fish from hexazona, the scientists made a mistake 
here I reproduce what Ng Heok Hee (a Singapore scientist now at Michigan studying for his PhD) said about Systomus and also the confusion of johorensis and hexazona:
First the issue of Systomus vs. Puntius. Systomus was resurrected as a valid genus by Walter Rainboth, who used it for small barbs with a serrated dorsal-fin spine, 2 or 4 barbels, and less than 12 gill rakers on the first gill arch. In contrast, Puntius would have a smooth dorsal spine, only 2 (never 4) barbels, and more than 12 gill rakers on the first arch. So, by this definition, many of the barbs encountered in the aquarium trade are Systomus (S. tetrazona, S. binotatus, S. hexazona, S. partipentazona, S. johorensis, S. gemellus, and so on...).
Of course, this scheme is not adhered to by all workers, so some references (notably those of Kottelat) still refer to these as Puntius.
Next, the identity of the six-banded barb. The correct name should be S. hexazona. The six-banded barb has long been misidentified as Systomus (Puntius) johorensis. However, the name S. johorensis actually applies to the barb that is commonly identified as Systomus (Puntius) eugrammus (the striped barb), a much larger species. Part of the confusion lies in the fact that young S. johorensis have a barred pattern very similar to that of the six-banded barb (the vertical bars break up with age and become horizontal stripes instead).
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