Paracheirodon Axelrodi, Two Species?

[Byron Hosking]

In Aqualog News, issue 7 [mid-1990’s] there was a report by Erwin Schraml on two distinct “forms” of the cardinal tetra, Paracheirodon axelrodi. The form from Brazil [Rio Negro and tributaries] has differences from the “Columbian” form [Rio Orinoco system] with respect to the neon line, the red/silver colouration and the overall thickness of the body. Schramel stated that Jacques Gery had been consulted and confirmed they are indeed two morphologically different forms, and further research would be undertaken in the future to determine whether the two forms are different species, subspecies or variants of one species.

I have both forms in my aquarium, and they are definitely different in their appearance. After a fair bit of online searching to see if anything further was done, all I have so far found is a comment by Matt Clarke on the Practical Fishkeeping site that there may be two species, a Columbian and a Brazilian. I posted a question there but nothing so far.

Is anyone aware of further information concerning this issue?

Byron.

[David Marshall]

Hey Kermit

If you go onto the Petfrd website and do a Neon tetra search you will find a piece by a member called BojanD (not me but a young man from Slovakia) which goes into this subject on some detail.

Regards David

[Matt Clarke]

I believe Heiko Bleher has covered a new species of Paracheirodon in Practical Fishkeeping within the last year or so, though I don’t recall which issue I’m afraid. I think it’s a different fish entirely though. It’s from the Rio Purus.

The two different Paracheirodon populations are covered in a paper in a book published by Project Piaba. They’re from the Rio Negro and Orinoco respectively. I’m afraid I don’t have the book with me but it does mention a few differences I believe, and I have a feeling that the may also differ slightly genetically.

[Matt]

Hey Byron all I have is from Weitzman and Fink:

“For the most part our sample sizes are small and not suitable for studies of intraspecific variation. However, some variation seems evident in the number of fin rays, scales and gill rakers. As an example, using a two-tailed test and square root transformations in computing value of t, we found significant differences (P < 0.01) in numbers of branched pectoral-fin rays, branched anal-fin rays, predorsal scale number, and ventral-limb gill raker counts in population samples from Tapurucuara, Rio Negro, Amazonas, Brazil (n=48) and Morocoto, Río Orinoco, Amazonas, Venezuela (n=13). A study of the significance of this sort of variation in P. axelrodi in relation to geographic distribution must await intensive collections of samples throughout its range.”

This was in 1983 and I have no idea if further studies have been conducted since. David are you sure ‘BojanD’ isn’t your hip-hop alter ego by the way? 😀

[Byron Hosking]

Thanks David, Matt and Matt. [Matt Clarke, am I correct in assuming you are the editor of PF? Just to satisfy my inquisitiveness.

Author

Posts

[Author]

Posts