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Paracheirodon Axelrodi, Two Species?
June 24, 2009
6:56 pm
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Byron Hosking
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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.

Byron Hosking, BMus, MA Vancouver, BC Canada
June 24, 2009
9:19 pm
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David Marshall
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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

June 24, 2009
9:48 pm
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Matt Clarke
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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.

June 24, 2009
10:29 pm
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Matt
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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? Laugh

Cake or death?
June 24, 2009
11:20 pm
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Byron Hosking
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Thanks David, Matt and Matt. [Matt Clarke, am I correct in assuming you are the editor of PF? Just to satisfy my inquisitiveness. /unsure.gif" style="vertical-align:middle" emoid=":unsure:" border="0" alt="unsure.gif" />]

The Bojhan post concerns the fourth "neon" that Heiko discovered in 2006 and that is I suspect the same as the new species in PF. I read about this in TFH, Heiko had two successive articles on the four neons in the September and October issues of (I think) 2008. From what I've been able to find, it has not yet been named, but Myers did DNA and confirmed it as a fourth species related to the other three. Heiko's collected fish were sent to Dr. Gery whose health was giving out and then to another scientist who suffered a stroke; this fourth neon seems to be the harbinger of bad fortune.

I think the Project Piaba info is on the two cardinal tetras. I found their website and will do more searching. Thanks Matt for this lead.

Byron Hosking, BMus, MA Vancouver, BC Canada
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