# Serrasalmus Rhombeus



## CanadianKid92 (Apr 12, 2012)

Alright everyone I just want to know as much about my black piranha as possible! anything interesting you have to say or helpful just feel free to post!

SO heres a question I know my rhoms eyes will change colour around 4-6 inches or so. But once this process starts how long does it take for them to fully turn red? is it right away or is it over multiple months?
?


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## memento (Jun 3, 2009)

That varies... you have many different geomorphs in S.rhombeus.
The redness is the eye is a result of the development of a reflective layer on the retina, that enhances nighttime vision and makes it possible for them to see infrared waves humans don't see.

In some specimen it's mostly a red hue, in others the eye gets really bright red.


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## CanadianKid92 (Apr 12, 2012)

so theres peruvian, brazillian and venezuelan. and from each different region there are a vary in morph. From White piranha to jet black piranha to diamond piranha. and iv heard of a couple other different ones. there all the same fish, just have addapted different to their environment thus the sleight differences in appearance/color?


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## memento (Jun 3, 2009)

S.rhombeus is actually a complex of species that have not yet been described seperately. There are at least 5 cryptic species.
But as long as those are not described rsseperately, my motto is "a rhom is a rhom".

Yes, there are several morphological varieties which are, scientifically seen, all the same species. Parallel evolution can cause populations of a same species devellop with different characters


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## PiranhaMan777 (Apr 25, 2012)

So there's three types s.rohm Peruvian, Brazilian and Venezuelan. I know you say "a Rohm a Rohm ". But is their any difference between them??? Cause I have a Peruvian s.rohm. And I'm curious to know if he will turn jet black too???


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## memento (Jun 3, 2009)

"A rhom is a rhom" is the statement that has been held up to avoid more confusion regarding the so-called varients.
To be honest, in my opinion it's time to drop that statement.
"Rhombeus" has become the ADHD of piranhas. Everything resembling it and not fitting another known species, gets labelled rhom nowadays.
One of the recent specimen that got identified as rhombeus had, as Mr.machado described it, "an unusual body pattern, something I agreed with. Nevertheless it got labelled rhom without any doubts...

Fact is, rhombeus is a complex, fitting at least 5 undescribed species. So not every rhom is the same of course.
Problem with that is however, though most rhom keepers agree some look completely different from each other, the only scientific evidence backing this up are 5 different types found in DNA.
So when we stick to science, a rhom is still a rhom for there's only one species description. Even though Merckx described four different populations which are all different in morphology...

So back to your question - yes, there are differences between them. However it's impossible to tell yet if those are because they in fact are different species, or just differences caused by geographical differences.
Nor is it safe to say all Peruvians grow to be Jet Blacks, for it's not known if different cryptic species share geographical ranges.

Interesting detail to this discussion is an article Bleher published recently. I regret the fact that it had been published without any scientific evidence backing it up, but he mentioned 6 unidentified species. One of them is obviously wrong for it's a breeding adult, but the other 5 all look different from each other.
I'm not saying these indeed are some of the cryptic species within the complex of rhombeus, but nor am I rejecting the possibility he could be right.

Have a look at the profile I wrote onS.rhombeus. Intend to update it one of these days.


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## PiranhaMan777 (Apr 25, 2012)

Thanks that's was very interesting! I like the profile you wrote thanks.. I'm trying to get real good understanding of these species since that I have s. Rohm.. Thanks..


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## s4awd (Mar 28, 2011)

I was just like you a year ago. Was pretty excited about them but eventually learned that there isn't much to them. They swim up to you to eat, gulp some pellets and go back to their spot. I bought a 2 inch Peruvian and a 7 inch Xingu. The Xingu's eyes were already red. Rhoms are rhoms. In terms of shape, they all look the same when they're well fed. You can see differences when they're very lean but once you feed them they tend to look the same. As for color, my Peruvian which was sold as a blue it turning out to just be a plain black but I'll wait a few years to confirm before i start complaining to aquascape lol. The xingu was silver and still silver. My Peruvian's eyes started to get a tinge of red at 4 inches after 8 months of having him but by then I was already so out of my piranhas. zzzz


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