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I've had this guy for a little over a year and a half. he's about 2 years old now. almost 4". is he a rhom? he's pretty active and aggressive. here are some pix from beginning to now. thanks guys.
 

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what size tank do you have because you said that he is about 2 years....... right........ is
the picture you show is now or a year ago because 2 year piranha would be a hand size or bigger............... just wondering???????????????
 

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Discussion Starter · #8 ·
he is in a 30gal and he always has guppies in his tank and he eats small goldfish and pellets. he is fed daily and he eats infront of me so i know he eats well. i feed all of my fish daily. i have to clean more often but i think its worth it. he was sold as a rhom by an lfs, but i will have to wait till he gets bigger. thanks all
 

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The problem with juveniles rhombeus-group fishes, occasionally Pristobrycon can fool even experts in thinking what they are looking as S. rhombeus, which is my hesitation on being 'fairly' certain. The extra photos you've posted make me hesitate because a couple of them look "pristobrycon-like". The bars, spots and head shape put it in that area.

Allow it more time to grow out and keep a good catologue on its growth. I'd like to revisit your fish again when its grown more.
 

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Looks like that fish has a "Manueli-style" caudal fin - no dark terminal band and a prominent V at the base.
I thought Rhoms had more Nattereri-like tails, dark terminal band and base, without the distinct V-shape (I know, the comparisons are hardly scientific, if at all, but it's the easiest way to compare, imo.)
Could it be because of the size of the fish - 4" for a 2-year old Rhom doesn't seem much to me...

Or am I just way off?
 

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Judazzz Posted Today, 12:14 PM
Looks like that fish has a "Manueli-style" caudal fin - no dark terminal band and a prominent V at the base.
I thought Rhoms had more Nattereri-like tails, dark terminal band and base, without the distinct V-shape (I know, the comparisons are hardly scientific, if at all, but it's the easiest way to compare, imo.)
Could it be because of the size of the fish - 4" for a 2-year old Rhom doesn't seem much to me...

Or am I just way off?
I'll answer it this way, some subadult Serrasalmus rhombeus have a dark "V" at the caudal and a faint band at the tail until past subadult. The compressus group, in particular S. altuvei can have a dark "V" at small sizes later grow out and have a dark band just like S. rhombeus. Pristobrycon can have both a dark "V" and a terminal band depending where they are in age. Its very interchangeable. That's why some compressus group fishes are mistaken for S. marginatus which predominately has a dark "V" throughout its life until maturity when the tail darkens nearly completely to just a hyaline edge (like S. maculatus). ON his photos, I'm thrown by the added photos of what appears to be a Pristobrycon.
 

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Judazzz Posted Today, 12:45 PM
Aaah, I see...
Thanks for clearing that up, Frank
One last thing, Antonio Machado when he revised the genus/species of S. eigenmanni made a remark that this species confused him because of the ontogeny, meaning the strong resemblence to a Serrasalmus species (rhomboid body, pointy snout) to later developing into a Pristobrycon appearance (small snout, laterally compress body).
 

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hastatus said:
One last thing, Antonio Machado when he revised the genus/species of S. eigenmanni made a remark that this species confused him because of the ontogeny, meaning the strong resemblence to a Serrasalmus species (rhomboid body, pointy snout) to later developing into a Pristobrycon appearance (small snout, laterally compress body).
[snapback]851096[/snapback]​
oh, now you come around


http://www.piranha-fury.com/pfury/index.ph...topic=29027&hl=

From last year
 

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Come around to what?

PiranhaMaster Feb 9 2004, 10:14 AM

ok, first it is way too small for an ID but that being said it does not appear to be S.Rhombeus at this time. There are many varients of S.Rhombeus so only time will tell. By just looking at this very small specimen with rounded snout and very large eye I am going to GUESS that it is in the Pristobrycon Genus. Possible eigenmanni. Again at this stage in it's development there is no way to be certain and may infact look completely different with another inch or two added.

Does yours look just like this one? and is yours the same size at 6 months? That is a very slow growth rate for any P no matter what type it is. There are no tell tail signs at this stage to make any possitive ID. I only notice the eye and snout as not looking like a typical S.Rhom.

hastatus Feb 9 2004, 10:33 AM
S. rhombeus. As to type of locality fish is from, can't say, to young.

PiranhaMaster Feb 9 2004, 10:45 AM

Well at this stage I obviously disagree with Frank but he is the resident expert on this so I would assume him to be correct if I were you. Just note my opinion and we will see as it developes. I have 6 rhom varients all at 3-4" now but started at 2" and none of them share the look of your fish. As I said there are many varients so it could be but time will tell. As of now I would say.

hastatus Feb 9 2004, 10:59 AM
Enjoy: Photo taken from Schulte Piranhas in the Aquarium. Photo by H.R. Axelrod.

I don't have juvenile photos available of similar S. rhombeus "appearance". But you'll just have to take my word for it.

PiranhaMaster Feb 9 2004, 11:04 AM

I am very familiar with this pic and it looks nothing like this fish in question except for the size of it's spots and that is not a definitive characteristic. Again it is way to small to even begin a debate on but I would have to agree to disagree at this point.

QUOTE
PiranhaMaster Posted on Feb 9 2004, 06:04 PM
I am very familiar with this pic and it looks nothing like this fish in question except for the size of it's spots and that is not a definitive characteristic. Again it is way to small to even begin a debate on but I would have to agree to disagree at this point.

hastatus Feb 9 2004, 11:07 AM
Let's hope the fish lives long and propers to void this debate eh?

hastatus Feb 9 2004, 11:19 AM
QUOTE
PiranhaMaster Posted on Feb 9 2004, 06:15 PM
Eye, Snout, Tail, Head are all very different
PiranhaMaster Posted on Feb 9 2004, 06:14 PM
I agree. I just made this for a quick comparison. Not trying to drag out this topic any longer though.

Understand. Welcome to growth morphology studies.

QUOTE
phil Posted on Feb 9 2004, 08:59 PM
doesn'tlook like a rhom to me, it has large eyes,a nd a rounded nose, as Piranha Master pointed out

hastatus Feb 9 2004, 02:57 PM
What is not pointed out is the fish image was taken at a slight angle giving the nose that appearance. Which is why I have pinned that fish photos should be angle-free and flank photos only without deviation to avoid false positives for ID. I'll see if I can find the image of my own S. rhombeus that is identicle to the one shown by Chad_linden. As I said, we all can argue pro and con on this ID. Ultimately when the fish grows out then the proper ID will be made
.
 

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The big problem (that I have) in PID is to much usage of variable photos. If the hobbyist would just select 2 good (clear) photos w/o angle that would help so much more. In the case of the above photos, the chronological order is off and hard to tell in what order of growth (and age) they appear. Certainly looks like 2 different species being shown which clouds the issue more. I don't disagree much of PiranhaMaster regarding placement of the fish as a Pristobrycon. The issue is not being right on the "guess" as much as being able to get a good image to resolve the ID issue. My impression at the young ages was S. rhombeus in the original thread. Subsequent photos (if it is the same fish) begin to show tell-tale signs of bars and spots, consistent with compressus-group member. Yet the snout as it begins to develop more (and body) begins to laterally compress suggesting a Pristobrycon. Is it S. eigenmanni? Don't know without having the actual collection point as many of these humeralis-type fish are extremely close in appearance. So even if we can agree the fish in question is a Pristobrycon, it still leaves the question which species. And only time will reveal that based on how well the photos are taken and displayed.
 
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