Can anyone id this silver dollar?

Rdurha1

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I picked up the group of 3 of these guys about a month ago as surrenders from my LFS and they look nothing like my "normal" silver dollars. Any ideas on what sub species they are? Thank you guys in advance!20191203_155348.jpg
 

FJB

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Very nice! Excellent images.
- Certainly a Metynnis - Long (broad) adipose fin.
[Caveat: Silver dollar specimens in aquaria (i.e, no benefit of classical ichthyological characters such as scale counts, and ray numbers) are notoriously difficult to ascertain]
- The specimen at center is a male, in reproductive display coloration. The specimen at left (only posterior part visible) is another male of same species.
- The specimen at center showing only the eye and the anal fin is a female and may or not be the same species (additional images needed)
- Altogether, the male at center in my opinnion can only be one of 3 species: Metynnis altidorsalis, M. lippincotianus, or M. maculatus.
- I believe most likelly it is M. altidorsalis, the same as a male specimen I have (pictures attached, albeit not in breeding coloration). In my specimen the black ringing the causal and adipose fins, and spotting the dorsal, are not seen in the picture attached, but the specimen does show them in and on/off basis, mood depending. I also have specimens of what I believe are maculatus and lippincotianus.
- I stress, the female may or not be the same species as the other two specimens. A full photo would very nice.

Very nice pick! Thanks for sharing.

SilverDollars_29May2019_JESUS_M.altidorsalis_COMP.jpg
 

FJB

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I forgot to mention: Currently there are 15 valid species of Metynnis, specimens of an additional one (16th) remain undescribed). Five-six of these are available in the hobby, with 3-4 being the most commonly seen. This all is completely separate from the other (larger) genera of silver dollars (Myleus, Myloplus, etc.)

There are many other validly introduced names within Metynnis, now relegated to synonymy. As far as I know all are recognized at full specific rank (i.e, there are not currently accepted subspecies within the genus).
 
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Rdurha1

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Wow! Thank you for the response. The one hiding behind the darker SD is a diffrent species they were the original two I had in the tank. I really like how much darker the others are and the black edging on the fins!20191203_180634.jpg20191203_155245.jpg
 

Rdurha1

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And yes my Nicaraguanese and KK Blood Parrot are a very odd couple!
 

kno4te

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Look hypsauchen and argenteus.
 

FJB

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Thank you for posting a full image of the female (a fish you already had in your tank prior to obtaining the new ones).
M. hypsauchen is possible for the males but I don't feel it. I am posting one certified hypsauchen (not from me) for reference. But then, I don't claim expertise.
By the way argenteus is now considered under the synonymy of M. altidorsalis. As mentioned before many names have been created, which causes much confussion. Even though argenteus is one of the most commonly used names in the hobby (for SD's), it is a synonym of M. altidorsalis, a very variable species.
That, and the fact that most overwhelmingly often we do not know the locality of the fish, cant count scales and rays, and the fact that there are at least 3 sources of variability, makes recognition quite difficult. The 3 sources are: ontogenic variation (as they develop they change substantially in shape and coloration), sexual dimorphism, and intraspecific variation among individuals).
Finally, I am also posting three images of my female, which I think is M. maculatus. Her name is Jill, and she is approaching 20 years of age, the last 2 1/2 with me.
Beautiful fish, thanks, and good luck with them!

Metynnis hypsauchen (M&T) Male -75mm [Ota 2015 fig.57] LABELED.jpg

SilverDollars_29May2019_JILL_M.maculatusCOMP.jpg
 
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