Do smaller fish mimic similar species to fit in, like silver dollars?

[bettaMagenta]

I'm building a mixed shoal of silver dollars, started with the regular ones and they've grown to be the big guys, about 4 inches now. Got some tigers next, but only managed to get one at first, it's slightly smaller than the regulars - interestingly, its tiger striping was pretty faded at first but now it's really vivid. Not sure if the fish has grown or if there are others in the tank that are influencing it. Later on, I got three more tigers, they're pretty small, only about 1.5 inches, but they've got really vivid striping even at that size - maybe the bigger tiger in the tank is helping them out. This week I picked up some spotted silver dollars, got three of them, and when they came out of the bag they didn't have any markings due to stress. Three hours later, they all had tiger stripes - there's a slight size difference, they're the smallest in the tank, so I know which ones are new. Got them from a reputable mail order seller, so I'm wondering, did the spotted ones just blend in or did I get mislabeled tigers? I asked the seller about it, just in case the rest of his stock is the same, but haven't heard back yet.

[bettaMagenta]

Has anyone else ever seen this happen - I've got a bunch of small Tigers now, even though technically half of them are supposed to be Spotted...

[bettaMagenta]

Seller just got back to me, doesn't think spotted would start mimicking the tigers, said more likely the pickers grabbed the wrong ones... wants me to send some pics & he'll sort it out... he does have both in stock, so we'll see what he says after I send the pics...

[Emeraldsea]

I think it's pretty clear he just sent the wrong ones over. Spotted ones aren't gonna mimic the tiger pattern, so yeah, looks like a mix-up with the order.

[Bisco]

Agree with Emeraldsea, spotted ones don't mimic the tiger pattern. When discussing silver dollars, it's essential to be more specific about the species we're referring to. There are 14 recognized species in the genus Metynnis, and common names like "regular," "spotted," or "tiger" can be quite broad. To ensure we're on the same page, sharing pictures would be incredibly helpful.

Individual fish can look dramatically different depending on their mood and development stage. Some specimens may display stripes only at certain times, while others may show more or less spotting. Therefore, it's crucial to consider more stable characteristics for species-level identification.

I've had the opportunity to observe and learn from my own silver dollars. I currently have four different species in two tanks. I'd like to share some pictures to illustrate the diversity within the genus.

My "tiger" silver dollars, photographed in November 2021, shortly after I acquired them at about 2 inches in length. At the time, they were still juveniles and hadn't yet developed their adult characteristics.

Fast forward to May 2023, the same four fish had grown significantly in their new 125-gallon tank. The gender differences had become more apparent by 2022, with three males and one female.

More recently, I took some pictures of the same fish, now young adults at about 3.5 inches in length. The female, in particular, has grown to about 4 inches.

I also captured a photo of the female and one of the males showcasing their vibrant colors.

In my other tank, I have three different species of silver dollars, each with unique characteristics.

A closer look at some of the fish in this tank reveals a male Metynnis maculatus, as well as a Metynnis altidorsalis displaying its vibrant colors.

The spotted silver dollars, specifically the Metynnis lippincotianus, are also quite striking when they show off their colors.

I'd love to see pictures of your silver dollars, bettaMagenta. Sharing our experiences and observations can help us learn more about these fascinating fish.

[bettaMagenta]

Looks like this thread was tailor-made for you, I need to get some pics for the seller, so be on the lookout for those soon.

Getting good shots is gonna be a challenge, my tank's turned into a jungle with all the plants, and it's only accessible from my work area, which is pretty cramped - I've only got about 2.5 feet of space to maneuver. I'll do my best to get some decent pics, but no promises.

[bettaMagenta]

I'd have to corral the fish against the front of the tank to get a decent picture for identification. The first picture I took is of my larger tiger, and the second is of the two newer additions. I'm due for an upgrade on my cell phone next week, this one's an older model with some issues, so I'm hoping the new one will help me get some better shots.

[Bisco]

Nice. Those are indeed "tiger" SDs, Metynnis fasciatus, and they appear to be quite young. While the current photos are helpful, better pictures may aid in further identification. As it stands, it's likely that the fish are still too young to exhibit clear gender differences, specifically in terms of anal fin shape. Typically, females develop a redder anal fin at a relatively early stage, but this characteristic may not yet be apparent in your fish. Additionally, males tend to develop a red humeral spot later in their development, whereas the two black humeral spots are often visible in both males and females, albeit more prominent in males.

I'm intrigued by your mention of having at least one 'regular' and one 'spotted' SD. These groups are indeed where most taxonomic confusion arises among hobbyists, and I'd love to see photos of these fish when you have the opportunity.

[bettaMagenta]

I have 3 larger regular silver dollars, about 4 inches, and no spotted ones yet, still trying to get some. I may remove one or two of my regular ones, as one has a pretty big streak on its side, doesn't look like a growth, maybe a bacterial issue. Now that my quarantine and hospital tanks are up and running, I'll probably pull it out and take a closer look. Was hoping it was an injury and just mucus covered, they can be a little flighty when you don't have enough of them. This one was in a group of 3 for a while, and I was trying to get more, but availability has been slower than I had hoped. Also, the smallest of the regulars has a "chip on his shoulder", had it since I received it, not sure if it's a growth or an old wound. At first, I thought it might be a fungus, but it looks different, lighter and doesn't seem slimy. It seems to only grow as the fish does, and doesn't impair it at all.

These guys are in with a 12" Bichir, and I'm starting to think that in the future, anything smaller than what I got this time is going to have to go into a grow-out tank. I was thinking that maybe the Bichir jumped at one of the feeders and startled the bigger silver dollar, and it got a wound on the side. Bichir works himself down into the substrate for camouflage, then pounces on feeders.

I haven't heard from the seller yet, but last communication sounded like they would send me some spotted silver dollars if he thought the pickers grabbed the wrong fish. We'll see how my new phone handles pictures, if there's not a great improvement, I'll have to net trap them against the front of the tank to get good pictures of each. I really appreciate all the info, I really had no idea on sexing them, and not really interested in breeding anything at this time, but it's always nice to know what you've got.