Mystery offspring, different species from parent??!?

[Rob2718]

We have started breeding several of our egg laying fish. Each type of fish has its own tank and I either siphon out the eggs to an egg tray until they hatch, or remove the adults and see what hatches in the next few days. Once the fry are big enough they all go together into a small fry grow out tank, and then when they get big enough to eat the newcomers, they go into a big fry grow out tank.

I now have three Melanotaenia trifasciata (at least they look very much like it) that I raised from eggs, now about 1+ inches long and starting to get some nice colors. Funny thing is, we don't have any and have never had any adults of this species. We have been breeding Black Emporer tetras, Blue Eye Gertrudae rainbowfish, White Cloud mountain minnows, Emerald tetras, CPDs, and Cory cats. So the parents are one of these types of fish. I thought they were baby Black Emporer tetras at first, as I thought those were the parents, but it could be any of them.

Is this even possible? The only thing I can think of is some fish (Black Emporer perhaps) were interbred with Melanotaenia trifasciata and some of the offspring looked like black emporers but were half Melanotaenia trifasciata, and so when I bred them, some of the offspring were fully Melanotaenia trifasciata. Have you ever heard of this happening before? 

[Guppysnail]

Is there any chance you added new plants that may have had eggs on them? 

[Odd Duck]

On 8/28/2023 at 11:04 PM, Rob2718 said:

We have started breeding several of our egg laying fish. Each type of fish has its own tank and I either siphon out the eggs to an egg tray until they hatch, or remove the adults and see what hatches in the next few days. Once the fry are big enough they all go together into a small fry grow out tank, and then when they get big enough to eat the newcomers, they go into a big fry grow out tank.

I now have three Melanotaenia trifasciata (at least they look very much like it) that I raised from eggs, now about 1+ inches long and starting to get some nice colors. Funny thing is, we don't have any and have never had any adults of this species. We have been breeding Black Emporer tetras, Blue Eye Gertrudae rainbowfish, White Cloud mountain minnows, Emerald tetras, CPDs, and Cory cats. So the parents are one of these types of fish. I thought they were baby Black Emporer tetras at first, as I thought those were the parents, but it could be any of them.

Is this even possible? The only thing I can think of is some fish (Black Emporer perhaps) were interbred with Melanotaenia trifasciata and some of the offspring looked like black emporers but were half Melanotaenia trifasciata, and so when I bred them, some of the offspring were fully Melanotaenia trifasciata. Have you ever heard of this happening before? 

I won’t say it’s impossible because there have been some very unexpected hybrids formed, but it is incredibly unlikely that tetras would cross with rainbows.  Melanotaenia trifasciatas are phylum Chordata (same as us and all other animals that have a spinal cord), class Actinopterygii, order Atheriniformes, family Melanotaeniidae.  Black Emperor tetras [Nematobrycon palmeri var. "Amphiloxus Black] are phylum Chordata, class Actinopterygii, [here’s where the difference starts] order Characiformes, family Characidae.  Hybrids within genus are relatively common (across species), within family but different genus are much less common but still fairly well documented, within order but across family are extremely rare.

Hybrids that are produced across species are often sterile, across genus nearly always sterile, and across families I would expect to be sterile 99.99% of the time or more, across orders the odds of happening are so incredibly low.  The odds of a hybrid occurring across orders like Atheriniformes and Characiformes is likely vanishingly small and almost guaranteed to be sterile if it actually occurred.  It would be like a hawk mating with a canary.

I would expect some mystery eggs coming in on plants or hardscape, or in water from the fish store, to be a far more likely source of rainbows being produced from a species you don’t have.  Have you had any additions about 2-4 months ago for the fish to be 1” long now?

[TOtrees]

I have a few unknowns that aren't clear from your post...

Do you have any adult rainbows, other than gertrudae?

What species are the "emerald tetras", can you clarify? 

Can you post pics of the mystery babies? 

[tolstoy21]

On 8/29/2023 at 12:04 AM, Rob2718 said:

Is this even possible? The only thing I can think of is some fish (Black Emporer perhaps) were interbred with Melanotaenia trifasciata and some of the offspring looked like black emporers but were half Melanotaenia trifasciata, and so when I bred them, some of the offspring were fully Melanotaenia trifasciata. Have you ever heard of this happening before? 

I would say this is a near impossibility. 

On 8/29/2023 at 12:04 AM, Rob2718 said:

I now have three Melanotaenia trifasciata (at least they look very much like it) that I raised from eggs, now about 1+ inches long and starting to get some nice colors. Funny thing is, we don't have any and have never had any adults of this species.

Can you post pictures?

On 8/29/2023 at 5:19 AM, Guppysnail said:

Is there any chance you added new plants that may have had eggs on them? 

Yeah, that's what I would suspect.

[Rob2718]

I guess the Gertrudae would be a better bet than the Black Emperor, as they are the same order as Melanotaenia Trifasciata, but still very rare per Odd Duck's comment above. I just bred more Gertrudae fry so we'll see how those turn out. I only have one female which increases the chances of a repeat if that is what happened.

I do have Boesmani and Australian rainbowfish in another tank in another room.  The Boesmani are all males though. That tank is very aggressive about consuming eggs, but if some were attached to red root floaters that may have have been how they made it to this breeding tank.

Sorry, Emerald Rasbora, not tetra.

Not the clearest picture, but enough for Google lens to identify. From what I can tell looking directly at the fish, that identification is spot on.

When we buy plants they get rinsed and inspected, and soaked in water with alum before before being put into their new home, which is in a different room from the breeding tank. I'm having a hard time figuring out how three eggs accidentally hitchhiked their way in on some plants, and then got transferred from those plants to a different tank. They do take 7-12 days to hatch though, which gives a wider window of entry from plant purchase to breeding tank.

[tolstoy21]

On 8/30/2023 at 1:08 AM, Rob2718 said:

I do have Boesmani and Australian rainbowfish in another tank in another room.  The Boesmani are all males though. That tank is very aggressive about consuming eggs, but if some were attached to red root floaters that may have have been how they made it to this breeding tank.

As per Occam's Razor, this sound like the mostly plausible explanation. 

I have never bred nor kept rainbow fish so I am the furthest thing from an expert on the subject. But those do strike me as rainbow fish in profile and have no visible characteristics that I can see of an Emperor Tetra.  And if--let's pretend for a moment--they were some sort of rainbow/tetra hybrid, it's impossible to say what attributes we'd even see in the offspring.

[Beardedbillygoat1975]

Definitely Melanotaenia