Can Anyone Explain This Apparent Freak Of Nature?

[espokane]

I was away with my son at summer camp and received an excited phone call from my other son that "the zebra danio is pregnant." My first thought was that this was quite impossible, since we have only a single danio which has been in the tank for at least six months (I know, they like schools but we just hadn't gotten around to it yet).

His description was that the belly was bulging and looked very pregnant. My wife confirmed this. We have had mollies give birth before, and the appearance was similar. My son wanted to separate the danio into a net-cage fry isolation area, and I said sure, go ahead while thinking the danio must have a tumor or something.

The next day, to my utter surprise, my wife called to say that the danio had died and there were now 20+ fry in the isolation area!! This was quite a shock since I am absolutely certain that the fish could not have mated with another danio, as we have no other danio and never have had one and we've had it far too long for it to have come pregnant from the pet store. I have since re-checked online to make sure the danio was really a danio, and I am 100% certain going on appearance. [Looked just like this] The dead fish appeared normal, without the distended belly.

The other fish in the tank include:
Molly [Poecilia sphenops] - multiple varieties
Platy [Xiphophorus maculatus] - multiple varieties
Silver Hatchet Fish [Gasteropelecus sternicla]
Glass Fish [Chanda ranga]
Neon Tetra [Paracheirodon innesi]
Plecostomus [Hypostomus plecostomus]
Chinese algae eater [Gyrinocheilus aymonieri]
African Dwarf Frog [Hymenochirus boettgeri]

So, my wife went to the pet store to get fry food and the mystery deepened when they learned that danio are egg-layers! Unfortunately she disposed of the dead danio - I really would have liked to take a look at it post mortem.

Can anyone help us understand how our single zebra danio gave live birth?

The fry appear mostly transparent, about 1 cm in length, and quite healthy so far. They have some color toward the head, which is somewhat varied from fish to fish, but all have transparent body/tail. I was half expecting them to look like little tiny aliens...

I am greatly looking forward to any answers you can provide. I have a degree in biology, so I am particularly interested in any theories or similar experiences readers of this forum can offer.

Regards,
Eric in Spokane

 

[helterskelter]

It's impossible for a danio to give birth, as u correctly say they are egg scatters and produce 100's of eggs which are fertilised in the water.

You say u got platies and mollies, and due the size of the fry they will be molly fry for sure, platy are usualy 4-6mm in size.

Let's just make this clear, you (well wife) trapped a danio and next day in the trap was large 1cm fry, these was not found in the tanks and then moved?

If so then someone is playing a prank!!!!1

 

[MHunt]

Interesting. Is it beyond the realms of possibility that a male livebearer could have tried to mate with the danio, and the eggs grew inside. With no mechanism for live birth the danio died, and these are some bizzare hybrid? If the fry survive could you get some pictures up?

 

[helterskelter]

For one seconed if you think a danio was inpregnated by a livebearer and viable fry was produced, the eggs are tiny, and danio fry are about 2mm and see through, the first stage in devlopment is the larval stage where they swin up onto plants and rocks in open water to absorb the jolk sac for 1-2 day's.........

As a danio has no precess to absorbe the sperm from a male and like MHunt said they have no way to give birth

How ever This is impossible

Good prank though

 

[espokane]

This is absolutely not a prank. Why would I join a fish forum just to make some elaborate trick on people I don't even know? I am as confounded as anyone here. I have reviewed the events carefully with my wife, and they are as follows:

1. Danio appeared to have a huge bulging belly
2. Danio was separated into a rectangular box with netted walls and open top (made for live-bearers)
3. The next morning, the danio was dead at the bottom of the netted box and it was filled with many little 1 cm fish

I considered the possibility that one of the mollies gave birth coincidentally and the fry somehow got into the netted box, but there are problems with that theory. Why was the dead danio back to regular size? If the fry can get through a hole INTO the box, why are none getting back OUT again? Also, the box is at the top of the tank and the molly fry we once had before we had this separation area all swam down to the corners, not up.

I also considered whether my wife and son might be playing a prank on ME as I think someone suggested. My wife isn't the type to do that, besides, it isn't really very funny and I give her more credit than that! Even if it were a joke, she would have come clean long ago and not tried to fool our elementary age kids this long, so that theory can be dismissed.

I will try to get photos today. Many of the fry not only survived, they are healthy and eating well. Unfortunately I'm not sure what to do with them. I need to do a water change, but doing so will be interesting as the water level drops. Someone will probably have to hold the net box at water level so as to keep the fry inside and in water.

Actually, perhaps setting up a 10 gal aquarium for the sole purpose of keeping the fry alive long enough for them to grow into identifiable adult fish is what I should do, just so I can see what the heck they are. Pictures forthcoming if I can get them!

Regards,
Eric

PS: The mollies we had that gave birth previously (two occasions) happened to both be black. The fry were also black. We currently a mottled ("dalmation") molly, a yellow/orange "balloon" molly, and a white molly, as well as a red wag platy and a mickey mouse platy. Would any of these have fry that do not appear to have the same coloring?

PSS: There must be a term for this "net box" thing, but I can't remember what it is. A birthing box? A fry tank? It's not really a quarantine, since water is shared with the larger aquarium...

 

[Lateral Line]

I believe the others were suggesting that you might have been the victim of a prank, not us.

There is no way a danio has given birth to live young. The genetic makeup of Cyprinids would make it quite impossible for a male Poecilid to create viable offspring. Interspecific, or rarely intergeneric hybrids are possible, but from such distantly removed species, well, no.

Re: PS

The reason people who keep livebearers keep only one type per tank is that they are renown producers of worthless "mongrels". These can share some or none of the desirable characteristics of their parents. Many "desirable" traits are genetically recessive. Females can produce several "litters" from the same coupling, so after a female livebearer has been exposed to males of any related species, anything she later produces will be suspect.

Re: PPS

The net contraption you inquire about is often called a "breeding trap", and is used with livebearers. With egg scatterers it would be useless of course as the male is needed to fertilise the eggs as they are expelled.

The simple thing would be to grow the fry on and see which of your livebearers have produce them.

 

[helterskelter]

LOL What I'm trying to say is that you have been fooled well and truly

Danio eggs are tiny, and even in the slightest if one did give birth the fry would be 1-2mm and clear they physically can be no larger as they live off the yolk sac, even in common livebearers.

If you rearly have a degree in biology then this would surely make scene and see what's been done to your self.

Must say though i hate to read long topic's i get borad and move on after a couple of lines but this is very intresting and one to read in full.

 

[espokane]

To Lateral Line: Very informative, thank you.
To helterskelter: If I understand your post correctly, you still think someone is attempting to fool me. I just confirmed with my wife that there's no pranking involved, so that's not it but thanks for the reply. And yes, I really have a degree in biology.

I'm still amazed with the apparent coincidences. Considering the breeding tank isolation, death of danio, and appearance of fry within the breeding tank, it sure seems like the fry came from the danio. The science major within me knows it has to be some other explanation, but what a crazy set of circumstances. I'm sure you can understand why this is confounding, considering the facts at hand. Anyway, please see photos below - I did my best. If anyone can ID, that would be great!

Related questions or posts that I would have placed here had the events unfolded differently:

Why did my danio die? I had a healthy danio for a few months. A few days ago, we noticed it had a greatly distended belly. The next morning, it was dead and back to normal size. What happened?

How can I keep these fry to maturity? I have about 20 fry of unknown species, most likely Molly or Platy. They are in a breeding trap within a 20 gallon tank. Any tips?

And also, A VIDEO

Thanks again,
Eric

 

[-germ-]

Maybe the danio died of dropsy and it just happened to coincide with a livebirth?
Edited for stupidity...

 

[helterskelter]

Their could be many reason for the death, dropsey as stated alread, and other general problems, female danios to swell up quite large when their with eggs, so that may be why she was large.

But with out water quality it's hard to rule that out.

To stop problems just keep doing weekly water changes.

As for the fry they look like typical molly fry but look very large,

 

[severum boy]

The fry look like the livebearer fry I have had, in particular Mollys. They are NOT Danio fry.They would still have yolk sacks and not be moving around much at all.

 

[Tommo]

You are certain it was a danio? Those are livebearer fry all right

 

[MHunt]

Woah, how old are the fry in those pictures, they're really well developed. My cory fry only look like that after three weeks!

I'd say more molly than platy, but having never seen the fry of either i couldn't be sure.

The death of the danio is probably an unfortunate coincidence. I think this whole confusion is down to someone putting a molly (or platy) that was giving birth in the breeding net, and not owning up to it!

 

[espokane]

Well, no Molly was ever in the breeding trap at any time, only the Danio. Yes, I am 100% positive it was a Zebra Danio. However, the trap was adjusted and the string tightened after the fry were discovered. I suspect that one of the mollies happened to give birth at the same time the danio died (although I still don't quite understand why it was huge and then back to normal when dead.) The fry then found their way into the breeding trap on their own. I suppose any that didn't do that became part of the food chain. The breeding trap adjustment explains why the fry have since remained inside - the adjustment must have closed the hole (I haven't been able to inspect it while in use).

I should have stuck a ruler in the water for the photos. If you're familiar with that common breeding trap, you can estimate the size. They are larger than I remember the new fry from our black molly. Maybe they had been born and were hiding out until the breeding trap was placed, then they somehow knew what it was for...

How's that for an incredible set of coincidences?

Thanks for all the helpful feedback.

My only regret is telling my six-year old son that they aren't "Baby Daniels" (as he calls them) after all, but Baby Mollies instead!

I'll check back if I can manage to keep the fry alive. They're already seeming to prefer flake food which has been ground into very small bits over the "fry food" which is a slow-sinking powder type of meal. Might need to make a hasty 7 or 10 gallon aquarium setup.

Eric

 

[K.J.]

Defo livebearers, could you tell us exactly what the danio looks like?