PlanetCatfish.com

In the same tank I keep aeneus, habrosus, similis and CW008. About 2 months ago, the aeneus were spawning profusely on the front glass of the tank.

The last 2 weeks I have been coming home to smaller eggs that were laid on an Amazon sword leaf right in front of the outlet.

I expected it to be a different species, also because they invariably hatched after 2 days instead of 3 and are half the size of the aeneus fry.

However, today I noticed spawning behaviour from some of the smaller aeneus but no eggs on the glass. And then, again a large group of smaller eggs on the leaf!

So, my question is: can the same species have different egg sizes and different places for depositing their eggs? Or are these indeed 2 different species spawning?

Certainly they can use different places for depositing eggs, but different egg sizes doesn't seem right to me.

I've gotten different sized eggs from the same parents before, but not an entire batch of eggs notably smaller than others. Usually it's just some eggs within a clutch that are smaller than other eggs in the same clutch, and in those cases the smaller eggs don't develop as far as I can tell. I've always attributed the smaller eggs to being incompletely filled with yolk, but that's just a guess.

Generally speaking, it's certainly known to occur that in some animals (I'm thinking frogs, but fish might too), very young but sexually mature females can produce smaller eggs than older, larger females. But the differences are subtle, not extending beyond the documented range of normal oocyte variation within the species. If this did occur in corys for the same reason I mentioned here, considering how small cory eggs are to begin with, they might not be visibly different to the eye if this did occur.

This all assumes the eggs are being produced by normal healthy females. There are plenty of things that can be wrong with females (nutrition, hormones, stress, etc.) that might result in the production of abnormally small eggs. But again, as I have seen with some of my eggs, you wouldn't expect the smaller eggs to develop as well as regular sized eggs.

Cheers,
Eric

Thanks for the answers, especially Eric!
I know now that it should be a different species then as all eggs have been hatching and it is already the 3rd batch now with these smaller eggs.

Fry also seem to behave differently as they seem to be 'grazing' more on the sides of the tub I am using to feed them during the first weeks.

So, now the question is: which species is it?! Habrosus, similis or CW008.
The most likely is that it is habrosus because of its size, but the funny thing is that I think I only have 1 mature adult and the rest are juveniles.... The similis are about 6 months old and the CW008 still look smallish but are all even sized.