swordtail aborting pregnancies?
i have 2 swordtails, one male and one female (i had another female, but she sort of wasted away and died). this female has looked very pregnant twice now, dark spot and all, then all of a sudden would look normal again. neither time have i seen any fry, and i have a decent amount of floating plants so i figured at least a few would make it. is it possible/likely that she is aborting them, or am i just not finding any of the fry?
How many days between the two times?
What length is she, in inches?
Is the tank cycled/seasoned, or new?
A lot of people mistakenly think that the gravid spot is an indicator of pregnancy but really it's the inner lining of the female's abdomen, in fact it's one of the best ways to determine the sex of month old livebearer fry. The females will start to show a gravid spot, the males will not. It's usually the first indicator, even before the male color development or the sex organ formation. Having said that, it is also the place where developing fry will be visible, mostly in the form of eyes being visible.
Based on available information, it sure sounds like she was pregnant and if she was adult sized, say, three inches or better, she would probably have had a large number of fry and some should have survived predation.
That's several "maybes" and no "definites" however. I don't believe females can deliberately abort their fry, but is triggered by something, such as poor water quality, harassment by tankmates, illness, etc. (You would probably see eggs or dead fry on the tank bottom)
Can you provide photos, and/or answers to the questions; it might shed some light.
she's probably about 2 inches long. i know that isn't really very big, but when i had swords before they were reproducing smaller than that. the tank has been up and running for a few months with mostly stable parameters (like i mentioned, the nitrates are high, but not too bad). there were a few weeks between the two times.
the reason the gravid spot seems valid is that when she gets "fat" it gets dark. when she is suddenly normal sized again it gets light again.
Ok, yea, is sounds like her gravid spot is giving you a good indication. Two inches isn't huge for a swordtail; the point I was getting at with regards to size is, a big, 4-5 inch female could crank out 60-80 fry and you should certainly see at least a few. A two inch female probably not more than 20-30 (but that's a guess). Also if she's young, the number of fry is usually smaller.
You've got a dozen fry predators in the same tank as her; I'd suggest isolating her in her own obstetrics tank for deliveries, still including floating plants as well as rooted.
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