Anableps males seem to have two major interests - eating and mating. Compatible mating leads to pregnancy. Quite often the first reliable sign that a female is pregnant is a change in body shape. She loses her slender silhouette and becomes tubby in the abdominal region. Although this is very evident in the picture below, sometimes the change is not very noticeable and we have been surprised by a small number of babies from a female we didn't think was pregnant.
A pregnant female Anableps
As you will see, it's important to understand the process involved in egg fertilization and embryo development in order to provide the necessary environment for successfully raising the young. Anableps babies are sometimes aborted and each fetus always has the gut protruding out of a split-like opening in its belly. Even when the babies are born alive, the opening can still be seen with, sometimes, a bit of the gut protruding. Infection and the resulting death can easily happen if the tank water is less than ideal. I'll try to explain the little that I've been able to find out about the internals of Anableps pregnancy. Keep in mind that this is the result of reading and deducing and not from any scientific research of my own.
Healthy newborn resting on a rock
Consider follicles. The most common ones are found around hair roots. These are hair follicles like the ones I used to have on top of my head. The ovaries of animals, including female Anableps, have egg follicles which form a sack of cells around each egg. Apparently, mature eggs are not completely surrounded because impregnation by the male sperm happens within the follicle. This isn't all that unusual and for some livebearing fishes the embryo then grows and develops using only the food supply in the egg. The gestation period for such fish is fairly short, (about a month), and the babies are quite tiny at birth. It's somewhat different for Anableps. The first part of the embryo to develop is the gut and tiny vascular protruberances on the follicle wall make contact with it and allow it to take i nourishing fluids. he gestation period is much longer - approximately 3 months, and it's only at the end of that period that the rest of the body "catches up" with the development of the gut and the gut ascends into the body cavity. If all goes perfectly, babies from 1.5 to 2 inches (4-5 cm) long are born with only a slight opening or even just a line along the abdomen left as evidence of the process. It's an imperfect world ad probably due to conditions in our tanks which wouldn't be present in nature, baby Anableps are sometims born before the gut has completed its journey into the body cavity. These pictures show that if, as we did, you provide sterile conditions, the necessary development will continue to a successful conclusion even after birth. We used an antibiotic, (Chloramphenicol), frequent water changes and only live food in this case. Five out of the seven premature babies survived. Fortunately, we ad many successful births where no such strenuous measures were needed.
Note the "red" guts still partly exposed
Above are two photos of one of those babies some days later when it seemed safe to move it to a glass
bottomed bowl for for an underneath photo.
A week after birth - success!
A netful with no problems
Twelve of the 13 - a few weeks old
Babies are being born here and my camera is ready
The babies look like miniatures of their mother at birth and, even though mother Anableps often grew to 10 inches (25 cm) in our tanks, (12 inches in nature), such large babies severely limit the number possible per spawn. Although one of our large females aborted 20 fetuses, (so we assume that many are a possibility), our most successful spawn was 13 live, healthy babies. Since then we understand that a fellow hobbyist, Carl Krajniak from Michigan, had a very large female which gave birht to 16 live babies. Spawns like this don't seem like much compared to the 100 plus babies you can get from a swordtail or a Molly, but Anableps require more space and care. At one time we had 52 of them including adult, half-grown and babies from several generations and they made life very interesting and very busy in our fish room.
Once again mother "Bleps" just won't cooperate by letting me film a birth!
One of my goals has been to photograph an actual birth. I have come quite close, but not quite. Between us, Pat and I have witnessed 2 births, both of which were tail first. So far, although I've had my camera ready when births were taking place, mother Anableps simply wouldn't pose where I could get a shot. I hope to try again in the future.