Jenynsia: One eye on each side, one-side livebearer. Most people separate them from the Anablepidae.
This is the experience of Martin Tversted from Denmark with them: There are many species distributed from Cordoba, Argentina to Southern Brazil’s highland.
J. multidentata is distributed from coastal Argentina along the coast up to Brazil. J. lineata has a very limited distribution area. It is limited to a single river system inland Uruguay. They’re 7-8 cm for the females, the males are smaller.
They do need large tanks and a big temperature variation during the year. They are excellent swimmers and do the best outside in garden ponds and they do need livefood.
They’re one-side livebearers so not all males fit all females. A good number of fish is the best to begin your breeding project. At first I only got one wild male and 6 females. Of these females, he could only mate 3. The rest, got pregnant for the first time when the new generations males came up.
They give birth outside despite 8°C. They are very coldtolerant. My fishroom keeps beetwin 8°C and 14C° in the winter and here they live with all the other fish that are outside in the garden pond in a 500 liter aquarium.
The fry grows rapidly on livefood outside (they’rte about 8-10 mm when born).
The sistemathyc about this genus isn’t still complete and new descriptions and ideas are coming out… so we can’t give you a complete overview of all the species…
You’ll get more informations trying here :
Jenynsia onca
Photographs by: Edson H. L. Pereira
http://www.mct.pucrs.br/lab/museu/ictio/english/students-lucinda.html