I can see this is an older thread, but it caught my eye because I have some MTS snails that are much, much larger than the usual ones. They have no stripes on them, the shell is a dull olive shade. They reproduce more slowly than the small striped ones, have a much larger foot in comparison to the striped ones. I'm trying to get a population of them going, and have been asking here and there if anyone knows of other species or types of MTS. The largest one I've had so far has a foot a bit larger than a dime, and the thick end of the shell is more than one half inch in diameter. The shells tend to be darker in colour at the sharp end.
I quite like these guys. I've been calling mine Olives, because I don't know their proper name. Hoping to get enough numbers so I can sell some later on.
I also have had Yellow and Orange Poso Rabbits. Not in the same tank though. The yellows bred fairly quickly, one baby at a time, but I got 3 or 4 babies from one pair in two months time. They ate my American swords to shreds and uprooted most of the plants with their constant digging to the bottom of the substrate, so I eventually sold them. I liked watching them but they were just too destructive. They have very short antennae and never seem to display them, so I could not observe if antennae were different lengths in males and females.
The orange ones look like a simple colour morph, but I think they're actually a sub species or different species entirely. I wish I could find out for sure what species they all are. Orange Posos have longer antennae, for one thing, which come in two lengths only, and are usually displayed. A professor friend speculates the antennae differences are related to the sex of the snail, though I don't know if the longer antennae belong to the male or female. Females are certainly larger than males at maturity, but that's not much help before they mature. Females being larger than males appears to be common to the Tylos, they certainly have the largest baby snails of any species. The orange ones reproduce one baby at a time too, but less often than the yellow ones did. So far, they don't seem to eat plants, but currently are in bare bottom tanks, so I don't know how much they dig.