The slagae evolved when a Morsus turpis and a tripgae mutated. It replaced the tripgae in Nuke Coast, but it didn't replace the Morsus turpis. The Morsus turpis cells works in symbiosis with the tripgae cells, working as a spine and letting the slagae grow bigger without breaking. This was favored since they are now too big to be eaten by filter feeders like the urstar. The slagae still splits in two when its big enough though; a Morsus turpis in the middle injects its enzyme into the two other Morsus turpis cells touching it, making them die in order to make the slagae split. The tripgae cells provide themselves as well as the Morsus turpis with energy through photosynthesis as before. Most of the oxygen left after the photosynthesis procedure it gives to the Morsus turpis, as well as nutrients in the water the slagae contract. This makes the symbiosis complete, making the two different cells one organism. The slagae can't control its movement, it has no need for that. It just floats in the water. To be able to avoid getting eaten without having to move the slagae now uses its ability to change color to confuse any possible enemies.