Flavuslime

The flavuslime replaced it's ancestor due to it's increased energy efficiency. The flavuslime moves considerably less than it's ancestor, instead it tends to stay on the same rock for long periods of time. While it is capable of moving through the water, it is slower than it's ancestor and thus more vulnerable. Since they tend to stay on the same rock, the rocks develop a slippery slime over them. The flavuslime's 'wing-like' structures further evolved from their flagellum and more efficient at holding them in place. This allows them to survive swifter waters, only losing grip to their rocks in rapids. They still possess an eyespot that lets them know where the light is, but since they don't move as often it's not used as much causing it to degrade. Their lack of movement has allowed them to be more energy efficient letting them reproduce almost twice as often as their ancestors. They also live marginally longer.