Photograndiscus

The photograndiscus replaced its ancestor because it is more efficient at photosynthesis. Its light-collecting disks have grown larger and turned upwards to catch more light. The entire cell has also grown slightly. Because it doesn't need to move much, its flagella have lost most of their strength and are now used solely for keeping its right side facing up. Because of its increased efficiency, it can now also live in the darker Twilight Zone, though it thrives best near the water surface.