Hybarder Viramoeba
Autoviramoeba mesohybarderenesis split from its ancestor by developing a radical improvement in its reproductive ability. It was already capable of transferring genetic material from one cell to another, but as it was doing this, it developed the ability to transfer organelles at the same time. This meant it no longer needed to infect another species to gain its organelles. They still needed to enter a larger cell to initiate binary fission, however, so they now "infect" their own species. A smaller cell will enter a larger cell, exchange genetic material and organelles, split it two, then leave. As they are adapted for this lifestyle, the larger, host cell can survive the smaller cells' entrance and exit. The largest cells are no longer able to reproduce on their own, as they can't find larger cells of their own species to serve as hosts, but it's still advantageous for them to host smaller cells, as it allows them to share their genes with them.
As they now handle their own organelles, Autoviramoeba mesohybarderensis have the full range of organelles that were present in their ancestor, making them equivalent to its phytoplankton stage. They have eyespots, photosynthetic organelles, and organelles that produce bioluminescence. They are attracted to light, and they glow when they sense other bright lights. This keeps them floating near the ocean surface, but it also causes them to glow in the presence of their own kind, congregating in large clouds that ripple between a dull green and a flashing purple. This allows them to find hosts/mates.