Goliathamoebas

The Goliathamoebas replaced their ancestor and spread globally, becoming dominant benthic amoebic consumers. They mainly consume sessile, benthic, and otherwise slow-moving microbes, though they may occasionally try to catch faster motile cells and even the occasional meiofauna. At a glance they’re pretty similar to their ancestor...at least, until one takes a look at the nucleus.

The nucleus of Goliathamoebas is, itself, big, shapeless, and amoebic. It is filled with thousands of redundant copies of their genome, and contains a second nucleus-like organelle in the center dedicated to producing micronuclei. During cell division, the micronuclei are ejected from the cell to be picked up by other Goliathamoebas. To avoid their genome becoming bloated over time, no DNA in the main nucleus is replicated during cell division, daughter cells instead having roughly half the DNA of their parent until they pick up micronuclei to expand their genome again. This genetic recombination method has resulted in a genetically more healthy population.

There are many, many species of Goliathamoeba. They can live anywhere that has water and oxygen, though they can and do venture into anaerobic conditions such as decaying flora for brief periods of time to feed. They are typically rare or absent in hot deserts, their nature making it difficult to evolve to completely resist desiccation, though they can still be found in the local water table and therefore oases. Freshwater species use vacuoles to remove excess water, and species in colder habitats have slower metabolisms and can slow down even further in the winter. Like their ancestor, they have no color; the color depicted is for visual clarity.