Olivia Judson, via her column in The New York Times, wrote this column which documents the abnormal sexual habits of the Ciliate, a single cellular protozoan.
The part that stood out most to me was the following passage:
_Each ciliate has something called a micronucleus; this contains two complete versions of its genome. During sex, the micronucleus divides in such a way that each individual keeps one version of its genome for itself; it then gives an exact copy of this version to its partner. Afterwards, each individual fuses the two genomes (the one it kept and the one it got) to make a new micronucleus.
This has three odd consequences. The first is that, by the end of sex, the two individuals have become genetically identical. Its as if you and your mate began coitus as yourselves and finished as identical twins. _
How romantic is that?! Two individuals spend their lives looking for one another, dating, going to the movies, dancing, and other forms of protozoan courting. When one Ciliate finds its perfect match, it's soul mate, they get together and, quite literally, become one another. They combine their DNA and both leave as the same organism.
This odd romance reminds me of Aristophanes' tale of the cartwheel people from Plato's Symposium. In his myth, humans began as double beings, entities consisting of a man and a woman as one giant body. The gods, who became jealous of their love, separated these beings into what we now know as men and women. So, for every person, there is a former part of a greater being. Only when one finds their mythological partner will their bodies recombine and they will be whole again.