Ciliate reproduction is interesting in itself, but has broader implications for our understanding of both sex and death. They have two nucleii - a small one (micronucleus) is diploid but is not involved in transcription or day-to-day activities. The other, a much larger macronucleus, runs things day to day, but disintegrates during sexual reproduction. (Click here for more details and diagrams.)
Ciliate sexual reproduction is by conjugation - their micronuclei go through meiosis with the normal result of one surviving daughter nucleus. In the fused (conjugated) cells, haploid micronuclei are exchanged between cells, and one from each "parent" fuse, dividing along with the separation of the cells. This results in recombination and gene shuffling. The macronucleii have no involvement in this, and indeed, disintegrate during the process: new macronuclei are formed in each cell by division of the micronuclei.
While this sort of reproduction is clearly an evolutionarily early form of sex, it is also an evolutionarily early form of death. Reproduction is followed immediately by death of the controlling nucleus and loss of its genetic order. The micronuclei are equivalent to germ cells in our own bodies, reproducing seldom, and in association with organismal reproduction. The macronuclei are more nearly equivalent to the genetic components in our somatal (body) cells. The genetic content of the germ cells is passed on - by half - to the next generation. The genetic content of the soma becomes redundant after reproduction. Interestingly, before this point in evolutionary order, death was a random event only, not programmed, and not inevitable.
Ciliated protists, although small, have as many ecological niches, roles and oddities as other organisms. Paramecia bursaria, for example, becomes photosynthetic by association with engulfed photosynthetic symbiotic algae - either in their entirety or stripped down to chloroplasts alone. Others (e.g. Didinium) are fierce predators. Some, such as Coleps are scavengers. Click here for more great movies from Nikon!