In other dinoflagellates, an analogous structure has been implicated in heterotrophic feeding and sexual recombination.

Cytological and molecular genetic studies show that bdelloids evolved from a common ancestor which lost sexual recombination (meiosis and fertilisation) about 100 million years ago.

Nuclear karyogamy and meiosis (sexual recombination) occur within the zygospores, which are thought to be long-lived and resistant to adverse conditions.

This is due to the lack of sexual recombination which would have shuffled alleles between chromosomes during meiosis.

This is followed by the formation of macrogametocytes and microgametocytes which undergo sexual recombination.

These include sexual recombination (the combining of genes from two parents) and geographic isolation (the separation of populations by a physical barrier).

This can occur by any of the following processes: transposon mediated shuffling, sexual recombination or illegitimate recombination.

The co-occurrence of the two mating types is significant due to the possibility of sexual recombination and formation of oospores, which can survive the winter.

However a recent review suggests that sexual recombination may be the rule rather than the exception in amoeboid protists in general, including the Arcellinid testate amoebae.

The two major sources of genetic variation, mutation and sexual recombination appear to be consequences of mechanisms to cope with DNA damage.