Sex in dictyostelia

Abstract

Dictyostelid social amoebae possess both sexual and parasexual cycles. In the former, diploid zygotes attract surrounding haploids and then cannibalise them, forming large immobile structures known as macrocysts. In the parasexual cycle, amoebae of the same sex fuse to form diploids that can continue to grow and multiply. Species with more than two sexes (or mating types) are not unusual among dictyostelia, and recently the genetic basis for sex determination was described in the model species Dictyostelium discoideum. Macrocysts have so far only been observed in a minority of the known species, and their ecological context and significance is still not understood. Important questions regarding altruism, genetics and the basic cell biology of both the sexual and parasexual cycles remain to be addressed experimentally, so there remains tremendous scope for future research.