Amictic

Amictic refers to a reproductive mode in certain organisms in which eggs develop into offspring without fertilization. The term is derived from a Greek roots meaning “without mixing,” highlighting the absence of sexual fertilization in this cycle.

In rotifers, amictic reproduction is a well-studied example. Amictic females produce diploid eggs by mitosis that develop into new diploid females without fertilization, yielding clonal offspring. This mode typically dominates under favorable environmental conditions, enabling rapid population growth without the need for mates. In many rotifer groups, environmental stability and ample resources favor the amictic cycle.

Environmental stress or changes can trigger a switch to mictic reproduction. In the mictic cycle, females produce haploid eggs that require fertilization by males to form diploid zygotes. Fertilized eggs often become dormant resting eggs capable of surviving harsh conditions and hatching when conditions improve. In some rotifer lineages, males arise from unfertilized haploid eggs, while in others, male production may be rare or absent.

The term is most commonly applied to rotifers, though it can be used more broadly to describe unfertilized or parthenogenetic reproductive modes in other organisms. Amictic reproduction provides a means of rapid population increase without mating, but it generally results in lower genetic diversity compared with sexual reproduction. In certain groups, such as bdelloid rotifers, amictic parthenogenesis is the predominant, and reportedly exclusive, mode of reproduction.