Cytoplasmic incompatibility

Definition

A unidirectional or bidirectional mating incompatibility in arthropods caused by maternally inherited intracellular bacteria (primarily Wolbachia, also Cardinium, Rickettsiella, Candidatus Mesenet longicola, and Spiroplasma) that reside in the host cytoplasm. The bacteria modify sperm during spermatogenesis such that paternal chromosomes fail to properly condense or segregate in early embryonic mitosis, leading to developmental arrest unless the same bacterial strain is present in the egg to 'rescue' the modification. This creates a reproductive barrier that can drive population divergence and is being harnessed for vector control programs.

Etymology

From Greek kytos (cell) + plasma (something formed or molded), referring to the cytoplasmic location of the causative bacteria; incompatibility denotes the reproductive failure between certain mating combinations.

Example

In the mosquito Aedes aegypti, Wolbachia strain wAlbB induces cytoplasmic incompatibility: matings between infected males and uninfected females produce embryos that die during early development, whereas infected females can successfully reproduce with any male because their eggs rescue the sperm modification. This asymmetry allows Wolbachia to spread through populations and forms the basis of release programs to suppress dengue transmission.

Synonyms

• CI

Related Terms

• Wolbachia
• Cardinium
• reproductive parasitism
• parthenogenesis induction
• male-killing
• vector control
• Symbiont
• intracellular bacterium
• unidirectional incompatibility
• bidirectional incompatibility

Usage Notes

Distinguished from other reproductive manipulations by bacteria (male-killing, parthenogenesis induction, feminization) by its specific mechanism of sperm modification and zygotic rescue. Unidirectional CI occurs when one population carries the symbiont and the other does not; bidirectional CI occurs when populations carry different, incompatible bacterial strains. The direction of incompatibility depends on which strain is present in the male versus the female, making this a powerful tool for population suppression and replacement strategies in pest and vector management.