Obligate chimerism in male yellow crazy ants

Abstract

Multicellular organisms typically develop from a single fertilized egg and therefore consist of clonal cells. We report an extraordinary reproductive system in the yellow crazy ant. Males are chimeras of haploid cells from two divergent lineages: R and W. R cells are overrepresented in the males’ somatic tissues, whereas W cells are overrepresented in their sperm. Chimerism occurs when parental nuclei bypass syngamy and divide separately within the same egg. When syngamy takes place, the diploid offspring either develops into a queen when the oocyte is fertilized by an R sperm or into a worker when fertilized by a W sperm. This study reveals a mode of reproduction that may be associated with a conflict between lineages to preferentially enter the germ line.

A new mode of reproduction in animals Multicellular organisms typically develop from a single cell into a collection of cells that all have the same genetic material. Darras et al . discovered a deviation from this developmental hallmark in the yellow crazy ant, Anoplolepis gracilipes . Males of this species are all chimeras, a collection of haploid cells with only maternal or paternal genetic material (see the Perspective by Kronauer). These chimeras develop from fertilized eggs in which parental nuclei divide independently. Genetic analyses show that this unusual mode of reproduction is probably the result of a genetic conflict between two co-occurring lineages. —DJ

A newly discovered mode of reproduction in ants results in males being chimeras of haploid cells from two divergent lineages.