Mitotic defects associated with cytoplasmic incompatibility in Drosophila simulans

We have examined the development of embryos obtained from cytoplasmacally-incompatible crosses between different strains of Drosophila simulans to determine the effect of Wolbachia during early embryogenesis. Embryos that we observed could be placed in three categories: those with arrested development during early intravitelline mitoses, a small number that reached the syncytial blastoderm stage but failed to cellularize, and embryos whose development had been arrested shortly before hatching. Cytological analysis of the staining of microtubules, centrosomes, and chromosomes showed that characteristics commonly found in early arrested embryos were mitotic spindles that lacked centrosomes, a higher number of centrosomes than expected from the count of the nu clei, and a higher number of metaphase-like configurations. Embryos that reached later stages of development show an irregular segmental patterning, anatomical defects, and surface areas where microtubules and nuclei are highly disorganized. These findings indicate that embryos derived from cytoplasmically incompatible crosses showed arrested development at different stages. (C) 1996 Academic Press, Inc.