MITOTIC DEFECTS ASSOCIATED WITH CYTOPLASMIC INCOMPATIBILITY IN DROSOPHILA-SIMULANS

We have examined the development of embryos obtained from cytoplasmaca lly-incompatible crosses between different strains of Drosophila simul ans to determine the effect of Wolbachia during early embryogenesis. E mbryos that we observed could be placed in three categories: those wit h arrested development during early intravitelline mitoses, a small nu mber that reached the syncytial blastoderm stage but failed to cellula rize, and embryos whose development had been arrested shortly before h atching. Cytological analysis of the staining of microtubules, centros omes, and chromosomes showed that characteristics commonly found in ea rly arrested embryos were mitotic spindles that lacked centrosomes, a higher number of centrosomes than expected from the count of the nu cl ei, and a higher number of metaphase-like configurations. Embryos that reached later stages of development show an irregular segmental patte rning, anatomical defects, and surface areas where microtubules and nu clei are highly disorganized. These findings indicate that embryos der ived from cytoplasmically incompatible crosses showed arrested develop ment at different stages. (C) 1996 Academic Press, Inc.