Paired cytoskeletal patterns in an epithelium of siamese twin cells.

The epidermis of some insects is a sheet of siamese twin cells which are formed by conserving the midbody between siblings after cell division. We have found that for about 36 h after ecdysis to the 5th stage, the cells of Calpodes caterpillars contain one to five or more actin bundles. The variation in number of bundles occurs in an epithelium that is presumed to be otherwise genetically and developmentally homogeneous. The number of bundles is paired in adjacent cells (P less than 0.005, n = 617). Confocal microscopy shows midbodies between paired but not between unpaired cells. The pairing is reminiscent of the paired nucleolar patterns in these siamese twin cells (Locke, M., H. Leung, Tissue and Cell 17, 573-588 (1985)) or the mirrored patterns of stress fibers in newly divided 3T3 cells (Albrecht-Buehler, G., J. Cell Biol. 72, 595-603 (1977)). The pairing provides further evidence for the operation of transiently heritable factors as determinants for cell pattern.