Cellular morphology in haploid amphibian embryos

External surfaces of haploid and diploid embryos of Bombina orientalis were examined with the scanning electron microscope to determine the possible contribution of cellular morphology to the amphibian haploid syndrome. Cellular anomalies were prevalent in all surface areas of haploid embryos. The epithelium appeared uneven due to the displacement of ciliated cells and the rounded surfaces of the non-ciliated cells. The ratio of ciliated to non-ciliated cells was altered in comparison to diploid embryos. Cells of the gill filaments and adhesive organs were abnormal in morphology, and the adhesive organs themselves were fused into a single large rudiment in haploid embryos. Uniformity of cell size was markedly reduced in head regions of haploid embryos with severe microcephaly. Haploid and diploid embryos elaborated mucoid matrices over the surface cells when removed from the fertilization envelope. It is apparent that aberrant cellular morphologies are widespread in haploid embryos, and it is likely that these defects are major contributors to the gross morphological anomalies of the haploid syndrome.