A curious abnormally developed embryo of the pill millipede Glomeris marginata (Villers, 1789)

This paper reports on an abnormally developed embryo (ADE) of the common pill millipede Glomeris marginata. This ADE represents a modified case of Duplicitas posterior, in which two posterior ends are present, but only one anterior end. While the major posterior germ band of the embryo appears almost normally developed, the minor posterior germ band is heavily malformed, has no clear correlation to the single head, little or no ventral tissue, and a minute amount of yolk. The anterior end of the minor germ band is fused to the ventral side of the major germ band between the first and second trunk segment. At least one appendage of the second trunk segment appears to be shared by the two germ bands. Morphology and position of the minor germ band suggest that the ADE may be the result of an incorrectly established single cumulus [the later posterior segment addition zone (SAZ)]. This differs from earlier reports on Duplicitas posterior type ADEs in Glomeris marginata that are likely the result of the early formation of two separate cumuli.