Spontaneous ectopic head formation enables reversal of the body axis polarity in microscopic flatworms

In microscopic flatworms from the genus Stenostomum the new head and tail
structures are inserted in the pre-existing body plan during the asexual
process known as paratomy. Here, we report a spontaneously occurring
developmental error that results in the formation of worms with double
heads at opposite ends of their bodies, lacking posterior pole identity.
The first part of the dataset includes confocal images of the normal and
double head worms. The animals were stained with antibodies and phalloidin
for morphology, as well as HCR in situ for visualization of the expression
of head and tail molecular markers. We also demonstrate that the piece of
the worm with ectopic head can survive, regenerate the tail on its
previously anterior pole and resume asexual reproduction. The second part
of the dataset includes microphotographs of two regeneration time series
of fragments with an ectopic head - one that retained the ectopic head
after amputation and one that resorbed it.