Amazing stuff! Wish you could split your body in half sometimes? Maybe this is more than a curiosity!
"... Stenostomum brevipharyngium? This microscopic flatworm reproduces asexually by splitting its body in half, with each new worm regenerating either a new head or a new tail. But this process, known as parotomy, doesn’t always go as planned—sometimes resulting in offspring with heads at both ends.
Surprisingly, these bizarre-looking critters don’t seem to mind. When scientists looked more closely at the worms’ brains, they found that, while some structures were a bit topsy-turvy, they didn’t appear to be malformed—suggesting that the erroneously grown heads are fully functional. The defect also isn’t heritable, so a double-headed individual can go splitsies to produce perfectly normal offspring. Chopping the mutant worms up into pieces revealed that a fragment with a misplaced head can even grow a new tail at what was once its front end, creating a healthy animal with its head and tail positions permanently swapped. ..."
From the abstract:
"In most of the animals, the antero-posterior axis is specified during early embryogenesis. However, in the organisms that undergo somatic asexual reproduction, constant re-establishment of the body axis occurs during each asexual act in the context of the fully formed adult body.
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. In the set of experiments, we show that the double-head phenotype is not heritable on the organismal level.
Worms originating from the sectioning or fission of the double-head animals give rise to the healthy populations that do not display the erroneous asexual development.
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.
Effectively, such regeneration allows stable reversal of the body axis polarity without impairment of the survival or reproductive abilities of the animal, an exceptionally rare phenomenon among bilaterians."
Spontaneous ectopic head formation enables reversal of the body axis polarity in microscopic flatworms (open access)
Fig. 1 Morphological comparison of the wild-type asexual and double-head Stenostomum brevipharyngium
Fig. 4 Reversal of the body axis polarity in the regenerating middle zooid of the double-head worms.
No comments:
Post a Comment