New organs for the isopod spider
he isopod spider Pycnogonum litorale has extraordinary regenerative abilities: It can not only regenerate legs, but also complete torso segments with internal organs such as muscles, intestines and reproductive organs at the rear end of the body. This was discovered by a group of evolutionary biologists from the Universities of Vienna, Greifswald and Berlin. The researchers, led by Viennese zoologist Georg Brenneis, suspect that this regenerative potential may have been an original feature of arthropods.
The most species-rich group of animals on our planet, the arthropods, i.e. insects, crustaceans and arachnids, have been endowed by nature with a phenomenal property. Many of their representatives are able to regenerate their limbs. However, parts of the main body axis, i.e. the trunk, do not have this regenerative ability.
However, there is one representative that has exactly this potential. In a new study, evolutionary biologist Georg Brenneis and his colleagues investigated the regenerative capacity of the sea-dwelling eight-legged isopod spider Pycnogonum litorale. Over several months, the biologists documented the different developmental stages of 23 animals from which various pairs of legs and posterior body parts had been removed. They analyzed the subsequent development of the external shape and internal organs using fluorescence microscopy and X-ray micro-computed tomography and visualized them using digital 3D reconstruction.
Adult animal after complete regeneration of the third right leg and the entire last trunk segment with the fourth pair of legs and the end of the body. Image: Georg Brenneis
Surprisingly, the animals showed an impressively high survival rate, even after serious injuries. Almost all of the individuals that had not yet fully matured showed complete or almost complete regeneration of the missing body parts. “This did not only concern the formation of new limbs,” says Georg Brenneis. “Almost complete posterior trunk segments with musculature and midgut tubes, the rearmost body appendage with rectum and anus, as well as missing elements of the genital organs were newly formed.”
As isopod spiders are an ancient evolutionary lineage of arthropods, the researchers believe that their regenerative potential could have been an original characteristic of arthropods. This regenerative ability may also have contributed to the success of their impressive evolutionary diversification.
The enormous regenerative abilities of some animal groups inspire physicians and biologists, not least because a better understanding of these processes is of great interest for regenerative medicine. Evolutionary researchers are still discussing why the ability to regenerate lost body structures is so pronounced in some animals, while it is only present to a limited extent in others, such as mammals, including humans.
Original publication:
Georg Brenneis, Karina Frankowski, Laura Maaß, Gerhard Scholtz.
The sea spider Pycnogonum litorale overturns the paradigm of the absence of axial regeneration in molting animals
doi.org/10.1073/pnas.2217272120
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