No backside, no problem for some little sea spiders.
Creatures can regenerate Almost complete parts of her lower halves — including the muscles, genitals, and anus — or do without them, researchers report Jan. 23 Proceedings of the National Academy of Sciences.
The ability to regrow body parts is not very common, but some species do manage to get rid of it. Some sea slug heads It can make a completely new body (SN: 3/8/21). Sea spiders and some other arthropods—a group of invertebrates with an exoskeleton—can regrow parts of their legs. But the researchers believed that the new legs were how strong any arthropods were, perhaps because their tough exteriors somehow prevented them from regenerating other body parts.
This photo shows a young sea spider after the last quarter of its body was amputated, including its legs and anal tubercle. The anal tubercle contains the animal’s hindgut and anus. G. Brenes et al/PNAS 2023 After the first molting, the anal tubercle and legs begin to improve, appearing as a short seed attached to a new part of the body (middle, bottom) at the hind end of the animal. G. Brenes et al/PNAS 2023 The sea spider’s anal tubercle and legs form after the animal has shed its exoskeleton for the second time. G. Brenes et al/PNAS 2023 After the third molt, the animal looks normal again. G. Brenes et al/PNAS 2023
An unfortunate accident was the first to discover the evolutionary biologist George Brenes in those sea spiders (Pycnogonum litorale) It may be able to handle more complex repairs as well. He accidentally injured one small specimen he was working on in the lab with the tweezers. “It wasn’t dead, it was moving, so I kept it,” says Brenis of the University of Vienna. after several months, The sea spider has an extra leg Instead of a scar, he and evolutionary biologist Gerhard Schultz of Humboldt-University of Berlin reported in 2016 in physics.
In the new study, most of the 19 baby spiders recovered and rebuilt lost muscles and other parts of their lower half after amputation, although the regeneration wasn’t always perfect. Some juveniles wore six or seven legs instead of eight.
None of the four adults regenerated. This may be because adults no longer shed their skin as they grow, suggesting that regeneration and moulting are linked in some way, Brenes says. Two of the baby sea spiders also didn’t regenerate at all. The animals survived with only four legs and no anus. Instead of defecating, the pair squirted waste out of their mouths.
This small sea spider has three small arms (center, bottom) which, if left untouched, will develop into the last two segments of the animal’s body, which will include two pairs of legs and its anal tubercle. G. Brenes et al/PNAS 2023 This photo shows the same sea spider, but with its developing hind body removed – the three arms from the previous photo. G. Brenes et al/PNAS 2023 After the first hair loss, there are no signs of regrowth. The animal has four legs instead of eight. G. Brenes et al/PNAS 2023 After the third molt, the animal still has only four legs and no anal tubercle. Because it does not have an anus, the animal excreted its excrement through its mouth. G. Brenes et al/PNAS 2023
The next step, Brenes says, is to see if other arthropods also regenerate more often than scientists thought, and how sea spiders do it. “I’d like to see how it works.”
