The guts of sea spiders move oxygen throughout their body and up and down their long, slender legs. Photo by Timothy R. Dwyer/ARCUS
July 10 (UPI) -- New research shows sea spiders use a unique mechanism to move oxygen through out their bodies. Most animals use their heart to move oxygen. Sea spiders use their guts.
"Unlike us, with our centrally located guts that are all confined to a single body cavity, the guts of sea spiders branch multiple times and sections of gut tube go down to the end of every leg," H. Arthur Woods, researcher at the University of Montana, Missoula, said in a news release. "In effect, sea spiders guts are 'space-filling' and ubiquitous in their bodies in the same way that our circulatory systems are space-filling and ubiquitous."
Sea spiders use gut peristalsis to move oxygen through their guts. The mechanism, the involuntary constriction and relaxation of gut muscles, is the same used by the guts of most animals to move matter through the digestive system.
The peristaltic waves generated by the sea spider's rapidly contracting gut muscles are much stronger than what would be sufficient for the movement of digested matter alone.
Sea spiders absorb oxygen directly through their cuticles, or hairs, that line their long, slender legs. The oxygen is then moved through the body by the gut's extra strong peristaltic waves.
The latest research -- published this week in the journal Current Biology -- is part of a broader effort to understand "polar gigantism" impacts various biological mechanisms. Species adapted to polar habitats tend to boast larger bodies their relative living closer to the equator.
Woods and his colleagues were curious to find out how animals like sea spiders move oxygen throughout such a large body.
Because the bodies of sea spiders are so skinny, it is easy to see inside with a microscope. Researchers noticed the hearts of sea spiders weren't moving blood beyond the center of the body.
"My 'aha!' moment was to consider that maybe all that sloshing of blood and guts was not about digestion but instead about moving respiratory gases around," Woods said.
Researchers used biomarkers and imaging to trace the movement of blood. They also manipulated spiders' gut peristalsis and measured the impact on the movement of oxygen.
Their findings confirmed their hypothesis that the spiders use their guts to transport oxygen. Researchers suggest analysis of arthropods with similarly complex gut systems could reveal unique respiratory mechanisms.
