The nightmarish sea spider that pumps blood around its body using GUTS in its spindly legs
- Most mammals, birds and fish use a heart to pump blood around the body
- But the sea spider uses contracting guts to get oxygen around its abdomen
- These guts extend through the creature's long, gangly legs and into its body
- The legs also house the sea spider's genitalia and most of its other organs
We're used to the idea that animals use their beating hearts to pump blood around their bodies, but scientists have found one freakish exception.
The nightmarish, ocean-dwelling sea spider, which despite its name is not an arachnid, uses its guts to pump blood and oxygen around its spindly body.
The spider's guts extend through its gangly legs, where the creepy creature also keeps its genitalia.
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The nightmarish, ocean-dwelling sea spider, which despite its name is not an arachnid, uses its guts to pump blood and oxygen around its spindly body. Pictured is a giant sea spider cleaning itself atop a sponge mat in McMurdo Sound, Antarctica
Almost all of the sea spider's bodily functions are confined to its slender legs due to there being little room for organs in its tiny abdomen.
But while scientists knew that the animal used its legs for breathing, digestion, and even mating, researchers have now found they are used to pump blood and oxygen too.
'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,' said lead author Dr Art Woods of the University of Montana, Missoula.
Dr Woods became fascinated with giant sea spiders while stationed in Antarctica, where he said he found himself spending 'a lot of time just watching blood and gut flows in sea spiders.'
He noticed their hearts were beating only weakly, and moved blood only in the central portion of their bodies.
But their guts showed strong and organised waves of contractions.
'My 'aha!' moment was to consider that maybe all that sloshing of blood and guts [in sea spiders] was not about digestion but instead about moving respiratory gases around,' Dr Woods said.
The process is called peristalsis, and it happens in humans too, with waves of involuntary constriction and relaxation of muscles.
The sea spider's guts extend through the its long, gangly legs, where the creepy creature also keep its genitalia
Its purpose in people is to aid digestion, mix up the contents of the gut and move them through the intestines.
Peristaltic waves in sea spiders are far stronger than would be needed for digestion, because they must also get enough oxygen through the body.
'The findings highlight the vast evolutionary diversity of solutions to problems that all animals encounter,' Dr Woods and his team wrote in their study.
Future fossil discoveries might help scientists better understand the origins of this odd survival strategy.
Almost all of the sea spider's bodily functions are confined to its disturbingly slender legs due to there being little room for organs in its tiny abdomen. Most of the animals, including this 'marine sea spider', are smaller than a fingernail
While scientists knew that the animal used its legs for breathing, digestion, and even mating, researchers have now found they are used to pump blood and oxygen too
Sea spiders stride the ocean floor with slow, deliberate steps.
They eat by stabbing stationary animals - such as sea anemones and sponges - with their long proboscises and sucking up tissue softened by the spider's digestive juices.
Sea spiders don't have gills, and instead take oxygen in via diffusion through their porous exoskeletons.
Most species of sea spider are smaller than a fingernail, but in the cold, oxygen-rich waters around Antarctica, giant species can grow to the size of dinner plates.
Blood is pumped around the sea spider's body using a process called peristalsis, which happens in humans too, with waves of involuntary constriction and relaxation of muscles
The purpose of peristalsis in people is to aid digestion, mix up the contents of the gut and move them through the intestines, but in the sea spider it is used to pump blood and oxygen around the body
Dr Woods and his team made their discovery after an Antarctic mission to explore this phenomenon, known as 'polar gigantism.'
Scientists had long observed that polar species, including giant sea spiders, have larger bodies than their more temperate or tropical relatives.
That trend raises a lot of intriguing questions about how the polar species manage basic life processes, including how to get enough oxygen into their bodies.
They made their findings using a series of experiments and observations in 12 sea spider species involving video microscopy of tracers in the animals' blood-like hemolymph and guts.
A young visitor to the Science Museum in London studies a Sea Spider, a species researchers say move blood and oxygen through their bodies with guts that act like pumps
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