Spiders are horror movie stars for a reason, and while there are several in your backyard that could have crawled out of Arachnophobia, this one takes it straight to Alien level.
Sea spiders (aka pantopoda or pycnogonids) aren’t arachnids, but these eerie marine arthropods still have that ominous eight-legged figure that has terrorized so many of us from countless basements and dungeons onscreen. They look like a lab experiment that attempted to splice the DNA of Jack Skellington with a facehugger went far beyond the petri dish. As if that wasn’t enough nightmare fodder, you may not want to read the new research published in Current Biology at night. Scientists have now discovered that they get blood and oxygen rushing through their legs to creep around underwater by pumping not their hearts but their guts.
Nothing about the sea spider’s digestion process is remotely normal to begin with (but you expected that). They would put Hannibal to shame with their dining habits, which involve impaling unfortunate victims like sponges and sea anemones with a murder weapon of a proboscis with which they suck up chunks of flesh marinated in digestive juices. With abdomens grossly disproportionate to their legs, these things need to release their innards to avoid an internal explosion when feasting. Enter the spiders’ even more grotesque method of branching out their guts to slither down through their spindly legs whenever they have cravings.
These multipurpose viscera also act as a sort of steampunk-ish pumping device that sends oxygen-saturated blood, or hemolymph, coursing through the creature’s body in a method that was previously unknown to science. The team whose stomachs were strong enough to make this discovery observed that sea spiders compensate for their weak hearts by powerfully contracting their intestines to siphon the hemolymph, which exists in a glob instead of blood vessels, back and forth throughout their skeletal frames (enter splorching and splooshing sound effects). Welcome to the bizarre world of respiratory gut peristalsis.
“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,” said researcher and lead author H. Arthur Woods of the Division of Biological Sciences at the University of Montana, Missoula.
After reading that, you shouldn’t expect anything less odd about the sea spider’s respiratory system, which may explain how they evolved and continue to survive. Without the advantage of gills, they breathe by diffusion, passively sucking in oxygen from the water through their porous exoskeletons. Now scientists are wondering whether this kind of internal plumbing, which has probably powered these creepy-crawlies for hundreds of millions of years, exists in other kinds of arthopods.
Get ready for the next creature feature sensation.