For Sea Spiders, It’s All in the Legs

A sea spider on a red gorgonian in Fiji.

SEA SPIDERS ARE CREATURES WITH LONG LEGS radiating from tiny central bodiesIn a class of marine arthropods called Pycnogonida, they’re found in more than 1,300 species in oceans all over the world

LOOKS SIMILAR, WORKS VERY DIFFERENTLY   The only association they have with terrestrial spiders is … a physical appearance of long legs and tiny central bodies. Other than that, they are totally unlike real spiders, or anything else, for that matter.

A sea spider, species Nymphon leptocheles, grazing on a hydroid in Norway. At the same time, a nudibranch is busy eating a bryozoan growing on its leg.

IT’S ALL IN THE LEGS   They breathe, digest and procreate through their legs. And, it develops, they pump blood through the guts in the aforementioned legs. Through their tiny hearts, not so much.

This information comes to the fore because researchers at the University of Hawaii at Manoa wanted to know why some Antarctic species grew so large – specifically, how well their hearts do in pumping blood into their legs. Sea spiders, they discovered don’t.

A GREAT READ IN ATLANTIC MAGAZINE   They published their findings in the journal Current Biology, but science writer Ed Yong had done a fascinating, layman-friendly overview of their work and of sea spiders’ overall weirdness in an article The Atlantic, “Sea Spiders Pump Blood With Their Guts, Not Their Hearts.”

Since like me you probably knew very little about sea spiders, it’s a great read!

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