These arthropods’ unusual digestive system can act like a heart and gills
Timothy Dwyer (PolarTREC 2016), Courtesy of ARCUS
NEW ORLEANS — A newfound way of delivering oxygen in animal circulatory systems depends mostly on food sloshing back and forth in the guts.
This discovery came in sea spiders, or pycnogonids, which can look like legs in search of a body. Their spookily long legs hold stretches of digestive tract, which wouldn’t fit inside the creatures’ scrap of an abdomen. Waves of contraction sweeping up and down the leggy guts cause blood outside the guts to move too, evolutionary physiologist Art Woods of the University of Montana in Missoula said January 8 at the annual meeting of the Society for Integrative and Comparative Biology. As lumpy surges of partly digested food rise and fall, blood that has picked up oxygen by diffusion whooshes to the rest of the body, Woods proposed.
“Essentially they use their legs like gills,” says Jon Harrison, an evolutionary physiologist at Arizona State University in Tempe, who was not involved in the