A quick review of interesting research on living things from the last month.
The guts of sea spiders pump oxygen
The heart pumps blood and oxygen throughout our bodies. But sea spiders circulate oxygen by pumping their stomachs.
The gut of these invertebrates branches and goes down each of the eight legs. Sea spiders absorb oxygen through their skins, and alternately squeeze and ease off their stomach muscles to shunt the gas-laden hemolymph (invertebrate blood) throughout their bodies. The creatures do have hearts but they beat too weakly to get the fluid moving to the extremities.
Such energetic guts probably ensure the marine invertebrates don’t get a pot belly.