Study: Sea spi­ders use guts to pump oxy­gen

China Daily (Hong Kong) - - WORLD -

WASHINGTON — Most an­i­mals de­pend on a beat­ing heart to pump blood and oxy­gen, but sea spi­ders do this mostly with their un­usual guts, ac­cord­ing to a new study pub­lished on Mon­day.

“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,” lead au­thor H. Arthur Woods of the Univer­sity of Mon­tana, Mis­soula, said in a state­ment.

“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.”

The study, pub­lished in the jour­nal Cur­rent Bi­ol­ogy, found that sea spi­ders, which take in oxy­gen di­rectly through their cu­ti­cles, use peri­stal­sis to move flu­ids.

The hu­man gut also uses peri­stal­sis — waves of in­vol­un­tary con­stric­tion and re­lax­ation of mus­cles — to mix gut contents and move them along.

Woods and col­leagues made the dis­cov­ery af­ter an Antarc­tic mis­sion to ex­plore a 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.

The trend raised a lot of in­trigu­ing ques­tions about how the po­lar species man­age ba­sic life pro­cesses, in­clud­ing how to get enough oxy­gen into their bod­ies.

“My ‘aha!’ mo­ment was to con­sider that maybe all that slosh­ing of blood and guts was not about di­ges­tion but in­stead about mov­ing res­pi­ra­tory gases around,” he said.

It’s not clear whether the sea spi­ders’ space-fill­ing guts first arose for purely di­ges­tive func­tions and the res­pi­ra­tory ben­e­fits came later or vice versa, the study said.

“Res­pi­ra­tory gut peri­stal­sis may be more wide­spread than pre­vi­ously rec­og­nized,” the re­searchers wrote in the pa­per.

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