Sea no­mads’ su­per­sized spleens

Action Asia - - NEWS & VIEWS -

FOR MORE THAN 1,000 YEARS, the Ba­jau have lived on boats around Malaysia, the Philip­pines and In­done­sia, spend­ing more than 60% of their eight-hour work days un­der­wa­ter, spear­ing fish and oc­to­pus, and gath­er­ing crus­taceans and sea cu­cum­bers at depths greater than 70m. Equipped with only a wooden mask, the Ba­jau are said to ex­pe­ri­ence the most ex­treme low-oxy­gen sit­u­a­tions any hu­mans en­counter. Now re s e arc hers at t he Univer­sit y of Copen­hagen (UCPH) and UC Berke­ley have found that the Ba­jau have an adap­ta­tion to help them in this dan­ger­ous work: un­usu­ally large spleens. Ul­tra­sound scans re­vealed that the spleens of Ba­jau were 50% larger than those of the neigh­bour­ing Saluan peo­ple, mostly farm­ers, who do not dive. This means they could mo­bilise up to 10% more oxy­genated, red blood cells when sub­merged. The fact they found no dif­fer­ence in spleen size be­tween Ba­jau who dived and those who didn’t, sug­gests it is some­thing they are born with rather than some­thing they af­fect dur­ing their lives as divers. “While it is un­healthy to have high con­cen­tra­tions of red blood cells all the time, it is re­ally good for you if you have high RBCS when you re­ally need them,” said Nielsen Willer­slev, se­nior au­thor of the pa­per. “They have in­creased the stor­age ca­pac­ity in the spleen for when they need it, but they don’t have any neg­a­tive ef­fects of con­stantly hav­ing too high red blood cells.” Fif ty-nine Ba­jau and 34 Salu­ans were sur­veyed for the pa­per which also re­vealed data from saliva swabs showed the Ba­jau had dif­fer­ences in 25 genes. Re­search to con­nect these ge­netic vari­a­tions with spleen size con­tin­ues.

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