Sea nomads’ supersized spleens
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.