While we’re all hoping for summer sunshine, you won’t catch any flatworms sunbathing, and they’ll certainly never get a tan. Like this individual, photographed over 10 days of light treatments, sunlight actually makes them lose their pigments, bleaching them a ghostly white. Only recently-discovered, this phenomenon is medically interesting, as their pigment loss involves similar mechanisms to those underlying human porphyrias. These diseases are caused by an overabundance of molecules known as porphyrins, with symptoms including skin lesions and neurological disorders such as anxiety and paralysis, depending on where the porphyrins accumulate. Porphyrins are also responsible for degrading the skin pigments of flatworms exposed to light; what’s more, starvation accelerates this pigment loss, just as dieting and other stresses can induce more severe symptoms in humans. Studying porphyrins in flatworms should help unravel the triggers and aggravating factors behind episodes of porphyria, as well as test potential drugs.
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