Jikinsa kuma na rufe shi da wata fata ta musamman, wadda take iya kare shi daga zafin rana ko kuma zafin yashi a lokacin da yake kwance. Wanna tsari na halittar raƙumi, shi ne abin da ya fito da halittar raƙumi fili, a matsayin wata cikakkiyar halitta.