Sentence:  Briefly, the yellow morphic males can change their status from paired to satellite and from satellite to the paired one. However, they cannot cross into the status of the red morph.... The colour <WSD>morphism</WSD> of males is proved to be irreversible after its expression at an early stage of ontogeny. 
Meaning of the word marked with <WSD> tags:  Being or having distinct variants of a plant or animal species in the same locale; polymorphism.