These are the forms of Zukia Tojiro, much like Pain he has various forms that grant him different abilities. It seems that just like Pain each body has a different special abilty. Due to the fact that Zukia is a god and he can change form at will and use his 100% Possesion Technique he can also be any gender (though he is originally male). It is also revealed in the story Origin that the swords that he weild in some of the forms help him mantain his forma and abilities.