their little "cloaks" are actually part of their body, another remnant of their botanical heritage! what, do you think they found cloth in the abyss? the mantles are kind of leaflike in structure, with "veins" running through them. the ragged appearance is perfectly natural, it's actually a fairly resilient material, though of course it can still be torn if one tries hard enough. the mantle can repair itself given time and of course adequate food, or regrow entirely if necessary-- a growing vessel will inevitably shed their mantle several times during the course of their molts