We had a long discussion on tissue peeling at Reef Central and although I would love to retype all of it, I don't have the time. Let me hit the highlights.
RTN is an aquarium term. The signs of it are rapid tissue degeneration and/or tissue sloughing. Many things, including bleaching, bacteria, temperature, sedimentation, toxins, etc have all produced similar signs in corals.
This condition has been described in the wild, and it is called Shut-Down Reaction. There has been no proper histology done on wild corals with SDR. There is no known cause. The mode of infection, transmission, and overall etiology is completely unknown. It is contagious, but the descriptions of its contagion do not and in fact, cannot be bacterially mediated - the time frame makes it impossible. It is described as occurring in corals under chronic or acute stress, or with a prior history or current occurrence of White Band Disease.
It is described as "A complete spontaneous disintegration of the coral tissue…coenosaerc sloughs off in strands or blobs, leaving behind a completely denuded skeleton with not a trace of tissue left.” (Antonius 1995)
Esther Peters and I have looked samples of Acropora with "RTN" or SDR and found a coagulative necrosis with balls of tissue surrounding intact zooxanthellae. On the samples we looked at, there were no obvious pathogens present and the coral tissue immediately ahead of the necrosis looked generally healthy. I have other samples we will be looking at soon to see if the signs are consistent between and within species.
The big point here is the huge lack of information on this condition. There is no really valid work on this condition yet, and absolutley no good reason to suspect that bacteria are causative. They may play a role, they may be totally causative in some cases, totally uninvolved in others. It is just not known yet, but the one common yet vague thread seems to be stress.
