Rapid Tissue Necrosis
RTN
One of these "unknown causative organism diseases or occurrences".
Most Coral related disease and "occurrences" are caused from environmental or stress-related issues and have no known causative organism. And some that seem to have a causative organisms, have causative organism that are not typical of the reef or even marine systems.
RTN is a disease that has no known causative organism that consists of a rapidly moving white band that seems to start from the base or center of a colony and moves outward destroying the Colony's tissue as it advances. RTN can consume the Colonies tissue as a rate of an inch or more an hour. The amazing fact is that the colony remains oblivious to it's destruction.
a) in front of the band the coral remains healthy with polyps fully extended.
b) at the band the tissue detaches and dissolves.
c) behind the band the Coral's "bleached" white skeleton is all that is left.
RTN occurs most often in members of the families:
Pocilloporidae (
Pocillopora, Seriatopora, Stylophora, Madracis) and Acroporidae (
Acropora, Anacropora, Montipora, etc.).
CAUSES OF RTN
At the present time, there is no known "cause" to RTN, rather a group of possible causes. As far as Bacteria, which are endemic to the marine environment,
Vibrio sp have been implicated in a very few cases. Yet no one has demonstrated that
Vibrio is the causative factor on the whole, rather an opportunistic feeder. As Eric Borneman has stated, the fact that RTN starts and progresses from the base of the Coral cast doubt on bacteria within the water column (
Eric Borneman), for it would seem that the disease would attack the Colony from other areas rather than only at it's base.
It has also been widely circulated throughout the marine reef hobby community that aquaculture specimens have less RTN occurrences than wild harvested specimens. That may be due to the fact that aquaculture frags and colonies are well acclimated to the environment of a Home Reef Eco-System. On the other hand, traumatic harvesting, transport, overseas shipping procedure and multiple, changing holding systems of wild specimens gives rise to the delivery of an extremely stressed animal. Yet many seasoned reefers have experienced both Wild Harvested and Aquaculture specimens living large and healthy for years with no sign of problems and then BANG! RTN!
It is without doubt that RTN is born to an issue of System Parameter Stress such as
Rapid Temperature rise and fall, Prolonged High Temperatures, Poor Circulation, Low calcium and/or Alkalinity Values and other "Coral Shockers" such secondary metabolites. RTN can also be born by the simple introduction of a specimen to a system
. These facts point to the weakening of the Coral and then an opportunistic bacteria infection leading to RTN... yet many have tried an application of an strong antibiotic without success excepting rare occurrences.
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I did not write this just copied from the web
If possible post a picture than I'm sure more people on the board would be able to help.
