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Coral
Disease Identification and Information Disease Overview White band disease is characterized by complete coral tissue degradation of Caribbean acroporid corals. Two species are affected, Acropora palmata and A. cervicornis (Gladfelter, 1982). The disease exhibits a sharp demarcation between apparently healthy coral tissue and exposed coral skeleton. These signs are identical to plague, except that white band is acroporid specific (and plague has not been found on acroporids). Tissue loss usually proceeds from the base of the colony branch to the tip, although it can begin in the middle of a branch in A. cervicornis. There are two distinct disease types that differ in the pattern of tissue loss. White band Type I exhibits tissue degradation associated with a line that migrates across the coral colony. There is no obvious microbial band, although the freshly exposed coral skeleton appears band like. Tissue lysis is always associated with the moving front (which differentiates Type I from Type II. The rate of tissue loss varies from mm to cm/day (Peters et al., 1983). White band Type II also exhibits tissue degradation as a band moves across a coral colony, however in this case the moving front may, at times, have bleached zone that catches up to active tissue lysis (Ritchie and Smith, 1998) . The only way to distinguish the two types is to observe the band progression over time. No
known pathogen has been isolated (and has only been attempted for
type II), although there is a documented shift in the composition of
the population of bacteria present in the surface mucopolysaccharide
layer. The shift is
from domination by psuedomonads to domination by Vibrio
carchariae (Ritchie
and Smith, 1995). Histopathological
examination of white band Type I diseased tissue may reveal
aggregates of gram negative bacteria in affected tissue (Peters
et al., 1983)
. White band disease affects acroporids throughout the Caribbean and has decimated populations at a regional scale (Gladfelter, 1982; Peters et al. 1983; Aronson and Precht, 1997, 2001).
Infected Colony
There are two etiologies of white band disease, type I and type II. In type I, tissue destruction is associated with the moving front of the band. In type II, there is at times a bleached zone between the area of tissue degradation and the moving front. If the bleached zone is not present, type I is visually indistinguishable from type II. No pathogen has been isolated.
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