Inter-Research > DAO > v93 > n3 > p179-190  
Diseases of Aquatic Organisms

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DAO 93:179-190 (2011)  -  DOI:

Fine-structural analysis of black band disease-infected coral reveals boring cyanobacteria and novel bacteria

Aaron W. Miller1,*, Patricia Blackwelder2,3,4, Husain Al-Sayegh2,3, Laurie L. Richardson

1Department of Biological Sciences, Florida International University, Miami, Florida 33199, USA
2University of Miami Center for Advanced Microscopy (UMCAM), Miami, Florida 33124, USA
3Marine Geology and Geophysics, University of Miami, Miami, Florida 33149, USA
4Nova Southeastern University Oceanographic Center, Dania, Florida 33004, USA

ABSTRACT: Examination of coral fragments infected with black band disease (BBD) at the fine- and ultrastructural levels using scanning (SEM) and transmission electron microscopy (TEM) revealed novel features of the disease. SEM images of the skeleton from the host coral investigated (Montastraea annularis species complex) revealed extensive boring underneath the BBD mat, with cyanobacterial filaments present within some of the bore holes. Cyanobacteria were observed to penetrate into the overlying coral tissue from within the skeleton and were present throughout the mesoglea between tissue layers (coral epidermis and gastrodermis). A population of novel, as yet unidentified, small filamentous bacteria was found at the leading edge of the migrating band. This population increased in number within the band and was present within degrading coral epithelium, suggesting a role in disease etiology. In coral tissue in front of the leading edge of the band, cyanobacterial filaments were observed to be emerging from bundles of sloughed-off epidermal tissue. Degraded gastrodermis that contained actively dividing zooxanthellae was observed using both TEM and SEM. The BBD mat contained cyanobacterial filaments that were twisted, characteristic of negative-tactic responses. Some evidence of boring was found in apparently healthy control coral fragments; however, unlike in BBD-infected fragments, there were no associated cyanobacteria. These results suggest the coral skeleton as a possible source of pathogenic BBD cyanobacteria. Additionally, SEM revealed the presence of a potentially important group of small, filamentous BBD-associated bacteria yet to be identified.

KEY WORDS: Black band disease · Coral disease · Boring cyanobacteria · Ultrastructure

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Cite this article as: Miller AW, Blackwelder P, Al-Sayegh H, Richardson LL (2011) Fine-structural analysis of black band disease-infected coral reveals boring cyanobacteria and novel bacteria. Dis Aquat Org 93:179-190.

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