Skeletal Eroding Band - Agent Identified

Agent Identified

So far one agent has been identified, the folliculinid ciliate protozoan Halofolliculina corallasia. Skeletal eroding band is the first recorded disease of corals that is caused by a protozoan, and the first caused by a eucaryote – most are caused by bacteria. For example, black band disease is caused by microbial mats of variable composition, and White pox disease by the bacterium Serratia marcescens.

H. corallasia is a sessile unicellular organism that secretes a bottle-like housing called a lorica (Latin for cuirass, flexible body armor), that is anchored to a surface and into which the cells retract when disturbed. When a mature individual cell division divides, it produces a pair of worm-like larvae that settle on undamaged coral just ahead of the black band. There each daughter cell secretes its lorica, at the same spinning to produce the lorica's flask-like shape. This spinning, combined with the chemicals that harden the lorica, crumble the coral skeleton and kill the polyps. The discarded loricae of the "parent" H. corallasia cells remain, leaving the distinctive spotted region in the wake of the living black band.