Vacelet, J.; Vacelet, E.; Gaino, E.; Gallissian, M.-F. (1994). Bacterial attack of spongin skeleton during the 1986-1990 Mediterranean sponge disease. in: Sponges in Time and Space, van Soest, van Kempen & Braekman (eds) Balkema. Rotterdam. pp 355-362.
Since 1986, a disease has affected the Mediterranean populations of dictyoceratid sponges,
including commercial species. A program for studying the disease and its economic impact on the sponge fishing industry was developed by the Food and Agriculture Organization of the United Nations (FAO). The program involved observations on dead or dying specimens of genera Spongia, Hippospongia, Sarcotragus and Ircinia collected on the affected sponge grounds. As in previous studies, bacterial digestion of the spongin fibres was observed in the exposed dead parts of the skeleton in dying sponges. However, similar bacteria were observed boring into spongin fibres in two othercircumstances: (i) skeletons of the otherwise healthy living parts of sponges attacked by the disease, and (ii) naked skeletons ofhealthy sponges experimentally killed and exposed in sea water for several months. These results raise the possibility that bacteria which normally degrade dead spongin skeletons may become virulent and digest the spongin fibres inside the living tissue of attacked sponges. Isolation of this presumed pathogen was not conclusive, and so it is unknown whether these bacteria are involved as the primary or the secondary agent in the disease. Digestion of the skeleton implies that the bacteria secrete a collagenase active
on spongin, which is resistant to commercially available enzymes. The virulence of the disease appears to be related to relatively high sea water temperatures, as sponges have been less affected in the northern zones of the Mediterranean and below 40 m in depth. Prolonged, heavy exploitation of Mediterranean commercial sponges may have increased the virulence and dispersal of the pathogen.