Antibacterial and antisettlement activity of the dogfish (Scyliorhinus canicula) eggcase

The dogfish eggcase protects the developing embryo for up to a year against predation and fouling. The mechanical protection is provided by the strength and resilience of the case. The aim of this study was to determine the mechanisms underlying the case's antifouling proficiency. The eggcase is constructed of oxidatively cross-linked proteins, which are primarily collagen. Two main hypotheses were examined, firstly that the egg case scavenges heavy metals and these act as deterrents. Secondly, the tanning agents, particularly dihydroxyquinones, through reaction with Fe2+, produce hydroxy radicals that act as deterrents. This process is called the Fenton reaction. Using ten different species of marine bacteria, Semibalanus cyprids and Enteromorpha zoospores, a variety of experiments were conducted to examine the effect of surface chelation, iron loading, changing the surface roughness, different collagen types and quinones, and the presence of antioxidants. The results suggest that the photoactivated generation of free radicals is partially responsible for the antifouling mechanism of the eggcase. Collagen and quinone chemistry and surface integrity are also considered to be important in the antifouling process.