Fine structure and physicochemical studies on the collagen of the marine sponge Chondrosia reniformis Nardo

The sponge Chondrosia reniformis, devoid of inorganic spicules and of spongin fibres, is surrounded by a resistant dermis composed of dense fibrillar bundles and ground substance. After isolation and negative staining or shadowing, the individual fibrils, about 196 Å in diameter, display a distinct 660 Å periodicity and two main intraperiod bands. Ruthenium red and phosphotungstic acid staining reveal complex carbohydrates closely associated with the fibrils. Biochemical analysis, wide angle X ray diffraction, and infrared spectrum confirm the collagenous nature of the fibrils and the existence of associated carbohydrate-rich material. Thermal stability and tensile tests emphasize the influence of noncollagenous substances on the resistance of the tissues. The significance of this sponge collagen is discussed.