A comparative study of the collagen of the foot ofLamellidens Sp. and that of the unmodified part of the foot inMytilus edulis shows marked differences in physical properties, amino acid composition and in the degree of stabilization. But both conform to type I collagen of vertebrates. In these respects, the latter shows agreement with the features characteristic of byssus collagen, which is highly crosslinked, involving dimers and trimers of tyrosine. It is suggested that such differences may reflect the different functions of the organs concerned, the foot ofLamellidens being a locomotary organ of the animal, while the foot ofMytilus edulis is modified for anchorage of the animal. The vertigial part though not morphologically modified shows the essential compositional characteristics of the byssus being a mere remanant of it.

Collagen has been prepared from the skin of an air-breathing Indian fish(Ophiocephalus striatus) by extraction with cold 0.5M acetic acid and purification by alternate precipitation with NaCl and dialysis against 0.02M Na₂HPO₄. The purified collagen was characterised with respect to physico-chemical properties, amino acid composition and chromatography of the denatured collagen. The fish collagen has a higher shrinkage temperature and denaturation temperature compared to that of the allied teleosts living in exclusively aquatic medium. These differences could possibly be reflections of the response to the rigours of the environment. As found for other vertebrate collagens, the fish collagen contains two kinds of single chains the α₁ and α₂ chains as revealed by sodium dodecyl sulphate-polyacrylamidegel electrophoresis and carboxymethylcellulose chromatography.

The muscle collagen of marine prawn,Penaeus indicus, was isolated by limited pepsin digestion. Based on selective salt precipitation, amino acid composition and gel electrophoretic pattern, the major collagen was found to be a homotrimer of á 1 chain, similar to type V collagen of vertebrates. Electron microscopy of reconstituted fibrils, made for the first time from a crustacean species, revealed a characteristic 64 nm periodicity. Biochemical studies indicate a less than normal amount of associated carbohydrates and an increased alanine content The major collagen had a denatu ration temperature of 37°C with an intrinsic viscosity of 11.3 dl/g. Spectral characteristics of the major collagen were studied. Results suggest the presence of genetically distinct collagen types and acid resistant cross links in crustacean muscle.