Female lumpsuckers, Cjdopterus lumpus L., have blue-green blood serum and subcutaneous gelatinous tissue; the male's are red/magenta in colour. The female serum contains a chromoprotein with biliverdin as the prosthetic group; the male serum contains the same biliverdin pigment but this is normally masked by a red pigment, probably phycoerythrin. The female serum also contains the red pigment but at a much lower concentration than in the male. These bile pigments are probably formed by the breakdown of haem in the liver. Lumpsucker gall bladders are relatively small and do not enlargeduring starvation. Storage ofbile pigments in theserumand subcutaneous jelly may have arisen in response to the problems of regular long-term starvation. The pigments now appear to have an additional sexual signalling function.