Improving gonad colour and somatic index in the European sea urchin Paracentrotus lividus

The dominant carotenoid in the gonads was echinenone, which the sea urchin synthesises from β-carotene. The higher the echinenone level in the gonads, the more intense their colouration. The lack of echinenone found in the gut and its high accumulation in the gonad, in inverse proportion to the β-carotene profile, indicates bioconversion within the gonad or upon transfer from the gut to the gonad.