Isolation and structural studies of a sulfated sialosphingolipid from the sea urchin Echinocardium cordatum.  Three sialosphingolipids have been isolated from a lipid extract of gonads of the sea urchin Echinocardium cordatum by partition dialysis and DEAE-cellulose column chromatography. The structure of the sialosphingolipid containing sulfate group has been established. On the basis of the results of total and partial acid hydrolysis, methanolysis, methylation, periodate oxidation and enzymatic hydrolysis with neuraminidase the sulfated sialosphingolipid was identified as 8-sulfate-sialyl-alpha-(2 leads to 6)glucopyranosyl-(1 leads to 1)ceramide. The long-chain bases were mainly phytosphingosine and its C16 homologue. The fatty acids of the sialosphingolipid were the mixture of normal and alpha-hydroxy fatty acids, their compositions were analysed by gas-liquid chromatography.