Marine organism can contain a very wide range of components containing atoms of arsenic, and these include lipids, although they are usually present at low levels. Some authors take a rather wide view of what constitutes an arsenolipid and thus include compounds such as trimethylarsine and its metabolites as lipids, simply on the basis of their solubility in organic solvents. Here, only those lipids that have been characterized sufficiently to be certain that they contain long alkyl-chains together with arsenic atoms somewhere in the molecule are considered