Characterisation of 4α-methyl sterols in Pavlova spp. and postlarval sea scallops, Placopecten magellanicus

Dietary sterols are necessary to ensure the growth of bivalves such as the commercially important sea scallop, Placopecten magellanicus. 4α-methyl sterols are large C30–C34 sterols present in dinoflagellates and prymnesiophytes, and are thus encountered by scallops in both hatchery and natural environments. Those present in the two classes are very similar with the same number of carbon atoms, the same number of double bonds and the same ions in a mass spectrum. There is, however, a subtle but perhaps biochemically important difference in the side chain in that one group of compounds has an ethyl group (CH3CH2) while the other has two methyl groups (CH3). The ethyl group produces a small difference in retention times on a gas chromatography (GC) column and a small difference in the intensity of key ions in certain mass spectrometers. The ethyl group may also be responsible for discrimination against this compound by the sea scallop.