Variation in lipid classes during the molting cycle of the prawn Penaeus japonicus

The variation in the concentration and fatty acid composition of lipid classes during the molting cycle of the prawn Penaeus japonicus was investigated. The lipid concentration of the whole body reached a maximum at mid-premolt (Stage D₂) and then decreased to low level at late premolt (Stage D_3–4). The accumulation of lipids during the premolt period seemed to be attributable to the increase of both polar and neutral lipids. The increase of neutral lipids at Stage D₂ was derived from not only triglycerides but also free sterols and free fatty acids. Regarding the fatty acid composition of every lipid class, a marked variation occurred mainly at the intermolt (Stage C). In this stage, the polar lipids were rich in monoenoic acids such as 18:1 and poor in polyenoic acids such as 20:53 and 22:63. The triglycerides were rich in polyenoic acids at Stage C, but poor in monoenoic acids such as 16:1 and 18:1. The steryl esters contained large amounts of saturated acids such as 16:0 and 18:0 throughout the molting cycle, however the level of polyenoic acids increased at Stage C.