Variation of lipid classes among organs of the Northern krill Meganyctiphanes norvegica, with respect to reproduction

Abstract

Lipid content and class in the Northern krill Meganyctiphanes norvegica (digestive gland, stomach, gonad, fat body, abdomen) was investigated and correlated with sex and reproductive stage. Ready to spawn females, have high lipid content in ovaries, while in males and spent females, the major site of lipid deposits was the digestive gland, followed by the fat body. These differences among spawning and spent females are indicative of strong interactions between the ovary and digestive gland and the ovary and fat body during vitellogenesis. Triacylglycerols (TAG) were the major neutral lipid class with high levels in the digestive gland. The major phospholipid was phosphatidylcholine (PC) particularly in the muscular tissue of the abdomen. Phosphatidyl-ethanolamine (PE) and –serine–inositol (PS–PI), were present at intermediate levels. Reproductive males were depleted in TAG and diacylglycerols (DAG) in the digestive gland, gonad and fat body, and had 4 times lower cholesterol in the gonad than ready to spawn females. Furthermore, ready to spawn females had in the ovary higher amounts of TAG, DAG and phospholipids (PC, PE, PS–PI) than spent females. Linear relationships between lipid content and main lipid class (TAG, PC, PE, PS–PI) in different fractions of males and ready to spawn females showed that: (1). TAG was stored for both sexes in all cephalothorax fractions with highest values in the digestive gland and ovary fluid; (2). PC was accumulated for both sexes in the fat body and the gonad with a higher slope for females, with the highest values in the ovary fluid and in the abdomen of males and that (3). PS–PI was stored only in the ovary and abdomen of mature females. These results are discussed in terms of the strategy developed by Meganyctiphanes norvegica to allocate lipids to the next generation for optimised embryogenesis.