Krill oil: A high quality phospholipid source for ovary development of female red claw crayfish, Cherax quadricarinatus

Three isonitrogenous and isolipidic experimental diets (2% supplement with soy lecithin, egg yolk lecithin, or krill oil) and one control diet (without phospholipid supplement) were formulated for female red claw crayfish Cherax quadricarinatus for 10 weeks. Results indicated that phospholipid supplement can improve gonadosomatic index, especially in krill oil diet treatment. C. quadricarinatus fed diet with soybean lecithin showed the highest hepatosomatic index. Krill oil diet is more effective than soy lecithin and egg yolk lecithin diets in promoting hepatosomatic and ovarian lipid deposition (including total cholesterol and triglyceride). Krill oil in diet also can improve the accumulation of yolk granule and increase the ratio and diameter of marine oocytes. Supplement with phospholipid increased the serum high-density lipoprotein concentration and ovarian methyl farnesoate, estradiol and progesterone contents, especially in crayfish fed with krill oil diet. Low-density lipoprotein in serum and gonadal inhibitory hormone and molting inhibitory hormone concentration in eyestalks were all decreased significantly in crayfish when fed diets with phospholipid supplement. Furthermore, crayfish fed diet with krill oil showed significantly lower malondialdehyde content and higher specific activities of superoxide dismutase, a total antioxidant enzyme, and glutathione peroxidase in hepatopancreas than other experimental treatments. Ovarian lipidomics results indicated that phosphatidylcholine and phosphatidylethanolamine are two primary lipid molecules response to dietary phospholipid. Among these lipids, long chain polyunsaturated fatty acids were important participants in ovarian development of crayfish. Combined transcriptome and lipidomics analysis showed that krill oil diet can improved ovarian development of C. quadricarinatus by improve related gene expressions of steroid hormone biosynthesis, sphingolipid signaling pathway, retinol metabolism, regulation of lipolysis in adipocytes and pancreatic secretion. Therefore, krill oil can be an excellent phospholipid source for C. quadricarinatus adult at the stage of gonadal development.