Cholesterol is an important essential nutrient for crustaceans. This experiment investigated the effects of dietary cholesterol on the osmoregulation, antioxidant defense, immune response and salinity stress resistance of Pacific white shrimp (Litopenaeus vannamei). Six diets (Chol 1.0, Chol 1.4, Chol 1.8, Chol 2.2, Chol 2.6, and Chol 3.0) with cholesterol levels of 0.1%, 0.14%, 0.18%, 0.22%, 0.26% and 0.30% were prepared and fed on shrimp (1.27 ± 0.18 g) for 56 d, followed by the low salinity stress experiment for 144 h. Sampling was conducted at 56 d and 24, 72, 144 h during salinity stress. At 56 d, cholesterol enhanced the growth performance of L. vannamei by promoting transport and absorption of endogenous lipid. Dietary 0.22%–0.30% cholesterol could enhance the antioxidant defense and immune response of shrimp. After salinity stress, Na⁺, Cl⁻ and K⁺ ion concentrations and osmolality in hemolymph were decreased significantly (P < 0.05), and the Na⁺ concentration and osmolality of hemolymph in Chol 2.2–3.0 groups were significantly higher than those in Chol 1.0–1.4 groups (P < 0.05). After 24 h and 72 h of salinity stress, Na⁺/ K⁺- ATPase (NKA) activity in Chol 2.2–3.0 groups was significantly higher than that in Chol 1.0–1.4 groups (P < 0.05). The plasma dopamine (DA), norepinephrine (NE) and serotonin (5-HT) contents increased significantly at 24 h and recovered at 144 h in all groups (P > 0.05) with no significant differences in biogenic amines contents among all groups at the same time points (P > 0.05), indicating that cholesterol could improve the osmoregulation of L. vannamei by directly enhancing NKA activity independent of the regulation of biogenic amines. Dietary 0.26%–0.30% cholesterol could enhance the osmoregulation and salinity stress resistance of shrimp and protect against biomacromolecule damage induced by oxidative stress and ion toxicity. Insufficient cholesterol intake (below 0.1%) may presumably cause the death of shrimp by affecting the NKA conformation. Under physiological conditions, the optimum level of dietary cholesterol in shrimp feed was about 0.22%, while it was 0.26% - 0.3% under salinity stress.

胆固醇是甲壳类动物的重要必需营养素。本实验研究了日粮胆固醇对南美白对虾（Litopenaeus vannamei）渗透压调节、抗氧化防御、免疫反应和盐胁迫抗性的影响。制备胆固醇水平分别为 0.1%、0.14%、0.18%、0.22%、0.26% 和 0.30% 的六种日粮（Chol 1.0、Chol 1.4、Chol 1.8、Chol 2.2、Chol 2.6 和 Chol 3.0）并以虾为食（ 1.27 ± 0.18 g) 56 d，然后进行 144 h 的低盐胁迫实验。在盐分胁迫期间的 56 d 和 24、72、144 h 进行采样。56 d时，胆固醇提高了南美白对虾的生长性能通过促进内源性脂质的转运和吸收。日粮中0.22%~0.30%的胆固醇可以增强虾的抗氧化防御和免疫反应。盐胁迫后血淋巴中Na ⁺、Cl ^-和K ⁺离子浓度和渗透压显着降低（P  < 0.05），Chol 2.2~3.0组血淋巴Na ⁺浓度和渗透压显着高于Chol 1.0组–1.4 组 ( P  < 0.05)。盐分胁迫24 h和72 h后，Chol 2.2~3.0组的Na ⁺ / K ⁺ - ATP酶（NKA）活性显着高于Chol 1.0~1.4组（P < 0.05)。各组血浆多巴胺（DA）、去甲肾上腺素（NE）和5-羟色胺（5-HT）含量在24 h显着升高，144 h恢复（P  > 0.05），各组间生物胺含量差异无统计学意义。相同的时间点（P  > 0.05），表明胆固醇可以改善南美白对虾的渗透压调节通过独立于生物胺的调节直接增强 NKA 活性。日粮中0.26%~0.30%的胆固醇可以增强虾的渗透压调节和盐分胁迫抵抗力，防止氧化应激和离子毒性引起的生物大分子损伤。胆固醇摄入不足（低于 0.1%）可能通过影响 NKA 构象而导致虾死亡。生理条件下，虾饲料中日粮胆固醇的最佳水平约为0.22%，而盐胁迫下为0.26%～0.3%。