Growth and Lipidomic Responses of Juvenile Pacific White Shrimp Litopenaeus vannamei to Low Salinity

Abstract

The Pacific white shrimp (Litopenaeus vannamei), a euryhaline penaeid species, can tolerate a wide range of salinities, but little is known on its strategies to cope with low salinity fluctuations from the aspect of lipidomics. Thus, in this study, L. vannamei were grown in two different salinities [3 and 30‰ (control)] for 8 weeks, and then an liquid chromatography (LC)-mass spectrometry (MS)-based lipidomics analysis was performed to reveal the lipid profile differences in gill and muscle. L. vannamei under low salinity had lower weight gain and condition factor than the control shrimp at 30‰, but no differences were found in survival and hepatopancreas index. A higher number of differential lipid metabolites were identified in gill than in muscle in L. vannamei at salinity 3‰ relative to the control shrimp at salinity of 30‰ (159 versus 37), which belonged to 11 and 6 lipids classes, respectively. Of these lipids, phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidic acid (PA), phosphatidylethanolamine (PE), and triglyceride (TG) were the main lipids in both shrimp gill and muscle, regardless of salinities. Compared with the control shrimp at salinity 30‰, the percentage of PC significantly reduced, but TG and PA significantly increased in gill of shrimp at salinity 3‰. Moreover, the relative fatty acid abundances showed significant changes in L. vannamei between the two salinity groups, but the patterns of the changes were complex and were fatty acid dependent. Neither lipid nor fatty acid composition in muscle was affected by salinity. Further pathway analysis showed that these metabolites were closely related to lipid and fatty acid metabolic pathways. All the findings in this study reveal that the lipid variations are closely related to bio-membrane structure, mitochondrial function, energy supply, or organic osmolyte contents in hemolymph for improving osmoregulatory capacity of L. vannamei under low salinity.

Keywords: Litopenaeus vannamei; gill; growth; lipidomics; muscle; salinity.

FIGURE 1

The weight gain (%), survival (%), hepatosomatic index (%), and condition factor (%) of L. vannamei at 30 and 3‰ salinity. Data are presented as the mean ± SEM (n = 4). Two asterisks (^∗∗) indicate a highly significant difference (P < 0.01) between two salinities.

FIGURE 2

Typical total ion chromatograms from gill samples at 30 (A, ESI⁺ mode; B, ESI^– mode) and 3‰ salinity (C, ESI⁺ mode; D, ESI^– mode) and muscle samples at 30 (E, ESI⁺ mode; F, ESI^– mode) and 3‰ salinity (G, ESI⁺ mode; H, ESI^– mode).

FIGURE 3

PCA scores plot of gills and muscles at two salinities. (A) ESI⁺ and (B) ESI^–. Circle (brown), muscles at 30‰ salinity; star (blue), muscles at 3‰ salinity; triangle (red), gills at 30‰ salinity; and rhombus (green), gills at 3‰ salinity.

FIGURE 4

OPLS-DA scores plot (A: ESI⁺; B: ESI^–) and permutation test plots with a 200 permutation number (C: ESI⁺; D: ESI^–) of gills at two salinities. The permuted Q² (blue) values located on the left side of the graph were lower than the original points to the right, indicating the validity of the OPLS-DA model.

FIGURE 5

OPLS-DA scores plot (A: ESI⁺; B: ESI^–) and permutation test plots with a 200 permutation number (C: ESI⁺; D: ESI^–) of muscles at two salinities. The permuted Q² (blue) values located on the left side of the graph were lower than the original points to the right, indicating the validity of the OPLS-DA model. The data obtained from muscles in ESI⁺ were not available.

FIGURE 6

The relative abundance of specific lipids in total lipids (A) and the positional distribution of individual fatty acids in total TG (B), total PC (C: sn-1 position; D: sn-2 position), and total PE (E: sn-1 position; F: sn-2 position) in gills of L. vannamei. Values are means ± SEM (n = 4). One asterisk (^∗) and two asterisks (^∗∗) indicate significant differences (P < 0.05) and highly significant differences (P < 0.01) between two salinities, respectively.

FIGURE 7

The relative abundance of specific lipids in total lipids (A) and the positional distribution of individual fatty acids in total TG (B), total PC (C: sn-1 position; D: sn-2 position), and total PE (E: sn-1 position; F: sn-2 position) in muscles of L. vannamei. Values are means ± SEM (n = 4). One asterisk (^∗) and two asterisks (^∗∗) indicate significant differences (P < 0.05) and highly significant differences (P < 0.01) between two salinities, respectively.

FIGURE 8

Summary of pathway analysis in gill (A) and muscle (B) with MetaboAnalyst 4.0. (a) Glycerophospholipid metabolism; (b) glycerolipid metabolism; (c) linoleic acid metabolism; (d) alpha-linolenic acid metabolism; (e) arachidonic acid metabolism; (f) glycosylphosphatidylinositol (GPI)-anchor biosynthesis.