Jellyfish Rhopilema esculentum has been exploited commercially as a delicious food for a long time. Although the edible and medicinal values of R. esculentum have gained extensive attention, the effects of lipids on its nutritional value have rarely been reported. In the present of study, the lipid profile including lipid classes, fatty acyl compositions, and fatty acid (FA) positions in lipids from different parts (oral arms, umbrella, and mouth stalk) of R. esculentum was explored by ultraperformance liquid chromatography--electrospray ionization--quadrupole time-of-flight mass spectrometry (UPLC-ESI-Q-TOF-MS). More than 87 species from 10 major lipid classes including phosphatidylcholine (PC), lysophosphatidylcholine (LPC), phosphatidylethanolamine (PE), lysophosphatidylethanolamine (LPE), phosphatidylinositol (PI), lysophosphatidylinositol (LPI), phosphatidylserine (PS), ceramide (Cer), ceramide 2-aminoethylphosphonate (CAEP), and triacylglycerol (TAG) were separated and characterized. Semiquantification of individual lipid species in different parts of R. esculentum was also conducted. Results showed that glycerophospholipids (GPLs) enriched in highly unsaturated fatty acids (HUFAs) were the major compenents in all parts of R. esculentum, which accounted for 54-63% of total lipids (TLs). Considering the high level of GPLs and the FA compositions in GPLs, jellyfish R. esculentum might have great potential as a health-promoting food for humans and as a growth-promoting diet for some commercial fish and crustaceans. Meanwhile, LPC, LPE, and LPI showed high levels in oral arms when compared with umbrella and mouth stalk, which may be due to the high proportion of phospholipase A2 (PLA2) in oral arms. Moreover, a high CAEP level was detected in oral arms, which may render cell membranes with resistance to chemical hydrolysis by PLA2. The relatively low TAG content could be associated with specific functions of oral arms.
Taurine is usually included in fish feed as a nutritional supplement, and it can also improve feed performance. To assess the potential use of taurine as a feed attractant in plant protein-based diets, we examined four different concentrations of taurine to determine the optimal levels for attracting large yellow croaker (Larimichthys crocea). The fish displayed the most significant attractive responses to 3.5% taurine and showed good feed performance with an all-plant protein diet supplying 3.5% taurine. Next, deep sequencing of the olfactory epithelium was conducted to identify genes differentially expressed in the taurine group (Tau) versus controls.We found that 11,793 unigenes were differentially expressed: 10,795 were upregulated and 998 were down-regulated unigenes. We detected 77 olfactory receptor genes, including 37 up-regulated unigenes, and validated the expression dynamics of eight genes using quantitative reverse transcription-PCR (RT-qPCR). We utilized Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) to analyse the function of the differentially expressed genes, which were mainly involved in signaling and cell communication (GO) and olfactory transduction (KEGG). Cumulatively, our results indicate that taurine could be a good phagostimulant for plant protein-based diets for L. crocea. Furthermore, improved understanding via olfactory epithelium transcriptomic analysis would inform the development of an all-plant protein diet for L. crocea. K E Y W O R D S all-plant protein diets, Larimichthys crocea, olfactory-related genes, taurine, transcriptomic analysis for Zhejiang Marine High-Efficiency and
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