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BackgroundChemosensory receptors, which are all G-protein-coupled receptors (GPCRs), come in four types: odorant receptors (ORs), vomeronasal receptors, trace-amine associated receptors and formyl peptide receptor-like proteins. The ORs are the most important receptors for detecting a wide range of environmental chemicals in daily life. Most fish OR genes have been identified from genome databases following the completion of the genome sequencing projects of many fishes. However, it remains unclear whether these OR genes from the genome databases are actually expressed in the fish olfactory epithelium. Thus, it is necessary to clone the OR mRNAs directly from the olfactory epithelium and to examine their expression status.ResultsEighty-nine full-length and 22 partial OR cDNA sequences were isolated from the olfactory epithelium of the large yellow croaker, Larimichthys crocea. Bayesian phylogenetic analysis classified the vertebrate OR genes into two types, with several clades within each type, and showed that the L. crocea OR genes of each type are more closely related to those of fugu, pufferfish and stickleback than they are to those of medaka, zebrafish and frog. The reconciled tree showed 178 duplications and 129 losses. The evolutionary relationships among OR genes in these fishes accords with their evolutionary history. The fish OR genes have experienced functional divergence, and the different clades of OR genes have evolved different functions. The result of real-time PCR shows that different clades of ORs have distinct expression levels.ConclusionWe have shown about 100 OR genes to be expressed in the olfactory epithelial tissues of L. crocea. The OR genes of modern fishes duplicated from their common ancestor, and were expanded over evolutionary time. The OR genes of L. crocea are closely related to those of fugu, pufferfish and stickleback, which is consistent with its evolutionary position. The different expression levels of OR genes of large yellow croaker may suggest varying roles of ORs in olfactory function.

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.

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Silver pomfret (Pampus argenteus) is an economically important mariculture species. However, little is known about the genetic parameters of its commercially important traits. In order to determine whether continuous progress can be achieved by selection for growth, we took the body weight trait of East China Sea P. argenteus as the target trait of mass selection. The realized heritability of P. argenteus from the selected group and control group was analyzed at the three growth times (60, 90, and 120 days). The results showed that the growth performance parameters of the selected group in the third month post hatching were higher than those in the control group, but the opposite results were found in the fourth month. The morphological traits highly correlated with the body weight of P. argenteus were found by Pearson correlation analysis and path analysis, which were body length and tail length, respectively. On the 60th, 90th, and 120th days after hatching, the genetic gains of body weight trait in the selected group were 9.44%, 17.64%, and 15.18%, respectively, and the mean values of realized heritability were at moderate level. Nevertheless, in the selected group, the genetic variation values of the two morphological traits significantly related to body weight were all below 10%, and the genetic gains were relatively low and stable, but the genetic variation values of body weight trait in the selected group were above 20%, and genetic gains were relatively high. These implied that it is possible to obtain considerable genetic gains by selecting for body weight trait, and the results provide supportive evidence for the continuity of the P. argenteus-selective breeding program.