Characterization, fluctuation and tissue differences in nutrient content in the Pacific oyster ( Crassostrea gigas ) in Qingdao, northern China

Abstract

The Pacific oyster (Crassostrea gigas) is one of the most important aquaculture species worldwide. Its meat quality is vital for consumer satisfaction, and nutrient content, especially glycogen, is closely associated with oyster fatness and meat colour. Fluctuations in nutrient content of short‐term starvation have not been previously reported, and seasonal variation in glycogen content in different tissues has rarely been reported. In the present study, we investigated these important aspects of oyster production and found that short‐term starvation (50 hr) did not significantly alter glycogen, protein or lipid content. The seasonal variation assay showed that glycogen and lipid accumulation was high in autumn and winter and that seawater temperature and protein content were inversely related to glycogen content. Glycogen content of the whole flesh was higher from January to April and was positively related to the condition index before the onset of gametogenesis. Glycogen content was higher in the gonad, labial palp and mantle compared to the gill or adductor muscle. Relative expression of genes encoding proteins involved in glycogen metabolism (glycogen synthase, glycogen phosphorylase, glycogen debranching enzyme and glycogen branching enzyme) was closely associated with the glycogen content in the corresponding tissues. Glycogen content in the gonad was regulated by glycogen metabolic and glycolysis pathway genes (6‐phosphofructo kinase, phosphoglycerate kinase, pyruvate kinase, hexokinase and glucose transporters), and stored glycogen was the main energy source for gametogenesis. These findings contribute to oyster aquaculture management and glycogen improvement and expand our understanding of glycogen metabolism in oysters.

Bimonthly variation in nutrient composition and taste components of Crassostrea gigas cultured in Rushan, Southern yellow sea

“…This trait corresponded to a previously reported study of the Pacific oyster (Crassostrea gigas) in Qingdao (Liu et al, 2019).…”

“…Crude protein content was higher in the summer, whereas the crude fat content was higher in winter and spring. To survive the low temperatures of winter and spring, oysters convert energy into lipids (Liu et al, 2019). At the same time, oyster gonads mature in the spring, improving fertility and storing fat in the body, thus, increasing the weight and fat content of individual oysters (Berthelin et al, 2000).…”

Molecular Basis of Taste and Micronutrient Content in Kumamoto Oysters (Crassostrea Sikamea) and Portuguese Oysters (Crassostrea Angulata) From Xiangshan Bay

“…Indeed, the small body size is a characteristic of Kumamoto oysters (Hedgecock et al, 1999;Melo et al, 2021). Protein, lipid, and glycogen contents of the two oyster species were comparable to those of other oyster varieties and glycogen content is believed to be related to oyster taste (Liu et al, 2020;Murata et al, 2020;Qin et al, 2020). A comparison of 31 domestic Crassostrea gigas strains revealed that oysters with a higher glycogen content were more often evaluated as "sweet" or "rich" (Murata et al, 2020).…”

“…An electronic balance (sensitivity = 0.01 g) was used to measure total weight (weight before shucking the oyster), soft weight (weight of soft body), and dry soft weight. Dry soft weight was measured after freeze-drying for 48 h; whereas the shells were oven-dried at 80°C for 48 h. The condition index was calculated as the percentage of soft weight relative to dry soft weight, the dressing percentage was calculated as the ratio of dry flesh weight relative to dry shell weight (Liu et al, 2020). The oysters were shucked, and the adductor muscle was selected for DNA extraction and subsequent species identification by specific molecular methods (Liu et al, 2021) and the results are summarized in Supplementary Figure 1.…”

“…The nutrient composition of different oyster species has been extensively studied in many areas (Oliveira et al, 2006;Pogoda et al, 2013;van Houcke et al, 2016;Qin et al, 2018;Yuasa et al, 2018;Zhu et al, 2018;Lin et al, 2019). Biochemical characteristics, volatile organic compounds, taste, and micronutrients vary among species (van Houcke et al, 2016;Yuasa et al, 2018;Lin et al, 2019), strains or brands of the same species (Zhu et al, 2018;Murata et al, 2020), tissues (Liu et al, 2013(Liu et al, , 2020, ploidy levels (Qin et al, 2018), and even culture conditions (Pennarun et al, 2003;van Houcke et al, 2017;Bi et al, 2021). While Kumamoto oysters seem to have a unique taste (Lin et al, 2019), the molecular basis underlying this characteristic remains unknown.…”