Comparison of the Biochemical Composition and Nutritional Quality Between Diploid and Triploid Hong Kong Oysters, Crassostrea hongkongensis.

Yanping Qin,Xiangwei Wu,Yuehuan Zhang,Shu Xiao,Riguan Mo,Jun Li,Haitao Ma,Ziniu Yu

doi:10.3389/fphys.2018.01674

Abstract

This study is the first systematic comparison of the biochemical composition and nutritional quality between diploid and triploid Hong Kong oysters, Crassostrea hongkongensis. Results showed that in the reproductive season, the glycogen content in five tissues (gill, mantle, adductor muscle, labial palps and gonad) was significantly higher (P < 0.05) in triploids than in diploids, with odds ratios (ORs) of 96.26, 60.17, 72.59, 53.56, and 128.52%, respectively. In the non-reproductive phase, significant differences in glycogen content (P < 0.05) between diploid and triploid oysters existed only in gill and gonad. In both diploid and triploid Hong Kong oysters, quantitative real-time PCR analysis of the glycogen synthesis gene (ChGS) and glycogen phosphorylase gene (ChGP) showed that the gene expression patterns matched the pattern of variation in glycogen content. Moreover, in both the reproductive and the non-reproductive phases, triploid Hong Kong oysters had a well balance of essential amino acids and were thus a well source of high-quality protein. Surprisingly, in both phases, significantly higher (P < 0.05) percentages of four essential fatty acids (α-linolenic acid, linoleic acid, eicosapentaenoic acid, and docosahexaenoic acid) were observed in triploids than in diploids. Additionally, the ratio of n-3/n-6 polyunsaturated fatty acids (PUFAs) was much higher in triploids than that in diploids. Variations in Biochemical composition were consistent with the relative expression of the citrate synthase gene (ChCS) and the α-ketoglutarate dehydrogenase gene (ChKD), which are key enzyme genes of the tricarboxylic acid cycle. Overall, the triploid Hong Kong oyster has a better nutritional value and taste than the diploid in terms of glycogen content, protein quality and fatty acid content.

Highlights

Due to their rapid growth and maintaining good taste in the reproductive phase, many triploid bivalves have entered into commercial farming, including oysters (Allen and Downing, 1986; Houcke et al, 2016), scallops (Racotta et al, 2008), clams (Utting and Child, 1994; Shpigel and Spencer, 1996), and mussels (Zwaan and Zandee, 1972; Dare and Edwards, 1975)
No solid comparative data is available on the differences in the biochemical compositions and nutritional qualities between diploid and triploid Hong Kong oysters, which are very important for promoting the application of triploid Hong Kong oysters in the industry
We found that the glycogen content of some tissues was lower during the reproductive season than in the non-reproductive phase in diploid oysters, especially in the labial palps and gonad, which had odds ratios (ORs) of −51.60 and −49.70% comparing the reproductive to the non-reproductive phase

Summary

Introduction

Due to their rapid growth and maintaining good taste in the reproductive phase, many triploid bivalves have entered into commercial farming, including oysters (Allen and Downing, 1986; Houcke et al, 2016), scallops (Racotta et al, 2008), clams (Utting and Child, 1994; Shpigel and Spencer, 1996), and mussels (Zwaan and Zandee, 1972; Dare and Edwards, 1975). No solid comparative data is available on the differences in the biochemical compositions and nutritional qualities between diploid and triploid Hong Kong oysters, which are very important for promoting the application of triploid Hong Kong oysters in the industry. Like many other oyster species, diploid Hong Kong oysters have an inferior taste and low meat quality during the reproductive season (from May to August) each year, which can be attributed to gametogenesis (Lam and Morton, 2003; Bacca et al, 2005; Wang et al, 2015; Zhang et al, 2017). Gametogenesis in triploids is retarded in the reproductive season, since triploid oysters have poorly developed gonads compared to diploids. According to previous studies on diploid Tapes philippinarum (Shpigel and Spencer, 1996), Crassostrea gigas (Soudant et al, 1999; Dridi et al, 2007; Pogoda et al, 2013), Ostrea edulis (Houcke et al, 2016), and Crassostrea virginica (Zeng et al, 2015), large changes in biochemical composition occur in response to gonad development

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Results

Conclusion