Transcription profiles and fatty acid composition of the artificial induced triploid alevin in Atlantic salmon Salmo salar

Triploid Atlantic salmon Salmo salar is commercially available and ideal means of achieving sterility in fish. The expression patterns of triploid parr and smolt were described before. However, little is known about the gene expression and fatty acid composition of triploid alevins at endogenous nutritional stage, which is an important period for their survival and development. In this study, the development of the diploid and triploid Atlantic salmon embryos and hatched alevins before feeding was compared, and the results showed that there was no obvious morphological difference between them. And then, the transcription profiles of the triploid and diploid alevins on 3, 23 and 33 days post hatching (dph) were investigated by using RNA-seq after the yolk sacs were removed. There were more differentially expressed genes (DEGs) on 3 dph (2925) than those on 23 (589) and 33 dph (606). Compared with the diploid groups, the up-regulated genes in the triploid groups at the three sampling times were 1189, 339 and 340, respectively, while 1736, 250 and 266 genes were down-regulated. There were 2088 and 5215 DEGs on 23 and 33 dph compared with on 3 dph in the diploid groups, while 6533 and 9340 DEGS on 23 and 33 dph compared with 3 dph in the triploid groups. The functional enrichment analysis showed that the DEGs were mainly enriched to digestion and metabolism function, especially on 33 dph when the larvae were about to feeding. Meanwhile, 15 out of 22 kinds of fatty acids of alevins on 33 dph showed significant differences (P < 0.05), in which all the fatty acids contents in the triploid were lower. The results indicated the specific nutritional requirement in the triploid was represented as early as yolk sac stage. The present study gave an important vision in triploid Atlantic salmon breeding.