High-Throughput Sequencing Reveals the Effect of Feeding on Overwintering Hirudo nipponia

Abstract

To investigate the effect of feeding on hibernating Hirudo nipponia, metagenomic sequencing was performed on the microorganisms collected from the digestive tract of H. nipponia individuals that were fed (FW) or starving (SW) before hibernation. In addition, the salivary gland tissues were obtained from these individuals to conduct transcriptome sequencing. Results showed that feeding before hibernation increased the relative abundance of Bacteroidetes and Proteobacteria at the phylum level and that of Aeromonas, Mucinivorans, Bacteroides, and Desulfovibrio at the genus level. Functional prediction results indicated that feeding before hibernation not only improved metabolic capacity but also increased the susceptibility of H. nipponia to pathogens. Among the 133,082 unigenes obtained by transcriptome sequencing, a total of 2801 differentially expressed genes (DEGs) were found, of which 355 were up-regulated and 2446 were down-regulated; the expression patterns of 15 selected DEGs were validated by qRT-PCR. Results from the GO and KEGG enrichment analyses showed that a majority of these DEGs were involved in the signal transduction pathways. This study established a basis for H. nipponia breeding during hibernation through analyses of the abundance of microorganisms in the digestive tract and the gene expression pattern of salivary glands by high-throughput sequencing. The findings also revealed the effect of feeding on the expression of both gastrointestinal microorganisms and salivary gland genes of hibernating H. nipponia.