Abstract
The eyestalk of crustacean species secretes many hormones, affecting the process of reproduction, molting, metabolism of glucose, and other functions in crustaceans. In this study, important metabolic pathways and candidate genes involved in the male sexual development were identified through performing the transcriptome profiling analysis of the testis after the ablation of eyestalk from Macrobrachium nipponense. The histological observations revealed that the testis development became vigorous after eyestalk ablation, indicating that the hormones secreted by the eyestalk have negative effects on the testis development in M. nipponense. Transcriptome profiling analysis revealed that 1,039, 1,226, and 3,682 differentially expressed genes (DEGs) were identified between normal prawns (CG) vs single-side eyestalk ablation prawns (SS), SS vs double-side eyestalk ablation prawns (DS), and CG vs DS, respectively, indicating that the ablation of double-side eyestalk has more significant regulatory roles on male sexual development than that of single-side ablation, which was consistent with the histological observations. Lysosome, Apoptosis, Glycolysis/Gluconeogenesis, and Insulin signaling pathway were the main enriched metabolic pathways in all of these three comparisons, and the important genes from these metabolic pathways were also selected. The qPCR verifications of 10 DEGs from these metabolic pathways were the same as those of RNA-seq. The qPCR, in situ hybridization, and RNA interference analysis of Mn-NFkBα revealed that NFkBα has a positive regulatory effect on testis development. This study provided new insights on male sexual development in M. nipponense, promoting the studies on male sexual development in other crustaceans as well.
Highlights
The oriental river prawn, Macrobrachium nipponense (Crustacea; Decapoda; and Palaemonidae), is widely distributed in China and other Asian countries (Cai and Shokita, 2006; Salman et al, 2006; Ma et al, 2011), which is an important commercial species with annual aquaculture production that reached 205,010 tons in 2016 (Wang et al, 2019)
Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that Lysosome, Apoptosis, Insulin signaling pathway, and Glycolysis/Gluconeogenesis were the main enriched metabolic pathways in all of these three comparisons
The histological observations of the testis after eyestalk ablation from M. nipponense indicated that the number of sperms in the double-side eyestalk ablation prawns (DS) prawns was significantly more than that of side eyestalk ablation prawns (SS) prawns and CG prawns, and spermatogonia were rarely observed in the DS prawns
Summary
The oriental river prawn, Macrobrachium nipponense (Crustacea; Decapoda; and Palaemonidae), is widely distributed in China and other Asian countries (Cai and Shokita, 2006; Salman et al, 2006; Ma et al, 2011), which is an important commercial species with annual aquaculture production that reached 205,010 tons in 2016 (Wang et al, 2019). The same as other Macrobrachium species, male prawns grow faster and reach larger size at the harvest time (Ma et al, 2011). Male prawns are preferred in the M. nipponense aquaculture. Previous studies revealed that the testis of a newborn M. nipponense can reach sexual maturity within 40 days after hatching (Jin et al, 2016). It is urgently needed to fully understand the male sexual determination and development mechanism, especially for the identification of the key metabolic pathways and genes involved in the mechanism of male sexual determination and development in M. nipponense, with the aims of establishing the technique to produce all male progeny on a commercial scale and regulating the process of testis development
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