Sexual size dimorphism in golden pompano (Trachinotus blochii): potential roles of changes in energy allocation and differences in muscle metabolism

Sexual size dimorphism describes the size difference between male and female individuals of the same species and has been observed in many farmed fish species. The golden pompano (Trachinotus blochii) is becoming increasingly popular among consumers and has high yields, and growth differences between males and females are also concerned. In this study, by continuously measuring the growth performance of golden pompano, comparing the growth differences between males and females, and performing transcriptome analysis of muscle tissue, which try to clarify the molecular mechanism of the sexual dimorphism in the growth traits. There was a significant difference in growth between males and females (p < 0.05), females are 17% larger than males after 7-month-old. Through RNA-seq analysis, we identified 2132 differentially expressed genes, which were mainly involved in signal pathways and metabolic processes. Among them, a higher level of leptin receptor and a cell energy sensor for regulating the intracellular nutrition level (i.e., PRKAA), displayed up-regulated patterns in the muscle at LS, respectively. But the GLUT1, GLUT4, LDH, and GYS genes were significantly lower than in males, these data suggested that glucose uptake and glycogen synthesis were inhibited, but the glucose metabolism was enhanced. The expression levels of several adipose-related genes, including ACSL1, CPT2, ACADM, and ACAA2, were higher in females than males at the late stage. Our results showed that the catabolism of 7 non-essential amino acids and 3 essential amino acids was enhanced. It is worth noting that the synthesis of arginine and omithine, and the production of carnosine were enhanced, but the breakdown of glutamine is inhibited. Our results support a certain negative correlation between gonadal development and muscle metabolism, depending on differences in energy distribution. AMPK signaling pathway and adipocytokine signaling pathway plays an important regulatory role in the muscle growth and metabolism of golden pompano. Comparing male and female individuals at the late stage, it was found that the metabolism of glucose, lipid, and amino acid in females was up-regulated, and the ability of oxidative phosphorylation was stronger. This may be a potential reason why the golden pompano females show better growth performance in later stages of growth.