Myo-inositol accelerates the metamorphosis from megalopa to crablet of Scylla paramamosain by modulating cuticle decomposition and reconstruction

The mud crab Scylla paramamosain is a key species in China due to its high nutritional value and great economic worth and has grown in popularity. Myo-inositol can modulate versatile physiological functions in aquatic animals. In the present study, S. paramamosain megalopa were given graded concentrations of myo-inositol (0, 1, 2, 4, and 8 ppm) by water immersion to explore how their metamorphosis would be affected. The results showed that supplementing with myo-inositol remarkably increased transformation and survival rate from megalopa to crablet by at least 1.16 and 1.26 times, respectively. To decipher the molecular mechanism of how myo-inositol increases metamorphosis and survival rate, we further performed transcriptome-based gene expression profiling of both megalopa and crablet treated with myo-inositol. The integrative transcriptome analyses predicted that the differentially expressed genes (DEGs) were significantly enriched in chitinase activity, structural constituent of cuticle, and chitin binding, which are associated with the decomposition and reconstruction of cuticle. qPCR results confirmed that myo-inositol mediated gene expression levels of the above cuticle-related pathways. Considering the importance of the cuticle in exoskeleton formation and molting, it can be concluded that myo-inositol-induced changes in the cuticle decomposition and reconstruction might have accelerated the transformation from megalopa to crablet of S. paramamosain. Besides, numerous DEGs were significantly enriched in protein digestion and absorption, amino sugar and nucleotide sugar metabolism. It implies that myo-inositol may improve survival by regulating energy or nutrient absorption. Additionally, the accelerated metamorphosis by myo-inositol may improve survival from megalopa to crablet of S. paramamosain. Overall, this study will provide the first insights into the underlying molecular mechanisms by which myo-inositol increases metamorphosis and survival.