Papillae growth and molecular responses in sea cucumber (Apostichopus japonicus) exposed to light spectra

This study primarily investigated the light spectra that increased the number of papillae in sea cucumbers and the molecular pathways that contributed to the growth of papillae under these light conditions. At 8.0-15.0 °C, sea cucumbers were subjected to a 60-day indoor experiment under different lighting environments (normal, dark, blue light, yellow light, green light, red light, and white light). The number of papillae was analyzed using repeated measures ANOVA, and transcriptome sequencing data of the papillae were subsequently analyzed. The analysis revealed that there were significant differences in the number of papillae within each group at the beginning of the experiment and on days 15, 30, and 45 of light exposure (p < 0.05), while no significant differences were observed within each group between days 45 and 60 of light exposure (p > 0.05). Under blue light exposure, the number of papillae and the increase in the number of papillae in sea cucumbers showed significant differences compared to the control group (p < 0.05). The pathways related to the increase in the number of papillae in sea cucumbers include phenylalanine, tyrosine, and tryptophan biosynthesis and phenylalanine metabolism. The number of papillae increased the most after 45 days of blue light exposure, after which it stabilized. It was speculated that the increase in the number of papillae might be related to amino acid metabolism and collagen synthesis.