Interrelationship of salinity shift with oxidative stress and lipid metabolism in the monogonont rotifer Brachionus koreanus

Salinity is a critical key abiotic factor affecting biological processes such as lipid metabolism, yet the relationship between salinity and lipid metabolism has not been studied in the rotifer. To understand the effects of salinity on the monogonont rotifer B. koreanus, we examined high saline (25 and 35 psu) conditions compared to the control (15 psu). In vivo life cycle parameters (e.g. cumulative offspring and life span) were observed in response to 25 and 35 psu compared to 15 psu. In addition, to investigate whether high salinity induces oxidative stress, the level of reactive oxygen species (ROS) and glutathione S-transferase activity (GST) were measured in a salinity- (15, 25, and 35 psu; 24 h) and time-dependent manner (3, 6, 12, 24 h; 35 psu). Furthermore composition of fatty acid (FA) and lipid metabolism-related genes (e.g. elongases and desaturases) were examined in response to different salinity conditions. As a result, retardation in cumulative offspring and significant increase in life span were demonstrated in the 35 psu treatment group compared to the control (15 psu). Furthermore, ROS level and GST activity have both demonstrated a significant increase (P < 0.05) in the 35 psu treatment. In general, the quantity of FA and mRNA expression of the lipid metabolism-related genes was significantly decreased (P < 0.05) in response to high saline condition with exceptions for both GST-S4 and S5 demonstrated a significant increase in their mRNA expression. This study demonstrates that high salinity induces oxidative stress, leading to a negative impact on lipid metabolism in the monogonont rotifer, B. koreanus.