Bosmina fatalis adapting to ammonia through oxidative stress and ribosome increase

Abstract

Ammonia is generated in large quantities during organic degradation, concluding that of cyanobacteria, which is toxic to aquatic animals. B. fatalis is a widespread cladoceran species found in freshwater. The present study aimed to explore the toxic responses of B. fatalis to ammonia. Our experiments showed that the 24, 48, 72 and 96 h LC50 values of NH3 on B. fatalis were 20.59, 13.06, 5.77 and 3.36 mg·L−1, respectively. A 14-days NH3 exposure study at 0, 0.22, 0.57 and 1.4 mg·L−1 were carried out. NH3 at low and medium doses (0.22 and 0.57 mg·L−1) displayed stimulative effects on the B. fatalis population and the body length of the newborns, while NH3 at high dose (1.4 mg·L−1) did not exhibit significant effect on the B. fatalis population and size. Transmission electron microscope (TEM) revealed significant increase in number of ribosomes at low doses, while the interior structure showed no marked change at high dose. The levels of indicators related to oxidative stress (ACP, SOD, CAT, GSH-Px and MDA) caused by NH3 first increasedand, then decreased with time in all the NH3-exposure groups. The mRNA expression of genes related to ribosomal structure (RPL12, RPL10, RPL10A, RPL27A and RPL19) and antioxidant stress (CAT, SOD and GSH-Px) was rapidly downregulated after NH3 exposure. Collectively, it is inferred that ammonia at a certain dose (≤0.57 mg·L−1) stimulates the growth and reproduction of B. fatalis, which may be its defensive reaction to ammonia.

Keywords

• bosmina fatalis
• ammonia
• growth performance
• ribosome antioxidant responses