Study of routine metabolism and acute toxicity of mycogenic silver nanoparticles on Palaemon pandaliformis (shrimp)

Abstract

Palaemon pandaliformis is a shrimp species considered as an important indicator of environmental conditions. In this study, the toxicological effects of mycogenic silver nanoparticles obtained using the fungus Aspergillus tubingensis (AgNP-AT) were evaluated on P. pandaliformis. The AgNP-AT were spherical and homogeneous in size. Compared with the untreated group, at 10 μM AgNP-AT, there was a reduction of 60 and 87% for oxygen consumption and ammonia excretion, respectively. In addition to the untreated group, silver nitrate (AgNO₃) was also used as a control, where concentrations at least 10 times lower than those of the AgNPs also reduced the oxygen consumption by 54% and increased the ammonia excretion by 33%, demonstrating its high toxicity. At 24, 48, 72 and 96 h, the AgNP-AT showed lethal concentrations (LC₅₀) of 17.4, 14.4, 12.6 and 0.5 μM, while AgNO₃ showed LC₅₀ values of 2.5, 1.0, 0.02 and 0.01 μM, respectively. For all groups exposed to AgNPs, histological analysis showed that, in relation to the untreated group, there was a significant increase in the mean area of the shrimps' gills, indicating hypertrophy. All the changes observed in the hepatopancreatic and gill tissue, mainly for AgNPs at the highest concentration of 10 μM, are described as reversible. The results indicated that the AgNP-AT toxicity to the shrimps increased according to the time of exposure. However, it is important to highlight that the AgNP-AT were less toxic than AgNO₃ to the shrimps, probably due to the presence of a protein coat in these AgNPs, which is able to control the release of Ag⁺ ions, avoiding high toxicity to the shrimps.