Effect of nonylphenol on giant freshwater prawn ( Macrobrachium rosenbergii) via oral treatment: Toxicity and messenger RNA expression of hemocyte genes

Abstract

A previous in vitro study has indicated that two alkylphenol ethoxylates (APEs) could potentially damage hemocytes and influence cellular immunity of prawns ( Macrobrachium rosenbergii). The aim of this study was to investigate the effects of nonylphenol (NP) on susceptibility to a pathogen and on the mRNA expression of hemocyte genes, including four immune-related genes. NP at different concentrations was fed continuously to prawn ( M. rosenbergii) for 1, 3, 6, and 9 days. Challenging prawns with Lactobacillus garvieae resulted in 44–50%, 20–24% and 10–12% mortality were detected after prawns were fed with 100, 10 and 1 μg of NP/prawn for 6 days, respectively. In comparison with control prawns fed with phosphate-buffered solution (PBS), the increase of mRNA levels of four immune-related genes, alpha-2 microglobulin ( α-2m), antimicrobial peptides ( amp), peroxinectin ( pon), and prophenoloxidase ( propo), was detected on days 1, 3 and 6 after feeding with 100 μg/prawn; on day 9, only the mRNA level of amp of the NP-treated group was significantly increased, while that of the remaining groups was not different from that of the control. In addition, two other hemocyte genes were also studied, including a respiration-related gene, cytochrome oxidase subunit ( cos), and an unknown gene, L12X3. The mRNA level of cos was elevated during the experimental period, but an increase of L12X3 expression was detected only on day 1 after treatment. Regarding sensitivity of these genes to NP, the results from NP-treated prawns on day 1 after treatment revealed (1) that mRNA expression of the six genes in the 100-μg-NP-treated group was significantly different from that of control group, (2) that the mRNA levels of three immune-related genes ( amp, pon and propo) in 10-μg-treated group were significantly higher than that of control group, and (3) that a significant change of propo was detected in 1-μg-treated group. These results suggest that NP may enhance the immune response of prawns, but the effect created by a high concentration of NP may damage prawns, and then increase the susceptibility to pathogen.