Sex and low-level sampling stress modify the impacts of sewage effluent on the rainbow trout (Oncorhynchus mykiss) immune system

Abstract

The objective of the present study was to investigate the influence of chronic exposure to municipal sewage treatment effluent at environmentally relevant concentrations on immune parameters in rainbow trout (Oncorhynchus mykiss), including the assessment of potential differences in reactivity between sexually mature male and female fish. Trout were exposed to 1.5 and 15% (v/v) secondary treated municipal sewage effluent for 32 weeks. Fish were injected intra-peritoneally either with inactivated Aeromonas salmonicida to simulate an infection or with PBS as control for this immune challenge 6 weeks prior to sampling. Exposure to effluent resulted in a decrease in A. salmonicida-specific serum antibody level and blood lymphocyte numbers in mature females, but not in male fish. Injection of A. salmonicida resulted in enhanced serum lysozyme activity in mature male trout, which were not exposed to effluent. This stimulating effect of A. salmonicida could not be found in effluent-exposed trout, again potentially revealing a suppressive effect of the effluent. An influence of sampling fish on two consecutive days was observed in many immune parameters, most likely reflecting handling stress. Leucocyte and lymphocyte numbers in peripheral blood were consistently lower in male and female fish on the second sampling day. Phagocytosis in head kidney macrophages from male trout was also influenced by sampling day, whereby a stimulation of this reaction occurred on the second day of sampling. Liver mixed function oxygenase activity was found to be enhanced in mature male trout exposed to 15% effluent. In conclusion, the study showed, that exposure to sewage treatment plant effluent, in surface water relevant concentrations, can lead to potentially adverse effects on selected immune reactions in rainbow trout. However, this study also demonstrated that both handling stress and the sex of mature fish have distinct influences on the immune response detected in male and female fish and are likely to influence measured immune parameters to the extent that subtle effluent induced changes may be difficult to detect.

Stimulation of reproductive growth in rainbow trout (Oncorhynchus mykiss) following exposure to treated sewage effluent

“…Immune endpoints examined in the same rainbow trout sampled in this paper showed a constant unspecific stimulation of different leucoeyte populations in immune organs reminiscent of chronic inflammation [34]. Decreases in serum lysozyme und circulating lymphocytes were also observed only in female trout from this experiment [32].…”

“…As the exposed fish were on eontrolled 1'atio118 and physiological data such as condition faetor 01' growth did not show other indications of increases in ene1'gy storage, it is difficult to attribute this change to inereased energy storage in the liver. Thus, it is more likely that the increased liver size is due to increased biosynthesis in the liver, related in part to reproductive functions as well as eontaminant rnetabolism, such as 7-ethoxyresorufin-O-decthyluse activity, which was induced in male trout exposed to 15% ef:fluent [32].…”

Evidence of impaired health in yellow perch (Perca flavescens) from a biological mercury hotspot in northeastern north America

“…We found, however, that the relative area occupied by MAs in both the liver and kidney of male perch was higher than that in the females at similar THg concentrations. The MAs are known to be involved in immune function, particularly antigen recognition [19], and the immune response of fish can differ between sexes following contaminant exposure (e.g., [36]). This could explain the sex differences we found; however, the effects of MeHg on fish immune function are not well understood [30].…”

The effects of treated effluents on the intensity of papillomatosis and HSP70 expression in roach

“…Aaltonen et al (2000) exposed roach to primary and secondary treated kraft mill effluents in laboratory and noticed that inhibitory effect for immunity was more obvious in male than female roach. Also in rainbow trout (Oncorhynchus mykiss) and carp (Cyprinius carpio L.) immunity responses were suppressed when exposed to sewage effluents (Hoeger, et al 2005;Price, et al 1997), and interestingly female rainbow trout experienced more severe immunosuppression than males (Hoeger, et al 2005). Endrocrine disrupting substances in the effluent can also affect by suppressing immunity of fish (Savino and Dardenne 1995;Watanuki, et al 2002).…”