Mercury levels in avian feathers from different trophic levels of eight families collected from the northern region of Iran.

Mercury levels were determined in feathers from 83 birds belonging to 18 species (eight families), all collected from the northern region of Iran. Mercury levels were evaluated in relation to taxonomic affiliation and feeding strategies. Mercury levels in the feathers were between 0.05 ± 0.01 and 1.10 ± 0.15 µg g(-1) dry weight, and there was a significant effect of taxonomic groups (p < 0.05). The highest mercury levels were found in Accipitridae, and mercury was not detected in the family Upupidae. The pattern for mercury levels was Accipitridae > Pelecanidae > Sternidae > Ardeidae > Anatidae > Rallidae > Phasianidae (p < 0.05). Significant differences (p < 0.05) in the mean mercury levels were found among species as a function of feeding method and trophic level. Mercury levels were highest in the carnivorous species and lowest in the herbivorous species. Mercury levels in feathers of birds in this study were generally below the thresholds reported to affect reproduction.

Short-term responses of selected endocrine parameters in juvenile rainbow trout (Oncorhynchus mykiss) exposed to 4-nonylphenol.

The synthetic organic compound 4-nonylphenol (4-NP) has been shown to have a wide range of adverse effects on the endocrine system of various animals including fish. The present study evaluated the potential effects of 4-NP on vitellogenin (VTG) synthesis, steroid, and thyroid hormone concentrations in both juvenile male and female rainbow trout (Oncorhynchus mykiss). Fish were exposed by intraperitoneal injection to different doses of 4-NP (1, 10, 50, and 100 µg g(-1)) or vehicle (coconut oil) over a period of 14 days. Blood samples were collected 7 and 14 days after initiation of treatment. Plasma VTG levels in 4-NP-treated fish were detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis as a high molecular weight protein band of 180 KDa. In addition, plasma VTG concentrations were quantified indirectly using plasma alkali-labile phosphate (ALP) and plasma calcium. Both ALP and calcium levels in plasma showed similar and parallel increase patterns after exposure to 4-NP that were significantly higher compared with controls. The analysis of plasma sex steroid levels revealed a significant increase in 17ß-estradiol and testosterone in plasma of juvenile males and females, respectively. Furthermore, a significant increase was observed in plasma cortisol levels. On the other hand, 4-NP decreased both plasma triiodothyronine and thyroxine after 7 and 14 days of treatment. These results suggest that 4-NP can affect different parts of the endocrine system, which may lead to serious impairments in physiological homeostasis of juvenile rainbow trout.