Effects of cadmium, mercury, and selenium on reproductive indices in male lesser scaup (Aythya affinis) in the western Boreal forest.
Combined lesser scaup (Aythya affinis) and greater scaup (A. marila) populations decreased from the 1980s to the 1990s and have not recovered. Factors limiting reproduction, including effects of contaminants and trace elements, have been highlighted as a concern in female scaup, but no studies have examined possible effects on male scaup. We examined the effects of cadmium, mercury, selenium, and corticosterone on pair status and on male reproductive indices, including testosterone, testes mass, and seminiferous tubule diameter, in male lesser scaup collected in the western boreal forest near Yellowknife, Northwest Territories, May and June, during 2004 and 2005. Male scaup that were larger in size (p = 0.048) and with better body condition (p = 0.038) were more likely to be paired. No relations were observed between independent variables and testosterone and testes mass. However, results suggested that seminiferous tubule diameter is influenced by a complex array of biologic and toxicologic parameters, which differ depending on pair status. Tubule diameters of paired male scaup were negatively influenced by hormones, whereas contaminants influenced diameter in unpaired male scaup. The effects of selenium were attenuated when bound with cadmium but not mercury. When selenium concentrations were high (greater than median value), there was a positive effect of cadmium on tubule diameter (R(2) = 0.30, n = 10, p = 0.007) but a negative relation with mercury (R(2) = 0.15, n = 10, p = 0.09). Seminiferous tubule diameter may be a sensitive indicator of sublethal effects of contaminants. This study showed contaminant and trace element effects at concentrations lower than threshold levels associated with major toxic effects. This study also demonstrated the complex nature of biologic systems and the importance of considering interactions to accurately characterize effects of metals.
Pollock
B
B
Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, S7N 5B4, Saskatchewan, Saskatoon, Canada.
Machin
K L
KL
D000818:Animals; D002104:Cadmium / Q000633:toxicity; D002170:Canada; D003345:Corticosterone / Q000097:blood; D004372:Ducks; D004781:Environmental Exposure / Q000009:adverse effects*; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000032:analysis / Q000378:metabolism / Q000633:toxicity*; D007668:Kidney / Q000737:chemistry / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008297:Male; D008628:Mercury / Q000633:toxicity; D019216:Metals, Heavy / Q000032:analysis / Q000378:metabolism / Q000633:toxicity*; D009929:Organ Size / Q000187:drug effects; D012098:Reproduction / Q000187:drug effects* / Q000502:physiology; D012643:Selenium / Q000633:toxicity; D012671:Seminiferous Tubules / Q000187:drug effects / Q000473:pathology; D012726:Sexual Behavior, Animal / Q000187:drug effects / Q000502:physiology; D013737:Testis / Q000187:drug effects / Q000473:pathology; D013739:Testosterone / Q000097:blood; D014197:Trees
D004785:Environmental Pollutants; D019216:Metals, Heavy; D002104:Cadmium; D013739:Testosterone; D008628:Mercury; D012643:Selenium; D003345:Corticosterone