Methylmercury: Reproductive and Behavioral Effects on Three Generations of Mallard Ducks

Abstract

Three generations of mallard ducks (Ana~ platyrh!lncllo. s! "-'ere fed either a control diet or a diet containing 0.5 ppm mercury in the form of methylmercury. The !~vel$ of men.-ury in adult tissues and eggs remained about the same over 3 generations. The methylmercury di~ had no effect on adult weights or weight changes during the reproductive season. Females fed a diet containin~ 0.5 ppm mercury laid a greater percentage of their eggs outside their nestboxes than did controls, and also laid fewer eggs and produced fewer ducklings. Methylmercury in .the diet appeared to result in a small amount of ~ggsh ell thinning. Ducklings from parents fed methylmercury were less responsive th;m controls to tape-recorde<i mat~mal calls, but were hyper-responsive to a fri~htenin£ stimulus in avoidance tests ; there were no significant differences in locomotor activity in an open-field test. The purpose of this paper is to describe reproductive and behavioral effects of methylmercury on 3 generations of mallard ducks. Findings for the 1st and 2nd generations were reported earlier (Heinz 1974, 1975, 1976b, 1976c, Heinz and Locke 1976). Here, I have combined the data for all 3 generations to determine changes from generation to generation and overall effects that might not have been statistically significant in the analysis of single generations. To my kno"\o•ledge, there have been no reported multiple generation studies on the effects of mercury or any other environmental pollutant on waterfowL Such studies have been reported for Japanese quail (Cotur-nix coturni:r japonica) (Carnio and McQueen 1973), ring-necked pheasants (Phasianus colchicus) {Dahlgren and Linder 1974), and ring doves (Streptopelia risoria) (Peakall et aL 1972). I thank the following people for their help in the study:

Rapidly increasing methyl mercury in endangered ivory gull ( Pagophila eburnea ) feathers over a 130 year record

“…The concentration of Hg in birds (as indicated by feather Hg) that causes deleterious effects, however, is subjected to numerous factors identified in the literature, including dietary composition, moult duration, phylogeny and ability to demethylate Hg in the liver [62][63][64]. In a review, Burger & Gochfeld [65] suggested that feather Hg between 5 and 40 mg g 21 dry weight rspb.royalsocietypublishing.org Proc.…”

Environmental contaminants in freshwater fish and their risk to piscivorous wildlife based on a national monitoring program

“…Consequently, the use of the most conservative TRVs may overestimate the actual risk of some contaminants to wildlife. For example, we initially used a TRV for mercury in bald eagle (0.0064 mg/kg/d) derived from a multi-generational study of mallards (Anas platyrychos ;Heinz 1979;Sample et al 1996). Based on this TRV, Yeardley et al (1998) estimated that mercury concentrations in fish from 98% of the lakes in the northeastern United States represented a risk to piscivorous birds.…”

Toxicity Reference Values and Tissue Residue Criteria for Protecting Avian Wildlife Exposed to Methylmercury in China

“…Thus, doses of 2 and 4 m g MeHg/g (dwt) were considered to be the dietary-based NOAEL and LOAEL values, respectively. However, both doses were greater than the LOAEL of 0.5 m g MeHg/g (dwt) (Heinz 1979 ) , which was determined from the results of a multigeneration exposure. The corresponding daily doses, which were converted from the dietary values using a rate of ingestion of food of 0.057 kg/kg (bm)/day, were 0.114 and 0.228 m g MeHg/g (bm)/day, respectively.…”

“…Based on multigenerational effects on reproduction, when converted from the dietary values by the use of rates of consumption of food of 0.156 kg food (wwt)/kg (bm)/day (US EPA 1995b ) , the dietary LOAEL value was 0.078 m g MeHg/g (bm)/day. Heinz ( 1974Heinz ( , 1975Heinz ( , 1976aHeinz ( , b, 1979 The corresponding concentrations of MeHg in tissues such as liver, kidney, breast muscle, brain, ovary, and primary feathers, and in eggs are given (geometric mean for three generations) for mallards (Heinz 1979 ; Table 2 ). Reproductive effects of MeHg on mallards were investigated by exposing adults to one of four doses of MeHg (1, 2, 4, or 8 m g MeHg/g (dwt)) (Heinz et al 2010a ) .…”