Three generations of mallard ducks (Anas platyrhynchos) were fed either a control diet or a diet containing 0.5 ppm mercury in the form of methylmercury. The levels of mercury in adult tissues and eggs remained about the same over 3 generations. The methylmercury diet had no effect on adult weights or weight changes during the reproductive season. Females fed a diet containing 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 eggshell thinning. Ducklings from parents fed methylmercury were less responsive than controls to tape-recorded maternal calls, but were hyper-responsive to a frightening stimulus in avoidance tests; there were no significant differences in locomotor activity in an open-field test. J. WILDL. MANAGE. 43(2):394-401 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 knowledge, 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 (Coturnix coturnix 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: C. S. Cruger, R. B. Frederick, D. C. Gray, R. G. Heath, P. A. Heinz, G. Hensler, and N. C. Miller. J. B. Elder provided the Morsodren used in this study and others. METHODS An abbreviated description of the care of adults, care of eggs and young, and behavioral tests is given below. Additional details were reported previously (Heinz 1974, 1976b, 1976c). A 1-way analysis of variance was used to check for changes in mercury levels in tissues from generation to generation. Reproductive and behavioral comparisons involved 2 factors (treatment and generation); these comparisons were made with a 2-way analysis of variance. A significance level of 0.05 was used. Generation effects are not discussed because significant differences from 1 year to another, if any, would not be related to mercury treatment but to other factors such as weather.

https://www.jstor.org/stable/pdfplus/3800348.pdf

Methylmercury: Reproductive and behavioral effects on three generations of mallard ducks

Captive great egret (Ardea albus) nestlings were maintained as controls or were dosed with methylmercury chloride at low (0.5), and high doses (5 mg/kg, wet weight) in fish. Low dosed birds were given methylmercury at concentrations comparable to current exposure of wild birds in the Everglades (Florida, USA). When compared with controls, low dosed birds had lower packed cell volumes, dingy feathers, increased lymphocytic cuffing in a skin test, increased bone marrow cellularity, decreased bursal wall thickness, decreased thymic lobule size, fewer lymphoid aggregates in lung, increased perivascular edema in lung, and decreased phagocytized carbon in lung. High dosed birds became severely ataxic and had severe hematologic, neurologic, and histologic changes. The most severe lesions were in immune and nervous system tissues. By comparing responses in captive and wild birds, we found that sublethal effects of mercury were detected at lower levels in captive than in wild birds, probably due to the reduced sources of variation characteristic of the highly controlled laboratory study. Conversely, thresholds for more severe changes (death, disease) occurred at lower concentrations in wild birds than in captive birds, probably because wild birds were exposed to multiple stressors. Thus caution should be used in applying lowest observed effect levels between captive and wild studies.

https://bioone.org/journals/journal-of-wildlife-diseases/volume-36/issue-3/0090-3558-36.3.423/HISTOLOGIC-NEUROLOGIC-AND-IMMUNOLOGIC-EFFECTS-OF-METHYLMERCURY-IN-CAPTIVE-GREAT/10.7589/0090-3558-36.3.423.pdf

Histologic, neurologic, and immunologic effects of methylmercury in captive great egrets

Pregnant rats were given various doses of methylmercury (MM) at three different stages of gestation (Days 0, 7 or 14). Administration of 56% or 27% of the dose given on the first day (Day 0) of pregnancy to 7 or 14 day pregnant rats, respectively, resulted in equivalent concentrations of MM ni 19 day old feti and 1 day and 1 week old neonates. A single, 5 mg MM/kg, oral dose on Day 0, or its equivalent on Days 7 or 14 of gestation did not produce any signs of toxicity in pregnant dams or their offspring. Weight gain of pregnant dams, litter size, litter weights at birth or at weaning and gross physical appearance were not different amongst the various treated groups and their respective controls. Operant level of bar pressing and acquisition of a discrete trial autoshape task indicated no differences with respect to operant levels, rate of acquisition or asymptotic performance resulting from exposure to MM in utero. The operant (autoshaped) behavior showed sex related differences to the disrupting influence of d-amphetamine (d-A); females were significantly more sensitive than males. Moreover, both males and females whose dams were treated with MM on Day 0 or 7 of pregnancy were significantly less affected by the d-A when compared with controls. Offspring born to dams given MM on Day 14 of pregnancy did not show a differential effect of d-A. It is concluded that early prenatal exposure to low doses of MM can result in behavioral consequences subtle enough to require unmasking of the effects with psychotropic drugs. Additionally, periods may exist during development when the embryo or fetus is most susceptible to behavioral or functional teratogenic effects of exposure to chemical insult. The testing procedures used in these experiments were objective, automatic and amenable for use with relatively large sample sizes compared with other operant behavior analytical methods. They also lend themselves to appropriate parametric statistical analyses, a staunch requirement for behavioral toxicological and teratological studies.

d-Amphetamine unmasks postnatal consequences of exposure to methylmercury in utero: methods for studying behavioral teratogenesis.

BACKGROUND: Cells respond to adverse environmental stimuli by enhancing the expression of specific genes, the products of which include a suite of proteins known as heat shock proteins (hsps), a response often attributed to cellular protection. METHODS:In this study, we characterized alterations in hsp expression in chick embryos (Hamburger-Hamilton stage 17, 72 h) exposed in ovo to arsenite (As), mercury (Hg), and cadmium (Cd), known developmental toxicants. Embryos were incubated for 2 h following exposure to 3, 10, 30, or 100 nmol metal, or for 2, 4, 12, or 24 h following treatment with 10 nmol metal. RESULTS: An enhanced de novo synthesis of 24-, 70-, and 90-kD, 70- and 90-kD, and 70-kD proteins was observed with As, Hg, and Cd treatments, respectively. These responses were transient; apparent rates of protein synthesis were maximal 2–4 h after exposure and returned to control rates by 24 h. Actinomycin D experiments demonstrated that arsenite-induced expression of these proteins is transcriptionally regulated. Immunoblotting experiments identified the 24-, 70-, and 90-kD proteins as the heat shock proteins hsp24, hsp70, and hsp90, respectively. Exposure duration-related abnormalities were noted in the neural tube with all metals and in the ganglia and somites with Cd and As. Retina, allantois, and limb defects were specific to Cd-treated embryos, and branchial arch defects were specific to As-treated embryos. CONCLUSIONS: The data support metal-induced developmental abnormalities, which are preceded by synthesis of stress proteins. Birth Defects Res B 68:456–464, 2003. Published 2003 Wiley-Liss, Inc.

Mercury, cadmium, and arsenite enhance heat shock protein synthesis in chick embryos prior to embryotoxicity.

At a symposium, which has been considered as a landmark in environmental concerns, held at the Institute for Terrestrial Ecology in 1965 the following statements on behavioral toxicology were made (Warner et al. 1966): 

(1)

“The behavior (or activities) of an organism represents the final integrated result of a diversity of biochemical and physiological processes. Thus, a single behavioral parameter is generally more comprehensive than a physiological or biochemical parameter.




(2)

Behavioral patterns are known to be highly sensitive to changes in the steady state of an organism. This sensitivity is one of the key values for its use in exploring sublethal toxicity.




(3)

Behavioral measurements can usually be made without direct physical harm to the organism. With aquatic animals especially, implantation of detectors introduces problems of considerable complexity. Behavioral measurements can avoid this difficulty.”

Behavioral responses of birds to pesticides and other contaminants

Methylmercury dicyandiamide (0.05 to 10 mg/kg egg) injected into the yolk sac of fertilized chicken eggs prior to incubation produced a dose related decrease in the percentage of chicks hatched (90-57% of control). With dosage fixed at 0.5 or 5.0 mg/kg egg and injections made on Days 0, 7 or 14 of incubation, hatches were 90, 68 and 75%, respectively, for the low dose and 63, 13 and 18% for the high dose. In contrast to results obtained from chicks hatched from eggs injected on Day 0 of incubation, chicks hatched from eggs injected with 0.5 or 5.0 mg MMD/kg on Day 7 or 14 were not different from controls in a detour learning situation. Administration of 14-C methylmercury revealed maximal brain radiolabel in embryos injected on Day 0 to be 10% that seen with eggs injected on Day 7 but twice that seen with eggs injected on Day 14. We tentatively conclude that a period of maximal sensitivity to the behavior effects exists prior to Day 7 and that the mechanisms of embryolethality is different from that producing the functional deficits.

E. Rosenthal

Papers

Time dependent effects produced in chicks after prenatal injection of methylmercury