P ART 3 Lethal and Sublethal Effects of Mercury under Controlled Conditions © 2006 by Taylor & Francis Group, LLC 155 C HAPTER 8 Lethal Effects of Mercury This chapter synthesizes available literature on the lethality of inorganic and organic mercury compounds to freshwater and marine biota; the effect of route of administration of various mer- curials on the survival of representative species of waterfowl, passerines, raptors, and other avian groups; and the lethality of organomercury compounds to humans, small laboratory mammals, livestock, domestic cats and dogs, and various species of wildlife. Death is the only biological variable now measured that is considered irreversible by all investigators. Nevertheless, time of death is modified by a host of physical, chemical, biological, metabolic, and behavioral variables, and it is unfortunate that some regulatory agencies still set mercury criteria to protect natural resources and human health on the basis of death — usually concentrations producing 50.0% mortality — and some variable uncertainty factor. Mercury criteria for protection of natural resources and human health, as discussed in Chapter 12, should be based — at a minimum — on the highest dose tested or highest tissue concentration found that does not produce death, impaired reproduction, inhibited growth, or disrupted well-being. 8.1 AQUATIC ORGANISMS Lethal concentrations of mercury salts ranged from less than 0.1 µg Hg/L to more than 200.0 µg/L for representative sensitive species of marine and freshwater organisms (Table 8.1). The lower concentrations of less than 2.0 µg/L recorded were usually associated with early developmental stages, long exposures, and flowthrough tests (Table 8.1). Among teleosts, females and larger fish were more resistant to lethal effects of mercury than were males and smaller fishes (Diamond et al., 1989). Among metals tested, mercury was the most toxic to aquatic organisms, and organomercury compounds showed the greatest biocidal potential (Eisler, 1981; Jayaprakash and Madhyastha, 1987). In general, mercury toxicity was higher at elevated temperatures (Armstrong, 1979), at reduced salinities for marine organisms (McKenney and Costlow, 1981), and in the presence of other metals such as zinc and lead (Parker, 1979). Salinity stress, for example, especially abnormally low salinities, reduced significantly the survival time of mercury-exposed isopod crustaceans (Jones, 1973), suggesting that species adapted to a fluctuating marine environment — typical of the intertidal zone — could be more vulnerable to the added stress of mercury than species inhabiting more uniformly stable environments. 8.1.1 Invertebrates The marine ciliate protozoan Uronema marinum, with an LC50 (24 h) value of 6.0 µg/L, failed to develop resistance to mercury over an 18-week period (Parker, 1979). However, another marine © 2006 by Taylor & Francis Group, LLC © 2006 by Taylor & Francis Group, LLC 156 MERCURY HAZARDS TO LIVING ORGANISMS Table 8.1 Lethality of Inorganic and Organic Mercury Compounds to Selected Species of Aquatic Organisms Chemical Species, Ecosystem, Taxonomic Group, Species, and Other Variables Concentration ( µµ µµ g Hg/L medium) Effect a Ref. b Inorganic Mercury: Freshwater Crustaceans Crayfish, Orconectes limosus 2.0 LC50 (30 d) 1 Daphnid Daphnia magna 5.0 LC50 (96 h) 1 Daphnid, Daphnia magna 1.3–1.8 LC50 (LT) 1 Scud, Gammarus pseudolimnaeus 10.0 LC50 (96 h) 1 Molluscs Rainbow mussel, Villosa iris: Glochidia 14.0 LC50 (72 h) 33 Glochidia 25.5 All dead in 72 h 33 Juveniles; age 2 months; not fed during exposure 99.0 LC50 (96 h) 33 Juveniles; age 2 months; not fed during exposure 234.0 All dead in 96 h 33 Juveniles; age 2 months; fed 114.0 None dead in 21 d 33 Fish Zebrafish, Brachydanio rerio ; embryo-larvae < 2.0 No deaths 16 Goldfish, Carassius auratus 122.0 LC50 (96 h) 27 Air-breathing catfish, Clarias batrachus ; adults 507.0 LC50 (96 h) 18 Catfish, Clarias lazera: Adults 720.0 LC50 (96 h) 17 Adults 960.0 LC50 (24 h) 17 Mosquitofish, Gambusia affinis ; adults 1000.0 LC77 (10 d) 19 Channel catfish, Ictalurus punctatus ; embryo- larva: Static test 30.0 LC50 (10 d) 2 Flowthrough test 0.3 LC50 (10 d) 2 Largemouth bass, Micropterus salmoides ; embryo-larva: Static test 188.0 (138.0–238.0) LC50 (8 d) 2, 27 Flowthrough test 5.3 LC50 (8 d) 2 Rainbow trout, Oncorhynchus mykiss : Juveniles 155.0–200.0 LC50 (96 h) 1 Embryo-larva: Static test 4.7 (4.2–5.3) LC50 (28 d) 2, 27 Flowthrough test < 0.1 LC50 (28 d) 2 Subadults 64.0 LC50 (58 d) 20 Subadults 426.0 LC50 (24 h) 20 Brook trout, Salvelinus fontinalis 0.3–0.9 LC50 (LT) 1 Tench, Tinca tinca 1000.0 All dead in 48 h 26 Tench 100.0 None dead in 3 weeks 26 Bronze featherback, Notopterus notopterus 440.0 LC50 (96h) 3 Amphibians Blanchard’s cricket frog, Acris crepitans blanchardi ; embryo-larva 10.0 (8.5–13.0) LC50 (72 h) 27 Kentucky small-mouthed salamander, Ambystoma barbouri ; embryo-larva 8.0 (2.0–14.0) LC50 (168–192 h) 27 Jefferson’s salamander, Ambystoma jeffersonianum ; embryo-larva 19.0 (16.0–21.0) LC50 (144–192 h) 27 © 2006 by Taylor & Francis Group, LLC LETHAL EFFECTS OF MERCURY 157 Table 8.1 (continued) Lethality of Inorganic and Organic Mercury Compounds to Selected Species of Aquatic Organisms Chemical Species, Ecosystem, Taxonomic Group, Species, and Other Variables Concentration ( µµ µµ g Hg/L medium) Effect a Ref. b Spotted salamander, Ambystoma maculatum ; embryo-larva 31.0 (25.0–37.0) LC50 (144–168 h) 27 Marbled salamander, Ambystoma opacum ; embryo-larva 103.0 (63.0–153.0) LC50 (120–144 h) 27 Small-mouthed salamander, Ambystoma texanum 27.0 (21.0–33.0) LC50 (144–168 h) 27 Anurans; 4 spp; embryo-larva 36.8–67.2 LC50 (96 h) 2 Eastern green toad, Bufo debilis debilis ; embryo-larva 40.0 (26.0–52.0) LC50 (72 h) 27 Fowler’s toad, Bufo woodhousei fowlerei: Embryo-larva 35.0 (21.0–38.0) LC50 (72 h) 27 Tadpole 25 LC50 (72 h) 28 Toad, Bufo melanosticus ; tadpole 185 LC50 (96 h) 28 Red-spotted toad, Bufo punctatus ; embryo- larva 32.0 (22.0–41.0) LC50 (72 h) 27 Narrow-mouthed toad, Gastrophryne carolinensis ; embryo-larva 1.0 (0.9–1.9) LC50 (72 h) 27 Southern gray treefrog, Hyla chrysoscelis ; embryo-larva 2.3 (1.5–3.4) LC50 (72 h) 27 Treefrogs, Hyla spp.; embryo-larva; 5 species 2.4–2.8 LC50 (72–96 h) 2, 27 Frog, Microhyla ornata ; tadpoles: Embryo 126.0 LC50 (96 h) 29 Tadpoles: Recently-metamorphosed 88.0 LC50 (96 h) 29 Age 1 week 1120.0 LC50 (96 h) 13, 30 Age 4 weeks 1430.0 LC50 (96 h) 13, 30 Spring peeper, Pseudocris crucifer ; embryo- larva 2.3 (0.3–4.9) LC50 (72 h) 27 Frog, Rana breviceps ; tadpole 207.0 LC50 (96 h) 28 Bullfrog, Rana catesbeina ; embryo-larva 6.3 (4.9–8.1) LC50 (144–192 h) 27 Frog, Rana cyanophlyctis : Adult females 960.0 LC50 (31–65 d) 14 Adult females 4800.0 LC50 (96 h) 14 Pig frog, Rana grylio ; embryo-larva 59.0 (32.0–109.0) LC50 (144–192 h) 27 River frog, Rana heckscheri: Embryo-larva 55.0 (38.0–78.0) LC50 (72 h) 27 Embryo 502.0 LC50 (96 h) 31 Adults 3252.0 LC50 (96 h) 31 Adult females 880.0 No deaths in 60 d 15 Adult females 4400.0 LC50 (96 h) 15 Pickerel frog, Rana palustris ; embryo-larva 5.1 (4.0–6.2) LC50 (144 h) 27 Leopard frog, Rana pipens ; embryo-larva 7.3 LC50 (96 h) 2 Northern leopard frog, Rana pipiens pipiens ; embryo-larva 8.4 (5.3–13.3) LC50 (144 h) 27 Southern leopard frog, Rana sphenocephala ; tadpoles; fed diets containing various concentrations of HgCl 2 for 254 d: Control 0.0 mg/kg FW diet 12.0% dead in 240 d 34 Low Hg diet 0.1 mg Hg/kg FW diet None dead in 240 d 34 Medium Hg diet 0.5 mg Hg/kg FW diet 22.0% dead in 70 d; 28.0% dead in 240 d 34 High Hg diet 1.0 mg Hg/kg FW diet 28.0% dead in 240 d South African clawed frog, Xenopus laevis ; tadpole 74.0 LC50 (48 h) 32 (continued) © 2006 by Taylor & Francis Group, LLC 158 MERCURY HAZARDS TO LIVING ORGANISMS Table 8.1 (continued) Lethality of Inorganic and Organic Mercury Compounds to Selected Species of Aquatic Organisms Chemical Species, Ecosystem, Taxonomic Group, Species, and Other Variables Concentration ( µµ µµ g Hg/L medium) Effect a Ref. b Inorganic Mercury: Marine Protozoans Ciliate, Uronema marinum 6.0 LC50 (24 h) 4 Coelenterates Coral, Porites asteroides: Colonies 100.0, nominal; 37.0, measured No deaths in 15 d 25 Colonies 500.0 (nominal); 180.0 (measured) 3 of 6 colonies dead in 72 h; remaining 3 colonies survived exposure for at least 15 d 25 Molluscs Softshell clam, Mya arenaria : Adults 1.0 No deaths in 168 h 5 Adults 4.0 LC50 (168 h) 5 Adults 30.0 All dead in 168 h 5 Adults 400.0 LC50 (96 h) 5 Hardshell clam, Mercenaria mercenaria : Larva 4.8 LC50 (48 h) 1 Larva 4.0 LC50 (9 d) 1 American oyster, Crassostrea virginica : Embryo 3.3 5.0% dead in 12 d 1 Larva 5.6 LC50 (48 h) 1 Adult 5.5–10.2 LC50 (48 h) 1 Pacific oyster, Crassostrea gigas ; embryos 5.7 LC50 (48 h) 10 Common mussel, Mytilus edulis 5.8 LC50 (96 h) 6 Mud snail, Nassarius obsoletus : Adults 100.0 No deaths in 168 h 5 Adults 700.0 LC 50 (168 h) 5 Adults 5000.0 LC (100 (168 h) 5 Adults 32,000.0 LC 50 (96 h) 5 Slipper limpet, Crepidula fornicata : Larva 60.0 LC50 (96 h) 7 Adults 330.0 LC50 (96 h) 7 Bay scallop, Argopecten irradians ; juveniles 89.0 LC50 (96 h) 8 Crustaceans Fiddler crab, Uca pugilator , zoea 1.8 LC50 (8 d) 1 Mysid shrimp, Mysidopsis bahia : Juveniles 3.5 LC50 (96 h) 9 Egg to egg exposure 1.8 LC50 (LT) 9 Dungeness crab, Cancer magister ; larva 6.6 LC50 (96 h) 10 Copepod, Acartia tonsa ; adult 10.0–15.0 LC50 (96 h) 1 Hermit crab, Pagurus longicarpus : Adults 10.0 No deaths in 168 h 5 Adults 50.0 LC50 (96 h) 5 Adults 50.0 LC50 (168 h) 5 Adults 125.0 All dead in 168 h 5 Prawn, Penaeus indicus : Postlarva 16.1 LC50 (48 h) 11 Postlarva 15.3 LC50 (96 h) 11 © 2006 by Taylor & Francis Group, LLC LETHAL EFFECTS OF MERCURY 159 Table 8.1 (continued) Lethality of Inorganic and Organic Mercury Compounds to Selected Species of Aquatic Organisms Chemical Species, Ecosystem, Taxonomic Group, Species, and Other Variables Concentration ( µµ µµ g Hg/L medium) Effect a Ref. b Annelids Polychaete, Capitella capitata ; larva 14.0 LC50 (96 h) 1 Sandworm, Nereis virens: Adults 25.0 No deaths in 168 h 5 Adults 60.0 LC50 (168 h) 5 Adults 70.0 LC50 (96 h) 5 Adults 125.0 All dead in 168 h 5 Echinoderms Starfish, Asterias rubens: Adults 10.0 No deaths in 168 h 5 Adults 20.0 LC50 (168 h) 5 Adults 60.0 LC50 (96 h) 5 Adults 125.0 All dead in 168 h 5 Fish Haddock, Melanogrammus aeglefinus; larvae 98.0 LC50 (96 h) 1 Spot, Leiostomus xanthurus; adult 36.0 (32.0–39.0) LC50 (96 h) 23 Tidewater silverside, Menidia peninsulae; larvae, age 26 days 71.0 (60.0–84.0) LC50 (96 h) 23 Mummichog, Fundulus heteroclitus: Adults 80.0 LC50 (96 h) 5 Adults 80.0 LC50 (168 h) 5 Adults 23,000.0 LC50 (24 h) 5 Organic Mercury: Freshwater Planarians Flatworm, Dugesia dorotocephala: Adult 200.0 LC0 (10 d) 12 Adult 500.0 LC100 (5 d) 12 Crustaceans Daphnid, Daphnia magna 0.9–3.2 LC50 (LT) 1 Fish Rainbow trout: Larva 24.0 LC50 (96 h) 1 Juvenile 5.0–42.0 LC50 (96 h) 1 Subadult 34.0 LC50 (48 h) 20 Subadult 4.0 < 50.0% dead in 100 d 20 Brook trout; yearling 65.0 LC50 (96 h) 1 Air-breathing catfish, Clarias batrachus; adults: Methylmercury 430.0 LC50 (96 h) 18 Methoxyethylmercury 4300.0 LC50 (96 h) 18 Blue gourami, Trichogaster sp.; adults 70.0 LC50 (96 h) 22 (continued) © 2006 by Taylor & Francis Group, LLC 160 MERCURY HAZARDS TO LIVING ORGANISMS ciliate protozoan, Uronema nigricans, acquired tolerance to mercury after feeding on mercury- laden bacteria and subsequently exposed to increasing levels of mercury in solution (Berk et al., 1978). The phenomenon of acquired mercury tolerance in U. nigricans occurred in a single generation (Berk et al., 1978). Among coral colonies of Porites asteroides, the LC50 (72 h) value was 180.0 µg Hg/L, as HgCl 2 . Death was preceded by polyp contraction during the first 8 h, color loss within 24 h, and tissue loss within 48 h (Bastidas and Garcia, 2004). In general, salts of mercury and its organic compounds have been shown in short-term bioassays to be more toxic to marine organisms than salts of other heavy metals (Kobayashi, 1971; Conner, 1972; Schneider, 1972; Berland et al., 1976; Reish et al., 1976; Eisler and Hennekey, 1977). To oyster embryos, for example, mercury salts were more toxic than salts of silver, copper, zinc, nickel, lead, cadmium, arsenic, chromium, manganese, or aluminum (Calabrese et al., 1973); to clam embryos, mercury was the most toxic metal tested, followed, in order, by silver, zinc, nickel, and Table 8.1 (continued) Lethality of Inorganic and Organic Mercury Compounds to Selected Species of Aquatic Organisms Chemical Species, Ecosystem, Taxonomic Group, Species, and Other Variables Concentration (µµ µµ g Hg/L medium) Effect a Ref. b Amphibians Toad, Bufo bufo japonicus; tadpole 120.0 LC50 (48 h) 28 Toad, Bufo melanosticus; tadpole 56.0 LC50 (96 h) 28 Frog, Rana breviceps; tadpole 60.0 LC50 (96 h) 28 Organic Mercury: Marine Molluscs American oyster, Crassostrea virginica: Adults 50.0 for 19 days at 0–10°C to methylmercury or phenylmercury Most moribund or dead 24 Adults Survivors from above removed at day 19 and transferred to flowing mercury-free seawater All dead within 14 days 24 Crustaceans Amphipod, Gammarus duebeni 150.0 LC50 (96 h) 1 Fish Mummichog, Fundulus heteroclitus: Eggs, polluted creek (sediment content of 10.3 mg Hg/kg) 1700.0 LC50 (20 min) 21 Eggs, reference site 700.0 LC50 (20 min) 21 a Abbreviations: LT = lifetime exposure; h = hours; d = days; min = minutes. b Reference: 1, USEPA, 1980; 2, Birge et al., 1979; 3, Verma and Tonk, 1983; 4, Parker, 1979; 5, Eisler and Hennekey, 1977; 6, USEPA, 1985; 7, Thain, 1984; 8, Nelson et al., 1976; 9, Gentile et al., 1983; 10, Glickstein, 1978; 11, McClurg, 1984; 12, Best et al., 1981; 13, Jayaprakash and Madhyastha, 1987; 14, Kanamadi and Saidapur, 1991; 15, Punzo, 1993; 16, Dave and Xiu, 1991; 17, Hilmy et al., 1987; 18, Kirubagaran and Joy, 1988; 19, Diamond et al., 1989; 20, Niimi and Kissoon, 1994; 21, Khan and Weis, 1987; 22, Hamasaki et al., 1995; 23, Mayer, 1987; 24, Cunningham and Tripp, 1973; 25, Bastidas and Garcia, 2004; 26, Shah and Altindag, 2004; 27, Birge et al., 2000; 28, Paulose, 1988; 29, Ghate and Mulherkar, 1980; 30, Rao and Madyastha, 1987; 31, Punzo, 1993; 32, De Zwart and Sloof, 1987; 33, Valenti et al., 2005; 34, Unrine et al., 2004. LETHAL EFFECTS OF MERCURY 161 lead (Calabrese and Nelson, 1974). Glickstein (1978) reported an LC50 (48 h) value of 5.7 µg Hg/L, as inorganic mercury, to embryos of the Pacific oyster, Crassostrea gigas; however, embryos were relatively insensitive to mercury 24 h postfertilization, and survival was enhanced by a variety of factors, including ambient selenium concentrations. Mercury toxicity to crustaceans was markedly influenced by developmental stage, diet, sex, salinity, tissue sensitivity, and selenium. Larvae and newly molted crustaceans were more sensitive to mercury toxicity than were adults of the same species (Wilson and Conner, 1971; Vernberg et al., 1974; Shealy and Sandifer, 1975). Starved larvae of the grass shrimp had lower survival rates than fed larvae when subjected to mercury insult (Shealy and Sandifer, 1975). Also, male adult fiddler crabs (Uca pugilator) were more sensitive to mercury salts than females (Vernberg et al., 1974). Lethality of mercury salts to the porcelain crab (Petrolisthus armatus) were most pronounced at lower salinities within the range of 7 to 35‰ (Roesijadi et al., 1974). A similar pattern was recorded for the fiddler crab, Uca pugilator (Vernberg et al., 1974). Adult prawns (Leander serratus) held in lethal solutions of mercury (50.0 mg inorganic Hg/L; 1.0 mg organic mercury/L) for 3 h contained at death 320.0 to 460.0 mg Hg/kg DW in antennary gland (Corner and Rigler, 1958). High levels of selenium (> 5.0 mg/L) increased mercury toxicity to larvae of dungeness crab, Cancer magister, to levels below the LC50 (96 h) value of 6.6 µg Hg/L; however, moderate selenium values of 0.01 to 1.0 mg/L tended to decrease mercury toxicity (Glickstein, 1978). Many acute toxicity bioassays were of 96-h duration, a duration that allows the senior investi- gator and technicians alike the opportunity to enjoy an uninterrupted weekend. But it is clear from Table 8.1 that assays of 168-h duration produced LC50 values up to 45 times lower (more toxic) than did the 96-h assays, as was shown for mud snails. It is recommended that acute toxicity bioassays with mercury and other toxicants and estuarine fauna should consist of a minimal 10-day continuous exposure followed by a 10-day observation period (Eisler, 1970). 8.1.2 Vertebrates Signs of acute mercury poisoning in fish, included flaring of gill covers, increased the frequency of respiratory movements, loss of equilibrium, excessive mucous secretion, darkening of coloration, and sluggishness (Armstrong, 1979; Hilmy et al., 1987). Signs of chronic mercury poisoning included emaciation (due to appetite loss), brain lesions, cataracts, diminished response to change in light intensity, inability to capture food, abnormal motor coordination, and various erratic behaviors (Armstrong, 1979; Hawryshyn et al., 1982). Total mercury concentrations in tissues of mercury-poisoned adult freshwater fish that died soon thereafter ranged (in mg/kg fresh weight) from 6.0 to 114.0 in liver, 3.0 to 42.0 in brain, 5.0 to 52.0 in muscle, and 3.0 to 35.0 in whole body (Armstrong, 1979; Wiener and Spry, 1996). Whole body concentrations up to 100.0 mg/kg FW were reportedly not lethal to rainbow trout, Oncorhynchus mykiss, although 20.0 to 30.0 mg/kg FW in that species were associated with reduced appetite, loss of equilibrium, and hyperplasia of gill epithelium (Niimi and Lowe-Jinde, 1984). Brook trout, Salvelinus fontinalis, however, showed toxic signs and death at whole body residues of only 5.0 to 7.0 mg/kg FW (Armstrong, 1979). Some fish populations have developed a resistance to methylmercury, but only in the gametes and embryonic stage. For example, eggs of the mummichog (Fundulus heteroclitus), an estuarine cyprinodontiform fish, from a mercury-contaminated creek, when compared to a reference site, were more than twice as resistant to methylmercury (LC-50 values of 1.7 mg Hg/L vs. 0.7 mg Hg/L) when exposed for 20 min prior to combination with untreated sperm. Eggs from the polluted creek that were subjected to 1.0 or 2.5 mg CH 3 HgCl/L produced embryos with a 5.0 to 7.0% malformation frequency vs. 32.0% malformations at 1.0 mg/L and little survival at 2.5 mg/L in the reference group (Khan and Weis, 1987). Genetic polymorphism in mosquitofish (Gambusia sp.) at specific enzyme loci are thought to control survival during mercury exposure (Diamond et al., 1989). In one population of mosquitofish during acute exposure to mercury, genotypes at © 2006 by Taylor & Francis Group, LLC 162 MERCURY HAZARDS TO LIVING ORGANISMS three loci were significantly related to survival time, as was heterozygosity. However, neither genotype nor heterozygosity were related to survival in a different population of mosquitofish during acute mercury exposure (Diamond et al., 1991). Embryo-larva tests with amphibians and inorganic mercury showed that 6 of the 21 species tested were more sensitive than rainbow trout embryo-larva tests and 15 were less sensitive; however, all 21 amphibian species were more sensitive than largemouth bass embryos (Birge et al., 2000; Table 8.1). Amphibian embryos were the most sensitive stage tested to mercury and other chemicals owing to the relatively high permeability of the egg capsule at this time (Birge et al., 2000). In general, organomercurials were 3 to 4 times more lethal than inorganic mercury com- pounds to amphibians when the same species and life stage were tested (Table 8.1). Exposure pathways for adult amphibians include soils (dermal contact, liquid water uptake), water (dermal contact with surface water), air (cutaneous and lung absorption), and diet (adults are carnivores). All routes of exposure are affected by various physical, chemical, and other factors. Dietary exposure in adults, for example, is related to season of year, activity rates, food availability, consumption rate, and assimilation rates (Birge et al., 2000). Knowledge of these modifiers is necessary for adequate risk assessment of mercury as a possible factor in declining amphibian populations worldwide. 8.2 TERRESTRIAL INVERTEBRATES Methylmercury compounds at concentrations of 25.0 mg Hg/kg in soil were fatal to all tiger worms (Eisenia foetida) in 12 weeks; at 5.0 mg/kg, however, only 21.0% died in a similar period (Beyer et al., 1985). Inorganic mercury compounds were also toxic to earthworms (Octochaetus pattoni); in 60 days, 50.0% died at soil Hg 2+ levels of 0.79 mg/kg, and all died at 5.0 mg/kg (Abbasi and Soni, 1983). 8.3 REPTILES Data on mercury lethality in reptiles are scarce, and those available suggest that sensitivity may be both species and age dependent (Rainwater et al., 2005). For example, juveniles of the corn snake, Elaphe guttata, fed diets containing 12.0 mg methylmercury/kg FW diet all died within days (Bazar et al., 2002). However, adults and offspring from treated adults of the garter snake, Thamnophis sirtalis, fed diets containing up to 200.0 mg methylmercury/kg FW diet all survived and showed no sign of toxicity (Wolfe et al., 1998). 8.4 BIRDS Signs of mercury poisoning in birds include muscular incoordination, falling, slowness, fluffed feathers, calmness, withdrawal, hyporeactivity, hypoactivity, and eyelid drooping. In acute oral exposures, signs appeared as soon as 20 min post-administration in mallards, Anas platyrhynchos, and 2.5 h in ring-necked pheasants, Phasianus colchicus. Deaths occurred between 4 and 48 h in mallards and 2 and 6 days in pheasants; remission took up to 7 days (Hudson et al., 1984). In studies with coturnix, Coturnix sp., Hill (1981) found that methylmercury was always more toxic than inorganic mercury, and that young birds were usually more sensitive than older birds. Fur- thermore, some birds poisoned by inorganic mercury recovered after treatment was withdrawn, but chicks that were fed methylmercury and later developed toxic signs usually died, even if treated feed was removed. Coturnix subjected to inorganic mercury, regardless of route of administration, showed a violent neurological dysfunction that ended in death 2 to 6 h posttreatment. The withdrawal © 2006 by Taylor & Francis Group, LLC LETHAL EFFECTS OF MERCURY 163 syndrome in coturnix poisoned by Hg 2+ was usually preceded by intermittent, nearly undetectable tremors, coupled with aggressiveness toward cohorts; time from onset to remission was usually 3 to 5 days, but sometimes extended to 7 days. Coturnix poisoned by methylmercury appeared normal until 2 to 5 days posttreatment; then, ataxia and low body carriage with outstretched neck were often associated with walking. In advanced stages, coturnix lost locomotor coordination and did not recover; in mild to moderate clinical signs, recovery usually took at least 1 week (Hill, 1981). Mercury toxicity to birds varies with the form of the element, dose, route of administration, species, sex, age, and physiological condition (Fimreite, 1979). For example, in northern bobwhite chicks fed diets containing methylmercury chloride, mortality was significantly lower when the solvent was acetone than when it was another carrier such as propylene glycol or corn oil (Spann et al., 1986). In addition, organomercury compounds interact with elevated temperatures and pes- ticides, such as DDE and parathion, to produce additive or more-than-additive toxicity, and with selenium to produce less-than-additive toxicity (Fimreite, 1979). Acute oral toxicities of various mercury formulations ranged between 2.2 and about 31.0 mg Hg/kg body weight for most avian species tested (Table 8.2). Similar data for other routes of administration were 4.0 to 40.0 mg/kg for diet and 8.0 to 15.0 mg/kg body weight for intramuscular injection (Table 8.2). Residues of mercury in experimentally poisoned passerine birds usually exceeded 20.0 mg/kg FW, and were similar to concentrations reported in wild birds that died of mercury poisoning (Finley et al. 1979). In one study with the zebra finch (Poephila guttata), adults were fed methyl- mercury in the diet for 76 days at dietary levels of < 0.02 (controls), 1.0, 2.5, or 5.0 mg Hg/kg DW ration (Scheuhammer, 1988). There were no signs of mercury intoxication in any group except the high-dose group, which experienced 25.0% dead and 40.0% neurological impairment. Dead birds from the high-dose group had 73.0 mg Hg/kg FW in liver, 65.0 in kidney, and 20.0 in brain; survivors without signs had 30.0 in liver, 36.0 in kidney, and 14.0 mg Hg/kg FW in brain; impaired birds had 43.0 mg Hg/kg FW in liver, 55.0 in kidney, and 20.0 in brain (Scheuhammer, 1988). Mercury levels in tissues of poisoned wild birds were highest (45.0 to 126.0 mg/kg FW) in red-winged blackbirds (Agelaius phoeniceus), intermediate in European starlings (Sturnus vulgaris) and cowbirds (Molothrus ater), and lowest (21.0 to 54.0) in common grackles (Quiscalus quiscula). In general, mercury residues were highest in the brain, followed by the liver, kidney, muscle, and carcass. Some avian species are more sensitive than passerines (Solonen and Lodenius, 1984; Hamasaki et al., 1995). Liver residues (in mg Hg/kg FW) in birds experimentally killed by methyl- mercury ranged from 17.0 in red-tailed hawks (Buto jamaicensis) to 70.0 in jackdaws (Corvus monedula); values were intermediate in ring-necked pheasants, kestrels (Falco tinnunculus), and black-billed magpies (Pica pica) (Solonen and Lodenius; Hamasaki et al., 1995). Experimentally poisoned grey herons (Ardea cinerea) seemed to be unusually resistant to mercury; lethal doses produced residues of 415.0 to 752.0 mg Hg/kg dry weight of liver (Van der Molen et al., 1982). However, levels of this magnitude were frequently encountered in livers from grey herons collected during a massive die-off in the Netherlands during a cold spell in 1976; the interaction effects of cold stress, mercury loading, and poor physical condition of the herons are unknown (Van der Molen et al., 1982). 8.5 MAMMALS Mercury is easily transformed into stable and highly toxic methylmercury by microorganisms and other vectors (De Lacerda and Salomons, 1998; Eisler, 2000). Methylmercury affects the central nervous system in humans — especially the sensory, visual, and auditory areas concerned with coordination; the most severe effects lead to widespread brain damage, resulting in mental derange- ment, coma, and death (Clarkson and Marsh, 1982; USPHS, 1994). Methylmercury has long residence times in aquatic biota and consumption of methylmercury-contaminated fish is implicated in more than 150 deaths and more than 1000 birth defects in Minamata, Japan, between 1956 and © 2006 by Taylor & Francis Group, LLC [...]...164 MERCURY HAZARDS TO LIVING ORGANISMS Table 8. 2 Lethality to Birds of Mercury Administered by Oral, Dietary, or Other Routes Route of Administration, Organism, and Mercury Formulation Mercury Concentration and Effect Ref.a Single Oral Dose Chukar, Alectoris chukar: Ethylmercury Mallard, Anas platyrhynchos: Methylmercury Ethylmercury Phenylmercury Common bobwhite, Colinus virginianus: Methylmercury... ornata, Indian J Exp Biol., 18, 1094–1096 Glickstein, N 19 78 Acute toxicity of mercury and selenium to Crassostrea gigas embryos and Cancer magister larvae, Mar Biol., 49, 113–117 Greener, Y and J.A Kochen 1 983 Methyl mercury toxicity in the chick embryo, Teratology, 28, 23– 28 Grissom, R.E., Jr and J.P Thaxton 1 985 Onset of mercury toxicity in young chickens, Arch Environ Contam Toxicol., 14, 193–196 Guallar,... Res., 44, 272–2 78 Khera, K.S 1979 Teratogenic and genetic effects of mercury toxicity In J.O Nriagu (Ed.), The Biogeochemistry of Mercury in the Environment, p 501–5 18 Elsevier/North-Holland Biomedical Press, New York © 2006 by Taylor & Francis Group, LLC 170 MERCURY HAZARDS TO LIVING ORGANISMS Kirubagaran, R and K.P Joy 1 988 Toxic effects of three mercurial compounds on survival, and histology of the... for 28 days; LD86 500.0 mg Hg/kg diet for 28 days; LD55 500.0 mg Hg/kg diet for 28 days; LD33 2 15 15 6 6 6 LETHAL EFFECTS OF MERCURY Table 8. 2 (continued) 165 Lethality to Birds of Mercury Administered by Oral, Dietary, or Other Routes Route of Administration, Organism, and Mercury Formulation Methylmercury Methylmercury Methylmercury Zebra finch, Poephila guttata: Methylmercury Methylmercury Ring-necked... 4.0 to 40.0 mg/kg (dietary) for birds; and from 0.1 to 0.5 mg/kg body weight (daily dose) and 1.0 to 5.0 mg/kg diet for mammals © 2006 by Taylor & Francis Group, LLC 1 68 MERCURY HAZARDS TO LIVING ORGANISMS REFERENCES Abbasi, S.A and R Soni 1 983 Stress-induced enhancement of reproduction in earthworms Octochaetus pattoni exposed to chromium (VI) and mercury (II) — implications in environmental management,... Environ Res., 12, 285 –309 U.S Environmental Protection Agency (USEPA) 1 980 Ambient water quality criteria for mercury, U.S Environ Protection Agen Rep 440/ 5 -8 0-0 58 Available from Natl Tech Infor Serv., 5 285 Port Royal Road, Springfield, VA 22161 U.S Environmental Protection Agency (USEPA) 1 985 Ambient water quality criteria for mercury — 1 984 U.S Environ Protection Agen Rep 440/ 5 -8 4-0 26 136 pp Available... Aquat Toxicol., 21, 119–134 Eaton, R.D.P., D.C Secord, and P Hewitt 1 980 An experimental assessment of the toxic potential of mercury in ringed-seal liver for adult laboratory cats, Toxicol Appl Pharmacol., 55, 514–521 Eisler, R 1970 Factors affecting pesticide-induced toxicity in an estuarine fish, U.S Bur Sport Fish Wildl Tech Paper, 45, 1–20 Eisler, R 1 981 Trace Metal Concentrations in Marine Organisms. .. Methylmercury, p 3–26, October 2, 1992, Kumamoto, Japan Published by National Institute for Minamata Disease, Kumamoto 86 7, Japan Tamashiro, H., M Arakaki, H Akagi, K Hirayama, and M.H Smolensky 1 986 Methylmercury toxicity in spontaneously hypertensive rats (SHR), Bull Environ Contam Toxicol., 36, 6 68 673 Thain, J.E 1 984 Effects of mercury on the prosobranch mollusc Crepidula fornicata: acute lethal toxicity... 38, 345–351 Diamond, S.A., M.C Newman, M Mulvey, P.M Dixon, and D Martinson 1 989 Allozyme genotype and time to death of mosquitofish, Gambusia affinis (Baird and Girard), during acute exposure to inorganic mercury, Environ Toxicol Chem., 8, 613–622 Diamond, S.A., M.C Newman, M Mulvey, and S.I Guttman 1991 Allozyme genotype and time -to- death of mosquitofish, Gambusia holbrooki, during acute inorganic mercury. .. Khera, 1979; 2, Eaton et al., 1 980 ; 3, Sheffy and St Amant, 1 982 ; 4, Kucera, 1 983 ; 5, Hudson et al., 1 984 ; 6, Ronald et al., 1977; 7, USPHS, 1994; 8, Ropek and Neely, 1993; 9, Wren et al., 1 987 a; 10, Tamashiro et al., 1 986 ; 11, Kitamura, 1971; 12, Takizawa, 1993; 13, O’Connor and Nielsen, 1 980 8. 6 SUMMARY For all organisms tested, early developmental stages were the most sensitive, and organomercury compounds . Francis Group, LLC 1 58 MERCURY HAZARDS TO LIVING ORGANISMS Table 8. 1 (continued) Lethality of Inorganic and Organic Mercury Compounds to Selected Species of Aquatic Organisms Chemical Species,. acquired tolerance to mercury after feeding on mercury- laden bacteria and subsequently exposed to increasing levels of mercury in solution (Berk et al., 19 78) . The phenomenon of acquired mercury tolerance. LLC 164 MERCURY HAZARDS TO LIVING ORGANISMS Table 8. 2 Lethality to Birds of Mercury Administered by Oral, Dietary, or Other Routes Route of Administration, Organism, and Mercury Formulation Mercury