Can selective breeding reduce the heavy metals content of Pacific oysters (Crassostrea gigas), and are there trade-offs with growth or survival?ABSTRACT Oyster producers in the Pacific Northwest region
The Northwest Region of the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. export large quantities of oysters to international markets. Proposed changes to international limits for heavy metals heavy metals,
n.pl metallic compounds, such as aluminum, arsenic, cadmium, lead, mercury, and nickel. Exposure to these metals has been linked to immune, kidney, and neurotic disorders. content in shellfish shellfish, popular name for certain edible mollusks (see Mollusca), e.g., oysters, clams, and scallops, and for certain edible crustaceans, e.g., crabs, lobsters, and shrimps. All are aquatic invertebrates with shells; they are not fish. could drastically curtail exports and impact the viability of this environmentally-friendly industry. "Supply-side" solutions such as moving oyster farms to uncontaminated sites or short-term depuration depuration (dēˈ·py would incur substantial costs in terms of labor and infrastructure and displace dis·place
tr.v. dis·placed, dis·plac·ing, dis·plac·es
1. To move or shift from the usual place or position, especially to force to leave a homeland: workers in already economically challenged coastal communities, whereas selective breeding
Selective breeding in domesticated animals is the process of developing a cultivated breed over time. could benefit both producers and consumers within the current infrastructure. We studied the feasibility of selective breeding to reduce heavy metal content through a quantitative genetic analysis of heavy metals accumulation in the Pacific oyster Pacific oyster
An oyster (Crassostrea gigas) cultured in the United States and Europe, having a scalloped shell and a fruity flavor. Also called Portuguese oyster. , Crassostrea gigas by opportunistically sampling a factorial factorial
For any whole number, the product of all the counting numbers up to and including itself. It is indicated with an exclamation point: 4! (read “four factorial”) is 1 × 2 × 3 × 4 = 24. mating experiment initiated in 2000 to study the effects of parent size on offspring growth and survival. The experiment consisted of all possible crosses among six males (sires) and five females (dams). At harvest, we measured four performance traits (yield, survival, whole oyster live weight and shucked meat dry weight) and the accumulated levels of four heavy metals (copper, lead, zinc and cadmium cadmium (kăd`mēəm) [from cadmia, Lat. for calamine, with which cadmium is found associated], metallic chemical element; symbol Cd; at. no. 48; at. wt. 112.41; m.p. 321°C;; b.p. 765°C;; sp. gr. 8. ). Analyses of variance testing for sire and dam effects and bootstrap See boot.
(operating system, compiler) bootstrap - To load and initialise the operating system on a computer. Normally abbreviated to "boot". From the curious expression "to pull oneself up by one's bootstraps", one of the legendary feats of Baron von Munchhausen. estimates of heritability heritability /her·i·ta·bil·i·ty/ (her?i-tah-bil´i-te) the quality of being heritable; a measure of the extent to which a phenotype is influenced by the genotype.
1. showed that all of these traits have a genetic basis. Further, half-and full-sib family means correlations revealed genetic trade-offs between copper and cadmium content and performance traits. Preliminary indications are that selective breeding to reduce heavy metals accumulation is possible, but that genetic trade-offs between metal content and performance should be taken into account in designing any program of selective breeding in this species.
KEY WORDS: Crassostrea gigas, cadmium, copper, lead, zinc, heavy metals contamination, depuration, quantitative genetics quantitative genetics
The scientific study of the statistical analysis of the effects that heredity and environment have on phenotypic variation. , genetic correlation
Oyster aquaculture aquaculture, the raising and harvesting of fresh- and saltwater plants and animals. The most economically important form of aquaculture is fish farming, an industry that accounts for an ever increasing share of world fisheries production. is an important economical activity in the Pacific Northwest region of the United States where traditional finfish finfish
fish with fins, that is teleosts, elasmobranches, holocephalids, agnathids and cephalochordates; also a fish marketer's term used to include that section of marketable fish which is neither shellfish nor molluscs. and shellfish capture fisheries fisheries. From earliest times and in practically all countries, fisheries have been of industrial and commercial importance. In the large N Atlantic fishing grounds off Newfoundland and Labrador, for example, European and North American fishing fleets have long are generally overexploited and increasingly regulated. Since the early part of the 20th century, after the collapse of the fishery for the native Olympia oyster Olympia oyster
A small oyster (Ostrea lurida) native to the Pacific coast of North America.
[After Olympia2.] , Ostrea concaphila, oyster production in this region has been dominated by the normative Pacific oyster, Crassostrea gigas. Prior to the 1970s, the west coast oyster industry was heavily dependent on shipments of oyster seed on cultch cultch
Variant of culch. from Japan, but with the development of hatchery hatchery
a commercial establishment dedicated to the hatching of bird eggs to provide day old chicks and poults to the poultry industry.
the contents of unfertilized eggs. Used in petfood manufacture. technology on the west coast (see Clark & Langmo 1979 for a review) and increased regulation over the movement of live shellfish, the industry has evolved to rely almost entirely on hatchery production. Oysters grown in the Pacific Northwest region are marketed internationally, and foreign markets are particularly profitable for growers (W. Dewey, X. Liu, P. Taylor pers. comm to MDC (1) (Mobile Daughter Card) See riser card.
(2) See Meta Data Coalition. ).
Bivalve bivalve, aquatic mollusk of the class Pelecypoda ("hatchet-foot") or Bivalvia, with a laterally compressed body and a shell consisting of two valves, or movable pieces, hinged by an elastic ligament. mollusks in general, and Pacific oysters in particular, are efficient bioaccumulators of heavy metals such as lead, copper, zinc and cadmium (Shulkin et al. 2003), potentially at concentrations toxic to humans who consume them in large quantities. Concerns over heavy metals, especially cadmium, in shellfish have recently lead to the closure of oyster farms in heavily contaminated contaminated,
v 1. made radioactive by the addition of small quantities of radioactive material.
2. made contaminated by adding infective or radiographic materials.
3. an infective surface or object. areas of France (Geffard et al. 2002). The Codex codex
Manuscript book, especially of Scripture, early literature, or ancient mythological or historical annals. The earliest type of manuscript in the form of a modern book (i.e. Alimentarus Commission, created in 1963 by the Food and Agriculture Organization and the World Health Organization (http://www.codexalimentarius.net/) is currently considering new international standards for cadmium content in shellfish and other agricultural products of 1 [micro]/g wet tissue weight (ftp://ftp.fao.org/codex/ccfac33/fa01_28e.pdf). Typically, once an international limit is set by Codex, member countries, including the United States, adopt the same standards for not only international, but also domestic interstate sales, and any product exceeding the standards is considered adulterated a·dul·ter·ate
tr.v. a·dul·ter·at·ed, a·dul·ter·at·ing, a·dul·ter·ates
To make impure by adding extraneous, improper, or inferior ingredients.
1. Spurious; adulterated.
2. Adulterous. . Because oysters grown in the Pacific Northwest region of the United States sometimes contain levels of cadmium above the proposed limits (Christy chris·ty
Variant of christie. et al. 2004 see also http://www.pacshell.org/Cadmium.htm), these new regulations could threaten export markets for United States producers. Also, the USFDA USFDA United States Food & Drug Administration established 3.7 [micro]/g of cadmium in shellfish as a "level of concern" in 1993, and domestic consumers are increasingly uneasy about the risks associated with heavy metal contamination.
Several strategies to limit the heavy metal content of oysters reaching these markets are possible. Perhaps the simplest approach from the biologic perspective would be to control the availability of metals in the growing environment. Oysters clearly acquire the heavy metals that they accumulate from the environment, and "supply-side" solutions aimed at controlling the environmental availability of heavy metals could be effective if they can be implemented. Reinfelder et al. (1997), for example, found that American oysters (Crassostrea virginica) assimilated approximately 70% of the cadmium, selenium selenium (səlē`nēəm), nonmetallic chemical element; symbol Se; at. no. 34; at. wt. 78.96; m.p. 217°C;; b.p. about 685°C;; sp. gr. 4.81 at 20°C;; valence −2, +4, or +6. and zinc contained in their food. Ke and Wang (2001) studied the bioaccumulation bi·o·ac·cu·mu·la·tion
The increase in the concentration of a substance, especially a contaminant, in an organism or in the food chain over time. of the same three metals in Crassostra rivularis and Saccostrea glomerata, and found that most of the retained metals came from ingested in·gest
tr.v. in·gest·ed, in·gest·ing, in·gests
1. To take into the body by the mouth for digestion or absorption. See Synonyms at eat.
2. particles rather than from dissolved sources and that the assimilation efficiencies for all three metals ranged from about 25% to 80%. These data clearly argue that this approach warrants serious investigation because of the strong influence of heavy metal availability (especially in food organisms) on accumulation. Other researchers are collecting baseline environmental data to describe spatial variation in the environmental availability of cadmium and the levels accumulated by oysters in the Pacific northwest (Christy et al. 2004 see also http://www.pacshell.org/ Cadmium.htm). This parallel effort should reveal the magnitude of variation in heavy metal availability and its spatial patterning. However, managing the availability of cadmium and other metals in the environment is likely to require either large-scale changes in watershed management and land use that contribute to heavy metal availability or the concentration of oyster farms in areas with low availability accompanied by restrictions on the future activities allowed in these areas. Because these are matters policy rather than biology, we will not address them further here, except to point out that implementing this approach would clearly require substantial changes to either where oysters are farmed or what other activities are allowable in nearby areas.
Depurating or otherwise decontaminating metal-containing shellfish before they reach markets could also provide safer oysters to markets. The use of depuration strategies, however, is difficult to assess with the available information. Greig and Wenzloff (1978) and Zaroogian (1979) found that in C. virginica, depuration of experimentally contaminated oysters for 48 and 56 wk respectively had no effect on cadmium concentrations (though Zaroogian did observe decreases in the total quantity of cadmium accompanied by a decrease in tissue weight). Geffard et al. (2002) studied the kinetics kinetics: see dynamics.
Kinetics (classical mechanics)
That part of classical mechanics which deals with the relation between the motions of material bodies and the forces acting upon them. of heavy metal elimination from Pacific oysters (C. gigas) grown in a contaminated estuary estuary (ĕs`chĕr'ē), partially enclosed coastal body of water, having an open connection with the ocean, where freshwater from inland is mixed with saltwater from the sea. in France and found that this species retains accumulated heavy metals for long periods after being transferred to cleaner areas. In Geffard's study, cadmium was eliminated more quickly than copper or zinc, but still, 4 mo of deputation was necessary to reduce cadmium to safe levels. In contrast, van Dolah et al. (1987), and Okazaki and Panietz (1981) found that cadmium, copper and zinc could be reduced quickly through depuration. Wallner-Kersanach et al. (2000) showed that the efficacy of depuration depends on the details of their exposure, which could explain the discrepancies between these studies. Oysters exposed briefly (60 days) to high levels of copper were able to eliminate 30% of their copper content in 30 days, whereas resident oysters from the same area eliminated only 9% of their copper content in the same period. In addition, van Dolah et al. (1987), and Amiard-Triquet et al. (1991) noted that the kinetics of metal elimination are influenced by environmental factors such as salinity, temperature and humic acid Noun 1. humic acid - a dark brown humic substance that is soluble in water only at pH values greater than 2; "the half-life of humic acid is measured in centuries"
humic substance - an organic residue of decaying organic matter concentration. Geffard et al. (2002) argue that these variable results can be explained by the facts that (a) environmental factors alter the distribution of accumulated metals among various tissues and the degree to which they are bound to cytosolic ligands versus in solution and (b) the soluble fraction is more easily eliminated through depuration. If this view is correct, then growing oyster at sites contaminated with heavy metals for long periods could make subsequent depuration impractical. However, even if depuration is possible, implementing this approach would minimally require identifying appropriate sites and regularly moving vast quantities of materials to these sites, at considerable expense.
In this study, we address the feasibility of selective breeding to reduce the heavy metal content of cultured Pacific oysters with the idea that if oyster strains that naturally accumulate less heavy metals were available, growers would need only to change their source of broodstock whereas other approaches require substantial changes to policy and/or infrastructure. Due the urgency of this issue for the cultured oyster industry and the time that is required to initiate a new experiment, we opportunistically sampled an existing quantitative genetic field experiment to assay the heavy metal content of oysters with known genetic relationships. Because this experiment was initially designed to examine the relationship between parental size and the growth and survival of their progeny PROGENY - 1961. Report generator for UNIVAX SS90. (Evans 2004), the male parental animals consisted of large and small animals, sampled nonrandomly, and this could potentially bias the results. Nonetheless, this initial examination of the degree to which heavy metals accumulation is under genetic control provides important and timely insights regarding the prospects for manipulating heavy metal accumulation through selective breeding and has important implications for ongoing selective breeding efforts and commercial producers.
MATERIALS AND METHODS
The parents came from a previous experiment (Brooks 2000) in which individually tagged adult oysters from unselected pedigreed oyster families were deployed in lantern lantern
held by Judas, leading officers to Christ. [N.T.: John 18:3]
See : Passion of Christ nets at two locations within Yaquina Bay Yaquina Bay (pronounced ya kwin na or, rarely, ya keen ah) is a small bay partially within Newport, Oregon, United States, located where the Yaquina River flows into the Pacific Ocean. Its area is about 8 km² (3.2 mi²). , Oregon (44.6[degrees]N, 124.1[degrees]W) during Summer 1998. The first site was located approximately 3 km from the mouth of Yaquina Bay ("downriver down·riv·er
adv. & adj.
Toward or near the mouth of a river; in the direction of the current: swam downriver; a downriver canoe race.
Adv. 1. "), the second site was located approximately 15 km up the Yaquina River The Yaquina River (yuh-KWEN-uh) is a river, approximately 50 mi (80 km) long, on the Pacific coast of Oregon in the United States. It drains an area of the Central Oregon Coast Range west of the Willamette Valley near Newport. at a commercial shellfish lease-site ("upriver"). As a continuation of research initiated by Brooks (2000), body weights of all tagged oysters were periodically measured from plant-out in Spring 1998 until harvest in Summer 2001. For this experiment, which was originally designed to test the hypothesis that the size of parents affects the performance of their progeny (Evans 2004), a set of 30 families was created by crossing the three largest males and the three smallest males from the downriver population with five females randomly selected females from the downriver population (i.e., 6 male x 5 female factorial cross). Crosses among full-siblings were avoided. Table 1 shows the details of this mating design.
Hatchery and Nursery Protocol
During Summer, 2001, these parents were held in 18[degrees]C sand-filtered seawater seawater
Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine. and fed a mixture of Isocrysis galbana (Iso) and Cheatoceros calcitrans (Cc) at a concentration of approximately 50,000-80,000 cells [mL.sup.-1] until ready to spawn To launch another program from the current program. The child program is spawned from the parent program.
(operating system) spawn - To create a child process in a multitasking operating system. E.g. . Animals were stripped-spawned as per Langdon et al. (2003) in Fall 2001. Fertilized fer·til·ize
v. fer·til·ized, fer·til·iz·ing, fer·til·iz·es
1. To cause the fertilization of (an ovum, for example).
2. eggs were allowed to develop into veliger ve·li·ger
A larval stage of a mollusk characterized by the presence of a velum.
[New Latin v larvae Larvae, in Roman religion
Larvae: see lemures. (D-larvae) for 24 h in cross-specific 20-L containers filled with 25[degrees]C, 0.2-[micro]m filtered seawater. D-larvae from each cross were then stocked into family-specific 100-L larval larval
1. pertaining to larvae.
see cutaneous and visceral larva migrans. culture containers at a concentration of 10 larvae [mL.sup.-1]. Larvae were fed daily with a mixture of Iso and Cc at concentrations ranging from 30,000-80,000 cells [mL.sup.-1], depending on age (Breese & Malouf 1975). Larval tanks were drained through sieves and refilled with 25[degrees]C 0.2 [micro]m filtered seawater twice per week. For the first week, larvae were retained on 37 [micro]m sieves. During the second week, larvae were retained on 80 [micro]m sieves and densities reduced to 1 larva larva, in zoology
larva, independent, immature animal that undergoes a profound change, or metamorphosis, to assume the typical adult form. Larvae occur in almost all of the animal phyla; because most are tiny or microscopic, they are rarely seen. [mL.sup.-1]. During the third week, larval cultures were drained through 243 [micro]m and 80 [micro]m sieves. All larvae retained on 243 [micro]m sieves were exposed to 2 x [10.sup.-4] M epinephrine to induce metamorphosis metamorphosis (mĕt'əmôr`fəsĭs) [Gr.,=transformation], in zoology, term used to describe a form of development from egg to adult in which there is a series of distinct stages. (Coon coon: see raccoon. et al. 1986).
Successfully metamorphosed spat were transferred to family-specific 15-cm diameter upwellers. Upwellers were held in a semi recirculating system that received approximately 6 exchanges [d.sup.-1] of 25[degrees]C UV-irradiated 1 [micro]m filtered seawater. Once all larvae had metamorphosed (approximately 4 wk post harvest), the number of spat per upweller was randomly thinned to 10,000. Spat were allowed to grow until retained on a 1.4 mm sieve, then transferred to family-specific 28-cm diameter upwellers in a larger upwelling up·well·ing
1. The act or an instance of rising up from or as if from a lower source: an upwelling of emotion.
2. system. These larger upwellers were supplied with 18[degrees]C 1-[micro]m filtered seawater delivered at approximately 2.8 1 [min.sup.-1] and fed an Iso/Cc mixture at a final concentration of approximately 50,000-80,000 cells [mL.sup.-1]. Once all animals were transferred from the 15-cm upwellers, the number of oysters per 28-cm upweller was randomly thinned to 5000. Oysters were allowed to grow until retained on a 6.4 mm sieve, before being transferred to family-specific spat bags (2-mm mesh) held in storage tanks. Storage
tanks received ambient 1-[micro]m filtered seawater (mean 9.5[degrees]C; range 7.0[degrees]C to 13.68[degrees]C) and batch-fed to a final concentration of approximately 100,000 cell [mL-.sup.1] of a Cc/Iso mixture for 8 h, twice per week. The reduced temperature In thermodynamics, the reduced temperature of a fluid means the actual temperature, divided by its critical temperature.
It is often used in thermodynamical formulas, e.g. and limited feeding limited feeding
see restricted feeding. was intended to slow oyster growth, minimizing variation in spat weight within and between cultures prior to planting in the field (Langdon et al. 2003). After approximately 80% of the oysters were sieved from the 28-cm upwellers, spat in the storage tank were counted and weighed for subsequent planting in the field. Because of variable performance in the nursery, some crosses did not produce enough spat to plant-out and evaluate in the field and only 26 of 30 crosses were deployed in the field (Table 1).
In Spring 2002, 50 randomly selected seed oysters from each family were weighed and stocked into two replicate compartments in each of five vertical blocks in 10-tier lantern nets (0.3-m diameter, 2 mm mesh) for a total of 10 replicates per family. Blocking was conducted to account for potential variation in performance traits caused by water depth. Variable survival in the nursery resulted in some families having fewer than desired individuals, and therefore < 10 replicates. Stocked lantern nets were suspended from a raft at the upriver field site. In July of 2004 (after 866 days in the field) all live oysters from each replicate were cleaned of biotic biotic /bi·ot·ic/ (bi-ot´ik)
1. pertaining to life or living matter.
2. pertaining to the biota.
1. Relating to life or living organisms. and abiotic a·bi·ot·ic
Nonliving: The abiotic factors of the environment include light, temperature, and atmospheric gases.
a fouling, counted, and their collective weight measured to the nearest gram. These data allowed for replicated estimates of yield and survival in the field. Survival was measured as the proportion of the 50 seed oysters planted that were alive at harvest. Yield was measured as the total weight of the surviving oysters in each lantern net compartment because all lantern net compartments were initially stocked with Adj. 1. stocked with - furnished with more than enough; "rivers well stocked with fish"; "a well-stocked store"
furnished, equipped - provided with whatever is necessary for a purpose (as furniture or equipment or authority); "a furnished apartment"; exactly 50 seed oysters. After these compartment-level data were collected, all of the surviving oysters were pooled within blocks, returned to the Hatfield Marine Science Center, and held in flow-through tanks, whereas subsequent measurements were taken (2-3 days). For the purposes of this study, we randomly sampled 10 animals from each family from two of the five blocks (the deepest and shallowest), and individually weighed them to the nearest gram. We then carefully opened their shells using knives dipped in weak acid and thoroughly rinsed with running distilled water Noun 1. distilled water - water that has been purified by distillation
H2O, water - binary compound that occurs at room temperature as a clear colorless odorless tasteless liquid; freezes into ice below 0 degrees centigrade and boils above 100 degrees centigrade; to prevent cross-contamination, removed the meats, blotted them dry using paper towels, and weighed individual meats to the nearest 0.1 g. We then froze the meats at -80[degrees]C in individually marked plastic bags.
Heavy Metals Assays
In late July and August 2004, we freeze-dried the oyster meats by removing them from the freezer, quickly opening their individual bags, and placing them into the vacuum chamber of a Labconco freeze dryer still in their individual bags. When they were completely dried, we crushed each meat to a fine powder inside its individual bag using a Seward Stomacher 80 blender. We later used small subsamples of the powdered tissues for heavy metals analysis using inductively in·duc·tive
1. Of, relating to, or using logical induction: inductive reasoning.
2. Electricity Of or arising from inductance: inductive reactance. coupled plasma--optical emission spectrophotometry spectrophotometry
Branch of spectroscopy dealing with measurement of radiant energy transmitted or reflected by a body as a function of wavelength. The measurement is usually compared to that transmitted or reflected by a system that serves as a standard. (ICP-OES ICP-OES Inductively Coupled Plasma-Optical Emission Spectroscopy ). The microwave digestion of oyster tissue in preparation for ICP-OES analysis began by combining 500 mg freeze-dried oyster tissue and 15 mL 6 M nitric acid nitric acid, chemical compound, HNO3, colorless, highly corrosive, poisonous liquid that gives off choking red or yellow fumes in moist air. It is miscible with water in all proportions. in a 100 mL Teflon vessel. The vessel was then loaded into an Ethos Labstation microwave (Milestone, Inc., Shelton, Connecticut Shelton is a city in Fairfield County, Connecticut, United States. History
The town was split off from Stratford in 1789, as Huntington (named for Samuel Huntington). ) and digested using Milestone application method #04-012. After digestion, the vessel was removed from the microwave and brought up to a final volume of 45 mL with Milli-Pore deionized water Deionized water (DI water or de-ionized water; also spelled deionised water, see spelling differences) is water that lacks ions, such as cations from sodium, calcium, iron, copper and anions such as chloride and bromide. . Quantification of copper (Cu), Zinc (Zn), Lead (Pb) and Cadmium (Cd) in the digested oyster tissue was preformed using a Perkin Elmer 4300 ICP-OES. The detection limits for Cd, Cu, Pb and Zn in oyster tissue were 0.05, 1.5, 0.001 and 1.0 mg [kg.sup.-1] d. wt., respectively. The instrument detection limit for Cd, Cu, Pb and Zn were 0.02, 0.02, 0.001 and 0.001 mg [L.sup.-1], respectively. The tissue sample recovery rate for Cd, Cu, Pb and Zn were all within 100% [+ or -] 10%. The raw data were then expressed as [micro]g of metal [g.sup.-1] dry tissue weight.
We first tested for significant effects of blocks (= depths), sires, dams and sire-by dam interaction on each of the eight characters measured using 2-way analysis of variance (ANOVA anova
see analysis of variance.
ANOVA Analysis of variance, see there ) performed using the PROC (language) PROC - The job control language used in the Pick operating system.
["Exploring the Pick Operating System", J.E. Sisk et al, Hayden 1986]. GLM GLM Global Language Monitor
GLM Global Marine (stock symbol)
GLM Graduated Length Method (ski instruction)
GLM Good Looking Mom (used in pediatric practices)
GLM God Loves Me procedure in the SAS (1) (SAS Institute Inc., Cary, NC, www.sas.com) A software company that specializes in data warehousing and decision support software based on the SAS System. Founded in 1976, SAS is one of the world's largest privately held software companies. See SAS System. statistical package version 8 (http://v8doc.sas.com/sashtml/). In these analyses, we treated sire and dam effects as fixed factors because the sires were a nonrandom sample from the entire population. Extrapolating from these analyses to the entire population is, therefore tenuous because the parents we used could be a nonrepresentative sample of the larger population from which they came.
We next estimated the broad-sense heritabilities of each of the traits we measured by treating the data as a set of 26 full-sib families, essentially ignoring the factorial structure of the matings. The sharing of parents among full-sib families is most likely to reduce the variation among families and therefore provide conservative estimates of broad-sense heritabilities. We calculated these estimates and their standard errors using the h2boot program written by Patrick Phillips [http://www.uoregon.edu/~pphil/software.html; (Phillips & Arnold 1999)]. This program uses a distribution-free bootstrapping Bootstrapping
A procedure used to calculate the zero coupon yield curve from market figures.
Since the T-bills offered by the government are not available for every time period, the bootstrapping method is used to fill in the missing figures in order to derive the approach to obtain point estimates and standard errors of the heritability of each trait as well as a nonparametric P value. These P values are the proportion of bootstrap samples, which distributions overlap zero. For these analyses, we first removed variance attributable to blocks by performing 1-way ANOVA on the raw data and performing the bootstrap analyses on the block-corrected residuals. All of these analyses used 5,000 bootstrap resamplings of the data.
Finally, we estimated the genetic correlations among the variables as standard product-moment correlations among the family means for all pairs of traits (Falconer Falconer
prison where former professor Farragut, who had killed his brother, witnesses the torments and chaos of the penal system. [Am. Lit.: Cheever Falconer in Weiss, 151]
See : Imprisonment & Mackay 1996) For these estimates, we again used the block-adjusted data, and reduced these data to the means of 2 different types of families: (1) the six paternal PATERNAL. That which belongs to the father or comes from him: as, paternal power, paternal relation, paternal estate, paternal line. Vide Line. half-sib families, which provides an estimate of the purely additive or strict sense genetic correlation and (2) the 26 full-sib family means, which, because of the inclusion of the nonadditive influences of dominance and epistasis e·pis·ta·sis
n. pl. e·pis·ta·ses
1. A film that forms over the surface of a urine specimen.
2. An interaction between nonallelic genes, especially an interaction in which one gene suppresses the expression of , estimates the broad-sense genetic correlation.
The eight characters we studied are described in Table 2, and summary statistics are presented in Table 3. Several overall points are worth mentioning here. First, overall, survival was low by industry standards, averaging 27% and indicating that the conditions in the Yaquina Bay during the period of this experiment were relatively stressful for Pacific oysters. Second, most of the traits we measured have quite high levels of overall phenotypic phe·no·type
a. The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences.
b. variation, with coefficients of variation ranging from about 0.3-0.75. It should be noted that the levels of heavy metals that we report here are on a dry weight basis whereas the regulatory limits discussed in the Introduction are expressed in terms of wet weight. Overall, dry meat weight averaged 19.8% of wet meat weight. Finally, because this experiment was originally designed for a different purpose, we did not collect any data on cadmium availability in either the hatchery or the field. However, all the animals were reared in the same conditions at the same time, so any variation in metals content is attributable to differential uptake rather than availability.
Table 4 shows the results of the 2-way analyses of variance for each character. Blocks had significant effects only on dry meat weight and cadmium content. There were significant main effects of sires for all response variables except zinc content and significant dam effects on all the traits we measured. In addition, there were significant sire-by-dam interactions for live weight, dry meat weight and all four metals. It should be noted, however, that all of the characters for which we found significant sire-by-dam interactions were measured on individuals and that the error degrees of freedom for the bag-level measurements and the individual-level measurements are very different (66 vs. 468). As a result, the power of the tests for interaction effects is much greater for the measurements taken on individuals.
Bootstrap estimates of broad-sense heritability range from 0.325-1.29 and all the traits we measured have heritabilities that differ significantly from zero (Table 5). In theory, heritabilities, being the proportion of total variance attributable to genetic causes, are constrained con·strain
tr.v. con·strained, con·strain·ing, con·strains
1. To compel by physical, moral, or circumstantial force; oblige: felt constrained to object. See Synonyms at force.
2. to fall between zero and one, but statistical estimates can fall outside of this interval caused by sampling errors and the fact that heritability is calculated by multiplying the observed among-family variance component by the reciprocal of the coefficient of relatedness to estimate the numerator numerator
the upper part of a fraction.
see additive genetic relationship.
numerator Epidemiology The upper part of a fraction of the proportion (Falconer & Mackay 1996), magnifying estimation errors. All of the heritability estimates greater than the theoretical maximum are for traits measured not on individuals but on growing compartments (i.e., yield and survival). The inability to measure these traits on individuals effectively reduces the data to compartment means, resulting in smaller sample sizes for these traits. Furthermore, the inability to estimate the variance among individuals within compartments for these traits has two other effects. First, it is unclear what the coefficient of relatedness is for compartments that share both parents. Whereas it is clear that the individuals within compartments are full-sibs with a coefficient of relatedness of 0.5, taken as a group, replicate compartments are essentially resamplings of the same full-sib families and thus might best be viewed as genetic clones with a coefficient of relatedness of one. In this case, the heritability estimates for yield and survival presented in Table 5 should be divided by two. Second, reducing the data to compartment means reduces the total phenotypic variance estimate because the sampling variance among individuals cannot be estimated and is necessarily excluded. This is expected to upwardly bias the heritability estimates of traits that cannot be measured on individuals because the total phenotypic variance appears as the denominator in heritability estimates.
Turning to the genetic correlations among traits and first examining correlations estimated using paternal half-sib family means, if (taking into account that these correlations use only six data points) we accept a liberal P value of <0.1 as suggestive of suggestive of Decision making adjective Referring to a pattern by LM or imaging, that the interpreter associates with a particular–usually malignant lesion. See Aunt Millie approach, Defensive medicine. a significant relationship, Table 5 shows positive relationships between yield and survival and between dry meat weight and both survival and live weight. For heavy metal accumulation, there is evidence that copper content is positively correlated with yield, survival and zinc content but no evidence that lead content is correlated with any other traits. Cadmium in contrast may be positively correlated with yield and survival but negatively correlated with meat dry weight.
The correlations among the 26 full-sib family means provide more powerful tests of significance. Using the standard criterion of P < 0.05 for statistical significance and looking first at the correlations among performance traits, our data indicate that yield is positively correlated with survival; survival is positively correlated with dry meat weight; and dry meat weight and live weight are positively correlated. The correlations between the levels of bioaccumulated heavy metals and performance traits vary among the four metals assayed. Copper content is positively correlated with yield and survival but negatively correlated with the dry weight of the shucked meat. Lead content, in contrast, is uncorrelated with any of the performance traits we measured. Zinc is uncorrelated with yield, survival or live weight but negatively correlated with dry meat weight. Cadmium content is positively correlated with yield and survival, uncorrelated with live weight and negatively correlated with dry meat weight. Copper, zinc and cadmium levels are mutually positively correlated but uncorrelated with lead levels.
Comparing the half- and full-sib family means correlations reveals a high level of agreement between these two estimates of the genetic correlation. Full-sib family means correlations produce, as expected, more significant results, but in all cases where the full-sib family means correlation is significant the signs of the full and half-sib correlations agree. In addition, there are no significant half-sib family correlations that are not also significant when estimated as full-sib correlations.
Because of the limited number of parents used in this study, the results must be interpreted with caution. Even so, our data support the hypotheses that all of the traits we measured are under considerable genetic control and that populations of C. gigas are likely to harbor substantial genetic variation for all of these traits. The significant sire-by-dam interactions for live weight, dry meat weight and the four metals we measured further indicate that non-additive genetic effects also affect these characters and that the broad-sense heritabilities we estimated using full-sib families probably overestimate o·ver·es·ti·mate
tr.v. o·ver·es·ti·mat·ed, o·ver·es·ti·mat·ing, o·ver·es·ti·mates
1. To estimate too highly.
2. To esteem too greatly. the narrow-sense heritabilities.
That we found high heritabilities for performance traits agrees well with previous work in a variety of oyster species. Lannan (1971, 1972) first reported the heritability of growth traits in Pacific oysters, and found that the early larval growth and survival measured at 12 mo postspawning had heterabilities >0.2, but reduced heritabilities at 18 mo. Newkirk et al. (1977) reported that the heritability for larval growth rate in eastern oysters The eastern oyster, Crassostrea virginica, also known as the American oyster, Atlantic oyster, or the Virginia oyster, is a species of oyster that is native to the eastern seaboard of North America. was in the range of 0.25-0.5. In Pacific oysters, Hedgecock et al. (1993) reported a heritability of 0.2 for size at the time of harvest. Degremont et al. (2002) reported high heritability (>1) for survival of adult Pacific oysters in France, and Ernande et a1.(2003) found that whereas most larval survival and size traits were heritable her·i·ta·ble
1. Capable of being passed from one generation to the next; hereditary.
2. Capable of inheriting or taking by inheritance. , growth rate was not, nor were juvenile characters. Researchers in Maine have reported a 25% reduction in the time required for C. virginica to reach market size through artificial selection (Barber et al. 1998, Davis & Barber 1999), and an ongoing selection program in Pacific oysters has resulted in substantial single-generation genetic gain of approximately 9.5% for yield compared with unselected controls and a realized heritability estimated variously from 0.01-0.32 depending on the cohort analyzed (Langdon et al. 2003).
This study is, however, to the best of our knowledge, the first to report heritability estimates for the bioaccumulation of heavy metals in shellfish and the first evidence that there are substantial genetic correlations between heavy metal accumulation and performance characters.
The positive full-sib genetic correlations we observed between copper and cadmium content and survival and yield, imply that natural selection or selective breeding for either survival or yield will likely produce a correlated response correlated response
change in an unselected character resulting from genetic selection of another character. that raises the tissue concentrations of both of these heavy metals. Single-trait selection to reduce the copper and/or cadmium content of oyster meats is likely to simultaneously reduce survival and yield. This makes intuitive sense if bioaccumulation of heavy metals by incorporation into insoluble insoluble /in·sol·u·ble/ (in-sol´u-b'l) not susceptible of being dissolved.
Not soluble. complexes is an important mechanism by which bivalves mitigate the toxic effects of heavy metals exposure and genotypes more able to set heavy metals safely aside in less reactive forms better avoid the toxic effects of exposure.
On the other hand, copper, cadmium and zinc all show negative genetic correlations with individual dry meat weight. Thus selection for larger meats could lower the concentrations of these three metals and selection for lower concentrations of copper, cadmium or zinc could result in not only fewer surviving oysters and lower yield as mentioned earlier but also larger meats. These results seem at first to he counterintuitive coun·ter·in·tu·i·tive
Contrary to what intuition or common sense would indicate: "Scientists made clear what may at first seem counterintuitive, that the capacity to be pleasant toward a fellow creature is ... in that we might expect that animals that devote more metabolic energy to detoxifying heavy metals would do so at the expense of individual growth. One possibility is that fast-growing oysters somehow process particulate matter particulate matter
n. Abbr. PM
Material suspended in the air in the form of minute solid particles or liquid droplets, especially when considered as an atmospheric pollutant.
Noun 1. in the water differently than slow-growing animals such that high-metal particles are eliminated as pseudofeces rather than ingested. It would be interesting, therefore, to compare the distribution of heavy metals among different sized particles in nature and to test whether genotypes of oysters that differ in metal content also differ in their utilization of different-sized particles.
Another, perhaps more far-fetched, possibility is that the differences in metals concentration are related to variance in reproductive effort. C. gigas develop gonads and gametes, but only rarely spawn in the cold-water temperatures of most Pacific Northwest estuaries, including Yaquina Bay. However, the summer of 2004 was unusually hot and dry in the Yaquina Bay area. If some of the families we used in this experiment were more prone to spawning, and if heavy metals are less concentrated in gonadal gonadal
pertaining to or arising from a gonad. See also testicular, ovarian.
cords formed by epithelial cells which migrate from the mesonephric tubules in the embryo to the gonadal ridge and establish the indifferent tissue or gametes, then oysters that had spawned would have smaller total meat weights but similar overall metals content resulting in increased metals concentrations. Unfortunately, we made no effort to record the reproductive status of the oysters used in this experiment and, therefore, cannot address this issue.
Whereas the genetic mechanisms that underlie these patterns are beyond the scope of this study, it is worth noting that molecular-level studies also support the hypothesis that heavy metals bioaccumulation is genetically determined in bivalve mollusks. For example, observations in two species of clams have shown that among-site differences in heavy metal concentrations are reflected in allele frequencies allele frequency
The percentage of a population of a species that carries a particular allele on a given chromosome locus. at 2 genetic markers genetic marker
A gene phenotypically associated with a particular, easily identified trait and used to identify an individual or cell carrying that gene. (phosphoclucomutase and glucosephosphate isomerase isomerase /isom·er·ase/ (i-som´er-as) a major class of enzymes comprising those that catalyze the process of isomerization.
n. ) and differences in protein level responses (metallothionein) to heavy metals challenges, strongly supporting the hypothesis that long-term exposure to heavy metals contamination can alter allele frequencies in bivalve mollusk mollusk: see Mollusca.
Any of some 75,000 species of soft-bodied invertebrate animals (phylum Mollusca), many of which are wholly or partly enclosed in a calcium carbonate shell secreted by the mantle, a soft populations (Moraga et al. 2002). Further, metallothionein genes, which encode (1) To assign a code to represent data, such as a parts code. Contrast with decode.
(2) To convert from one format or signal to another. See codec and D/A converter.
(3) The term is sometimes erroneously used for "encrypt. essential metal binding proteins that likely play a major role in metals detoxification Detoxification Definition
Detoxification is one of the more widely used treatments and concepts in alternative medicine. It is based on the principle that illnesses can be caused by the accumulation of toxic substances (toxins) in the body. (Cherian & Goyer 1978) have been cloned and characterized in Pacific oysters (Tanguy et al. 2001) and immunochemical assays im·mu·no·chem·i·cal assay
See immunoassay. for environmental contamination have been developed based on the idea that the levels of metallothionein in the gills and/or digestive gland digestive gland
A gland, such as the liver or pancreas, that secretes into the alimentary canal substances necessary for digestion. of Pacific oysters reflect the environmental availability of heavy metals through the induction of transcription (Boutet et al. 2002). Curiously, however, European flat oysters flat oysters
Ostrea spp. (Ostrea edulis) showed no such induction of metallothionein genes when exposed to copper and cadmium (Tanguy et al. 2003). As well, the somewhat misnamed mis·name
tr.v. mis·named, mis·nam·ing, mis·names
To call by a wrong name.
having an inappropriate or misleading name: heat shock protein heat shock protein
Any of a group of cellular proteins that are produced under conditions of heat stress and help to stabilize other cellular proteins exposed to high temperatures. gene family, Hsp70, which is involved in various stress responses (Feder & Hofmann 1999), shows altered patterns of expression in gill and digestive gland tissue of O. edulis in response to experimental cadmium exposure (Boutet et al. 2003). These more mechanistic mech·a·nis·tic
1. Mechanically determined.
2. Of or relating to the philosophy of mechanism, especially one that tends to explain phenomena only by reference to physical or biological causes. studies of how bivalves respond to heavy metals contamination and the relationship between environmental availability of metals and the expression of genes associated with detoxification also justify optimism that further work could identify molecular markers Molecular marker is a term with a number of uses. It is any kind of molecule indicating the existence of a chemical or physical process. In particular, in the fields of geology and astrobiology, biomarkers (also known as biosignatures) are sometimes understood as molecules that would allow direct selection on genotypes through marker-assisted selection. In fact, Tanguy et al. (2002), have showed that polymorphisms in the exons of metallothionein genes are related to heavy metal induced mortality in Pacific oysters, and it could be straightforward to extend this work to heavy metals bioaccumulation.
Regardless of the specific mechanisms that underlie the genetic correlations we observed, however, breeding programs A breeding program is the planned breeding of a group of animals or plants, usually involving at least several individuals and extending over several generations. Breeding programs are commonly employed in several fields where humans wish to manage the characteristics of their seeking to simultaneously improve growth and survival and reduce heavy metals should estimate and take into account the genetic correlation structure among these characters. Because genetically rigorous selective breeding of oysters is still in its infancy, and since the development of hatchery technology in the 1950s and its widespread commercialization in the 1970s, commercial growers have necessarily been making informal choices of which animals to use as broodstock, and these choices have, quite sensibly, emphasized yield--a combination of growth and survival. In addition, recently initiated formal selective breeding efforts, in response to growers' stated desires, have also emphasized improving yields (Langdon et al. 2003). If our finding that survival and yield are positively genetically correlated with copper and cadmium accumulation can be generalized to these semidomesticated populations of Pacific oysters, then these efforts are likely to also have raised the heavy metals content of farmed oysters as an indirect, correlated response.
Further research is needed to refine these estimates, and be cause genetic correlations are potentially variable among populations (Falconer & Mackay 1996), they must be estimated in the specific population of interest. Nonetheless, preliminary indications are that selective breeding to reduce heavy metals accumulation is possible, but unless the genetic correlations between heavy metals content and performance characters are explicitly taken into account in designing the selection scheme, undesirable correlated effects are likely. The genetic correlations we found between heavy metals content and performance traits are all moderate (r = 0.4-0.7), and if these estimates hold for other populations, properly designed selection strategies for multitrait improvement such as index selection or independent culling culling
removal of inferior animals from a group of breeding stock. The removal is premature, i.e. before completion of its life span, disposal of an animal from a herd or other group. (Falconer & Mackay 1996) should be able to produce strains with genetic improvement in performance and a reduction in heavy metals content. However, the rate of improvement is likely to be substantially slower than single-trait selection on any single character.
On a more cautionary note, designing a multitrait selection scheme is complex, and its implementation is a costly, long-term endeavor. For index selection, what is required is not only genetic-level information on the degree to which desirable traits are under additive genetic control, a reliable method for evaluating potential broodstock for all traits and the physical capacity to handle large numbers of genetically distinct families, but also appropriate weightings for the contributions of each trait to the selection index (Falconer & Mackay 1996). In most agricultural situations, these weightings are determined by the relative economical value of incremental Additional or increased growth, bulk, quantity, number, or value; enlarged.
Incremental cost is additional or increased cost of an item or service apart from its actual cost. improvement in each trait. Larger, more rigorous quantitative genetic analyses can provide better predictions of how much improvement is expected under different selection schemes, but not the information required to establish economical priorities. This must come from producers.
The authors thank Nicholas Sanchez and Machelle Nelson for their diligence in preparing and processing samples for heavy metals analysis and Alan Barton, Chris Emerson, Dave Jacobson, Sean Matson, Drew Mosher A mosher is a person who is crossed between goth/punk/skater they have long hair and listen to music like slipknot and metal music. Some people call them headbangers. At certain music shows they have something called a mosh pit, basically its a fight pit with loads of people bashing each other. , Ebru Onal, David Stick, and Dan Troop for their work in the hatchery and field. We also thank Dr. Chris Langdon for advice on experimental design and oyster husbandry husbandry
careful management of e.g. animals. Implies thrifty, humane, caring. See also animal husbandry. . This research was supported with funding from the USDA USDA,
n.pr See United States Department of Agriculture. Agricultural Research Service (CRIS Project #5358-31000-001-00D), from Anja Robinson Fellowship at Oregon State University's Hatfield Marine Science Center, and from a USDA CSREES CSREES Cooperative State Research, Education, and Extension Service (USDA) Special Grant to the Molluscan mol·lus·can also mol·lus·kan
Of or relating to the mollusks.
A mollusk. Broodstock Program (CRIS Project #ORE00359G).
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Adj. 1. estuarine - of or relating to or found in estuaries
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MARK D. CAMARA, (1) * STEPHEN M. GRIFFITH (2) AND SANFORD EVANS III (3)
(1) USDA, Agricultural Research Service, Hatfield Marine Science Center, 2030 SE Marine Science Dr., Newport, Oregon Newport is a city in Lincoln County, Oregon, United States. It was incorporated in 1882, though the name dates back to the establishment of a post office in 1868. As of the 2000 census, the city had a total population of 9,532, a growth of nearly 13% over its 1990 population. 97365; (2) USDA, Agricultural Research Service, Forage forage
Vegetable food, including corn and hay, of wild or domestic animals. Harvested, processed, and stored forage is called silage. Forage should be harvested in early maturity to avoid a decrease in protein and fibre content as crops mature. Seed Production Research Center, 3450 SW Campus Way, Corvallis, Oregon Corvallis (IPA: [ˌkɔɹ ˈvæl ɪs]) is a city located in central western Oregon, USA. It is the county seat of Benton CountyGR6 97331; (3) Oregon State University, Coastal Oregon Marine Experiment Station, Hatfield Marine Science Center, 2030 SE Marine Science Dr., Newport, Oregon
* Corresponding author. E-mail: Mark.Camar@oregonstate.edu Any use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the United States Department of Agriculture United States Department of Agriculture (USDA),
n.pr established in 1862, USDA is responsible for the safety of meat, poultry, and egg products. It conducts ongoing research in areas from human nutrition to new crop technologies and also helps ensure open or the Agricultural Research Service of any product or service to the exclusion of others that may be suitable.
TABLE 1. Mating design. Three large sires and three small sires were crossed with the same five dams, resulting in 30 matings, 26 of these matings were used in this experiment (X) and four did not produce enough progeny (-). Small Sires (Live Body Weight, g) Sire 1 Sire 2 Sire 3 Live Body Dam Weight (g) 61.59 70.34 73.82 1 144.01 X X X 2 147.58 X X -- 3 148.57 X X X 4 155.16 X X X 5 172.46 X X X Large Sires (Live Body Weight, g) Sire 4 Sire 5 Sire 6 Dam 138.22 138.56 158.35 1 X -- X 2 -- X X 3 X X X 4 X -- X 5 X X X TABLE 2. Characters measured in this experiment. Character Experimental Units Measured Description (units) Yield Lantern net compartments Wet weight of whole live oysters harvested from 50 seed(kg). Survival Lantern net compartments Proportion of seed surviving to harvest (none) Live Weight Individual oysters Whole weight of live animals (g) Dry Meat Weight Individual oysters Weight freeze-dried oyster meats (g) Copper Content Individual oysters Copper content/dry meat weight ([micro]g/g) Lead Content Individual oysters Lead content/dry meat weight ([micro]g/g) Zinc Content Individual oysters Zinc content/dry meat weight ([micro]g/g) Cadmium Content Individual oysters Cadmium content/dry meat weight ([micro]g/g) TABLE 3. Means, sample sizes and standard deviations of the eight characters measured. Variable N Mean Std Dev C.V. Yield 93 1.82 0.983 0.541 Survival 93 0.27 0.147 0.546 Live weight 493 140.79 43.892 0.312 Dry meat weight 497 5.39 2.098 0.389 Copper 495 35.01 12.255 0.350 Lead 495 0.18 0.136 0.748 Zinc 495 277.63 82.992 0.299 Cadmium 495 1.55 0.494 0.319 TABLE 4. Results from analyses of variance for each character. See text for explanation. P-values <0.05 are in bold face. Source of Variance DF Type III SS Type III MS F Prob >F Yield Blocks 1 0.7752 0.77520 2.43 0.1235 Sires 5 46.8509 9.37017 29.43 <.0001 Dams 4 8.1903 2.04757 6.43 0.0002 Sire x Dam 16 6.0890 0.38056 1.20 0.2955 Error 66 21.01657 0.31843 Survival Blocks 1 0.0238 0.02381 3.39 0.0702 Sires 5 1.0306 0.20612 29.33 <.0001 Dams 4 0.2316 0.05791 8.24 <.0001 Sire x Dam 16 0.1139 0.00712 1.01 0.4556 Error 66 0.46389 0.00703 Live weight Blocks 1 123.04795 123.04795 0.08 0.7841 Sires 5 23956.50601 4791.30120 2.93 0.0130 Dams 4 64894.84899 16223.71225 9.91 -0.0001 Sire x Dam 16 89198.41276 5574.90080 3.40 <.0001 Error 466 763080.97160 1637.51280 Dry meat weight Blocks 1 36.13681 36.13681 10.12 0.0016 Sires 5 64.83015 12.96603 3.63 0.0031 Dams 4 203.28882 50.82220 14.23 <.0001 Sire x Dam 16 204.36883 12.77305 3.58 <.0001 Error 470 1678.45899 3.57119 Copper Blocks 1 24.56160 24.56160 0.21 0.6473 Sires 5 3598.11827 719.62365 6.14 <.0001 Dams 4 5887.97669 1471.99417 12.56 <.0001 Sire x Dam 16 8499.23578 531.20224 4.53 <.0001 Error 468 54849.49127 117.19977 Lead Blocks 1 0.00006 0.00006 0.01 0.9409 Sires 5 1.02634 0.20527 19.28 <.0001 Dams 4 2.01972 0.50493 47.42 <.0001 Sire x Dam 16 1.07453 0.06716 6.31 <.0001 Error 468 4.98371 0.01065 Zinc Blocks 1 19438.59360 19438.59360 3.45 0.0639 Sires 5 39544.39210 7908.87840 1.40 0.2217 Dams 4 297046.80630 74261.70160 13.18 <.0001 Sire x Dam 16 309618.09620 19351.13100 3.43 <.0001 Error 468 2637827.76300 5636.38400 Cadmium Blocks 1 0.82398 0.82398 4.70 0.0307 Sires 5 13.73373 2.74675 15.65 <.0001 Dams 4 10.39830 2.59958 14.81 <.0001 Sire x Dam 16 15.31493 0.95718 5.45 <.0001 Error 468 82.12644 0.17548 TABLE 5. Heritabilities and genetic correlations for the eight traits measured in this study. Diagonal elements of the matrix (shaded) are the single-trait heritabilities (bootstrapped standard errors). Off-diagonal elements are Pearson correlation coefficients (r). Correlations above the diagonal are narrow-sense genetic correlations (family means correlations among the six paternal half-sib families). Those below the diagonal are broad sense genetic correlations (family means correlations among the 26 full-sib families). All estimates are based on block-adjusted data. Significance tests for heritabilities are based on the proportions of bootstrap re-samplings distributions that overlap zero; those for correlations are standard parametric hypothesis tests. Yield Survival Live Wt Yield 1.28 (0.185) 0.97 -0.07 **** **** ns Survival 0.99 1.29 (0.186) -0.24 **** **** ns Live Wt -0.48 -0.58 0.30 (0.099) ns ns **** Dry Meat Wt -0.70 -0.75 0.75 ns * * Copper 0.90 0.86 -0.19 *** ** ns Lead 0.33 0.26 0.25 ns ns ns Zinc 0.58 0.55 -0.1 ns ns us Cadmium 0.78 0.78 -0.43 * * ns Dry Meat Wt Copper Lead Yield -0.20 0.47 0.21 ns ** ns Survival -0.37 0.56 0.24 ** ** ns Live Wt 0.70 -0.17 -0.14 **** ns ns Dry Meat Wt 0.32 (0.104) -0.66 -0.13 **** **** ns Copper -0.47 0.42 (0.110) 0.25 ns **** ns Lead 0.38 0.58 0.94 (0.301) ns ns **** Zinc -0.21 0.81 0.57 ns * ns Cadmium -0.76 0.49 -0.19 * ns ns Zinc Cadmium Yield 0.18 0.46 ns ** Survival 0.29 0.56 ns *** Live Wt -0.17 -0.29 ns ns Dry Meat Wt -0.54 -0.66 *** **** Copper 0.85 0.70 **** **** Lead 0.14 0.27 ns ns Zinc 0.34 (0.099) 0.53 **** *** Cadmium 0.047 0.53 (0.118) ns **** **** P <0.001; *** P < 0.01; ** P <0.05; * P < 0.01; ns P > 0.1.