Rainbow Trout Early Life Stages Research Articles

Modelling effects of time-variable exposure to the pyrethroid beta-cyfluthrin on rainbow trout early life stages

BackgroundAvailable literature and regulatory studies show that the severity of effects of beta-cyfluthrin (a synthetic pyrethroid) on fish is influenced by the magnitude and duration of exposure. To investigate how the exposure pattern to beta-cyfluthrin (constant vs peak) may influence the response of the fish, we used a mechanistic effect model to predict the survival and growth of the rainbow trout over its early life stages (i.e. egg, alevin and swim-up fry). We parameterized a toxicokinetic–toxicodynamic (TKTD) module in combination with a dynamic energy budget model enabling us to describe uptake and elimination, as well as to predict the threshold concentration for survival and sublethal effects (feeding behaviour and growth). This effect model was calibrated using data from an early life stage experiment where trout was exposed to a constant concentration of cyfluthrin. The model was validated by comparing model predictions to independent data from a pulsed-exposure study with early life stages of rainbow trout.ResultsThe co-occurrence of effects on behaviour and growth raised the possibility that these were interrelated, i.e. impairment of feeding behaviour may have led to reduced food intake and slower growth. We, therefore, included ‘effect on feeding’ as mode of action in the TKTD module. At higher concentrations, the constant exposure led to death. The model was able to adequately capture this effect pattern in the calibration. The model was able to adequately predict the response of fish eggs, alevins and swim-up fry, from both the qualitative (response pattern) and quantitative points of view.ConclusionsSince the model was successfully validated, it can be used to predict survival and growth of early life stages under various realistic time-variable exposure profiles (e.g. profiles from FOCUS surface water modelling) of beta-cyfluthrin.

The ontogeny of regulatory control of the rainbow trout (Oncorhynchus mykiss) heart and how this is influenced by chronic hypoxia exposure

Salmonid embryos develop in cool waters over relatively long periods of time. Interestingly, hypoxic conditions have been found to be relatively common in some nesting sites (redds). The goals of this study were to determine the ontogeny of cardiac regulation in rainbow trout early life stages and how this is influenced by chronic hypoxia. The heart rate response to cholinergic and adrenergic receptor stimulation or inhibition was measured in individuals reared in normoxic (100% O(2) saturation) or hypoxic (30% O(2) saturation) conditions from fertilization to embryonic stages 22, 26 and 29, and larval stages 30 and 32. In normoxia, heart rate increased in response to β-adrenergic receptor stimulation (isoproterenol) as early as embryonic stage 22, and decreased with the antagonist propranolol after this stage. Cholinergic stimulation (acetylcholine) was ineffective at all stages, but atropine (acetylcholine antagonist) increased heart rate at larval stage 32. This demonstrates that cardiac β-adrenergic receptors are functional at early life stages, while cholinergic receptors are not responsive until after hatching. Collectively, embryos had cardio-acceleration control mechanisms in place just after the heartbeat stage, while cardio-inhibitory control was not functional until after hatching. Chronic hypoxia exposure triggered bradycardia, increased the response to adrenergic stimulation in embryos and larvae, and delayed the onset of cholinergic control in larvae. In non-motile stages, therefore, survival in chronic low oxygen may depend on the ability to alter the cardiac ontogenic program to meet the physiological requirements of the developing fish.

Effects of Maternal Versus Direct Exposure to Pulp and Paper Mill Effluent on Rainbow Trout Early Life Stages

The acute and chronic effects of secondary-treated effluent from a New Zealand pulp and paper mill were assessed using both long-term adult and early life stage (ELS) laboratory exposures of rainbow trout. The relative impact of maternal exposure versus ELS exposure was assessed by a comparison of directly exposed eggs and larvae with the eggs and larvae of exposed adult trout that were reared in reference water. Rainbow trout were exposed to a secondary-treated mixed thermomechanical/bleached kraft mill effluent at a concentration of 15% or to reference water from the egg through to 320-d-old juveniles. The 2 adult rainbow trout exposures were undertaken with nominal concentrations of 10% and 12% treated effluent, respectively. There was no marked effect of water hardening with 15% effluent on fertility or survival of eggs to 16 d. In a subsequent exposure (with hardening in reference water), no significant effects were found on mortality to hatch, time to hatch, length at hatch, mortality to swim-up, mortality to 320 d, or deformity rate at hatch. At experimental termination (320 d), direct-exposed juveniles had smaller livers and reduced condition factor, likely due to differences in food consumption. In 2 subsequent consecutive experiments, exposure of adult trout to 10% and 12% effluent for 2 mo, followed by incubation of the fertilized eggs in reference water, produced no impact on fertility, survival to hatch, survival to swim-up, or length and weight of fry at swim-up. Exposure of adult trout to 12% treated effluent for 8 mo prior to egg fertilization also did not result in differing rates of fertility, mortality to hatch or mortality to swim-up. However, the 8-mo maternal exposure did result in swim-up fry that were significantly shorter and weighed less than the reference swim-up fry. This difference was directly attributable to smaller eggs in the 8-mo-exposed female trout. These results demonstrate that this pulp and paper mill effluent is more likely to elicit indirect impacts on progeny size through chronic exposure of adults to effluent during gonadal recrudescence rather than through direct exposure of early life stages to effluent. Funding for this research was provided by the Arthur and Aenne Feindt Foundation of Germany, The Foundation for Research Science and Technology of New Zealand and by the Norske-Skog/Carter Holt Harvey Tasman Mill. The authors acknowledge the assistance of Megan Harris, Luca Chiaroni, Suzanne Lambie, Murray Smith, Nicola Marvin, Rob Hunter, Robert Donald, and Errol Cudby.

TCDD‐Like activity of 2,3,6,7‐tetrachloroxanthene in rainbow trout early life stages and in a rainbow trout gonadal cell line (RTG‐2)

AbstractFish in many areas are contaminated with 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) and related polychlorinated dibenzo‐p‐dioxin (PCDD), dibenzofuran (PCDF), and biphenyl (PCB) congeners. Other chemicals may also be present that act through the same mechanism. 2,3,6,7‐Tetrachloroxanthene (TCX) has been found to be an interference in PCDD and PCDF analyses and may occur in sediments near pulp and paper mills. However, the toxicology of TCX has not been studied in any species. This study sought to determine whether TCX causes TCDD‐like effects in two fish systems, rainbow trout early life stages and rainbow trout gonadal cells (RTG‐2) in culture. 2,3,6,7‐Tetrachloroxanthene caused rainbow trout sac fry mortality secondary to blue sac syndrome, identical to that caused by TCDD, and was similar in potency to TCDD for causing cytochrome P4501A mRNA induction in RTG‐2 cells and sac fry mortality in rainbow trout, with toxic equivalency factors of 1.09 to 2.29. These results suggest that TCX may pose a risk to feral fish in contaminated areas even at low concentrations.

Relative potencies of individual polychlorinated dibenzo‐p‐dioxin, dibenzofuran, and biphenyl congeners and congener mixtures based on induction of cytochrome P4501A mRNA in a rainbow trout gonadal cell line (RTG‐2)

AbstractCytochrome P450‐catalyzed enzyme activity in cell culture was investigated as a bioassay for 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) equivalents in environmental mixtures of polychlorinated dibenzo‐p‐dioxin (PCDD), dibenzofuran (PCDF), and biphenyl (PCB) congeners. A problem with the use of enzyme induction is that certain congeners are unable to induce P4501A enzyme activity to the same maximal level as TCDD. We sought to eliminate this problem by measuring mRNA induction rather than enzyme activity. Rainbow trout gonadal cells (RTG‐2) were exposed to PCDD, PCDF, and PCB congeners and congener mixtures, and induction of cytochrome P4501A mRNA was measured. A high level of induction in cells treated with only a medium change was seen and was due to a component of the fresh medium. 2,3,7,8‐Substituted PCDD and PCDF congeners and four non‐ortho‐substituted PCBs caused dose‐related induction of P4501A mRNA. Di‐ortho‐substituted PCBs did not induce P450 mRNA, but three mono‐ortho‐substituted PCBs caused significant induction. Toxic equivalency factors determined in RTG‐2 cells were generally higher than those in rainbow trout early life stages. Rainbow trout gonadal cell (RTG‐2) bioassay TCDD equivalents (TEqs) for three environmental extracts were lower than those predicted by addition of individual congener TEqs, and the synthetic congener mixture acted additively.

Toxic Equivalency Factors of Polybrominated Dibenzo-p-dioxin, Dibenzofuran, Biphenyl, and Polyhalogenated Diphenyl Ether Congeners Based on Rainbow Trout Early Life Stage Mortality

Polybrominated and polychlorinated biphenyls (PBBs/PCBs), dibenzo-p-dioxins (PBDDs/PCDDs), dibenzofurans (PBDFs/PCDFs), and diphenyl ethers (PBDEs/PCDEs) are persistent, lipophilic environmental contaminants that may pose a risk to fish early life stage survival. To determine this potential risk, a rainbow trout early life stage mortality bioassay was used in which the potency of individual polybrominated chemicals was compared to the potency of the most potent polychlorinated chemical in these classes, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Following injection of newly fertilized rainbow trout eggs, fish-specific toxic equivalency factors (TEFs) were calculated as the molar ratio of TCDD LD50 to brominated compound LD50. Signs of toxicity were identical to those produced by polychlorinated TCDD-like chemicals and included yolk sac edema, pericardial edema, multifocal hemorrhages, reduced growth, and craniofacial malformations. Polybrominated dibenzo-p-dioxins, dibenzofurans, and biphenyls exhibited decreased potency with increased bromine substitution. Only 2,3,7,8-TBDD was more potent than 2,3,7,8-TCDD, whereas other polybrominated dibenzo-p-dioxins were equipotent or less potent than identically substituted polychlorinated dibenzo-p-dioxins in this assay. Although two PBDF congeners were equipotent to identically substituted PCDFs, 2,3,7,8-TBDF was 9-fold more potent than 2,3,7,8-TCDF. Both 3,3′,4,4′-TBB and 3,3′,4,4′,5,5′-HxBB were 10-fold more potent than identically substituted polychlorinated biphenyls. The halogenated diphenyl ethers and di-ortho polybrominated biphenyls were inactive in this assay. Thus, in thisin vivoassay the polybrominated and polychlorinated TCDD-like chemicals were not always equally potent. To assess the risk posed by mixtures of these chemicals to feral fish populations, fish-specific TEFs for both polybrominated and polychlorinated chemicals should be used.

Additive Interactions between Pairs of Polybrominated Dibenzo-p-dioxin, Dibenzofuran, and Biphenyl Congeners in a Rainbow Trout Early Life Stage Mortality Bioassay

Use of fish-specific toxic equivalency factors (TEFs) to estimate the risk that exposure to polybrominated dibenzo-p-dioxins (PBDDs), dibenzofurans (PBDFs), and biphenyls (PBBs) pose to fish early life stage survival depends on validation of the hypothesis that these chemicals act additively to produce mortality. A rainbow trout early life stage bioassay was used to determine how pairs of PBDD, PBDF, and PBB congeners interact to produce 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-like toxicity associated with sac fry mortality. The congener pairs tested were 2,3,7,8-tetra- bromodibenzo-p-dioxin (2,3,7,8-TBDD)/1,2,3,7,8-pentabromodi- benzop-dioxin (1,2,3,7,8-PBDD); 2,3,7,8-TBDD/1,2,3,7,8-penta- bromodibenzofuran (1,2,3,7,8-PBDF); 1,2,3,7,8-PBDD/2,3,4,7,8-pentabromodibenzofuran (2,3,4,7,8-PBDF); and 2,3,4,7,8-PBDF/3,3′,4,4′-tetrabromobiphenyl (3,3′,4,4′-TBB). Graded doses of each congener alone, or graded doses of fixed ratios of paired congeners were injected into newly fertilized rainbow trout eggs. In all cases, interactions between congener pairs were additive as tested by a probit model. Isobolographic analysis also supported the hypothesis that the PBDD, PBDF, and PBB congeners act additively. Thus, the use of fish-specific TEFs to convert fish tissue concentrations of individual PBDD, PBDF, and PBB congeners to TCDD equivalents (TEs) and then adding the TEs contributed by the various congeners to give the total TCDD equivalents concentration (TEC) in the tissue is supported by these results. By comparing the TEC in feral fish eggs to the fish egg TCDD no-observed-effect level (NOEL) and lowest-observed-effect level (LOEL) for early life stage mortality, the risk that complex mixtures of these polybrominated chemicals in eggs pose to sac fry survival can be estimated.

TCDD-LIKE ACTIVITY OF 2,3,6,7-TETRACHLOROXANTHENE IN RAINBOW TROUT EARLY LIFE STAGES AND IN A RAINBOW TROUT GONADAL CELL LINE (RTG-2)

Fish in many areas are contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related polychlorinated dibenzo-p-dioxin (PCDD), dibenzofuran (PCDF), and biphenyl (PCB) congeners. Other chemicals may also be present that act through the same mechanism. 2,3,6,7-Tetrachloroxanthene (TCX) has been found to be an interference in PCDD and PCDF analyses and may occur in sediments near pulp and paper mills. However, the toxicology of TCX has not been studied in any species. This study sought to determine whether TCX causes TCDD-like effects in two fish systems, rainbow trout early life stages and rainbow trout gonadal cells (RTG-2) in culture. 2,3,6,7-Tetrachloroxanthene caused rainbow trout sac fry mortality secondary to blue sac syndrome, identical to that caused by TCDD, and was similar in potency to TCDD for causing cytochrome P4501A mRNA induction in RTG-2 cells and sac fry mortality in rainbow trout, with toxic equivalency factors of 1.09 to 2.29. These results suggest that TCX may pose a risk to feral fish in contaminated areas even at low concentrations.

Interactions of Polychlorinated Dibenzo- p-dioxin, Dibenzofuran, and Biphenyl Congeners for Producing Rainbow Trout Early Life Stage Mortality

Fish-specific toxic equivalency factors (TEFs), which relate the toxic potency of polyhalogenated aromatic hydrocarbons (PHAHs) to 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) based on the endpoint of early life stage mortality, have been used in assessing the risk to fish early life stage survival of complex mixtures of PHAHs in feral fish eggs. Use of TEFs assumes that PHAH congeners act additively. However, this has not been unequivocally determined. Isobolograms and a probit model were used to assess the validity of the additivity assumption by determining the significance of interactions between pairs of polychlorinated dibenzo- p-dioxin (PCDD), dibenzofuran (PCDF), and biphenyl (PCB) congeners when injected into newly fertilized rainbow trout eggs in ratios bracketing those found in feral lake trout eggs from the Great Lakes. The majority of congener pairs tested acted additively in causing rainbow trout early life stage mortality: [1,2,3,7,8-pentachlorodibenzo- p-dioxin (1,2,3,7,8-PCDD)/TCDD]; [2,3,4,7,8-pentachlorodibenzofuran (2,3,4,7,8-PCDF)/1,2,3,7,8-PCDD]; (2,3,4,7,8-PCDF/TCDD), (2,3,7,8-tetrachlorodibenzofuran/2,3,4,7,8-PCDF); [3,3′,4,4′-tetrachlorobiphenyl (PCB 77)/ 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126)]; [2,3,3′,4,4′-pentachlorobiphenyl (PCB 105)/TCDD]; (2,2′,4,4′,5,5′-hexachlorobiphenyl/TCDD); (PCB 105/PCB 126); and (2,3′,4,4′,5-pentachlorobiphenyl/PCB 126). The only pairs showing evidence of a statistically significant interaction that deviated from additivity were (TCDD/PCB 77) and (TCDD/PCB 126). Taken together, these results suggest that the use of fish-specific TEFs to determine TCDD equivalents contributed by individual congeners in a fish egg sample and then adding these TCDD equivalents to determine the total amount contributed by all congeners may not exactly predict the mortality risk posed to fish early life stages by the mixture of TCDD-like congeners in the eggs. However, the relatively small deviations from additivity in the rainbow trout sac fry mortality test (1- to 4-fold) are less than traditional uncertainty factors used in noncancer risk assessments (10-fold/factor) and are not sufficient to warrant a change away from the additivity assumption in assessing the risk to fish early life stage mortality posed by TCDD and related compounds in eggs.

Effects of octamethylcyclotetrasiloxane (OMCTS) on freshwater and marine organisms

AbstractThe toxicity of octamethylcyclotetrasiloxane (OMCTS) to representative freshwater and marine fish and invertebrates was investigated. Testing procedures followed Toxic Substance Control Act (TSCA) guidelines with chemical‐specific adaptations as presented in the OMCTS Testing Consent Order (Docket OPTS‐42071A). The physicochemical properties and behavior of OMCTS (i.e., high volatility, low water solubility) precluded the use of conventional experimental practices and exposure systems. Procedures and systems developed during these investigations provided a mechanism that produced exposure levels equal to the maximum achievable (i.e., “functional”) solubility of OMCTS in natural dilution waters. The toxicant delivery systems and exposure chambers were designed to minimize volatilization by elimination of the air/water interface. The flow‐through systems maintained consistent exposure concentrations and adhered to U.S. Environmental Protection Agency (EPA) Guideline test performance criteria. The “functional” water solubility of OMCTS in freshwater and seawater ranged from 14 to 30 μg/L and from 6.0 to 9.0 μg/L, respectively. Functional water solubility appeared to vary slightly with test conditions and dilution water characteristics. Continuous exposures of 2 to 93 d were conducted during these investigations with daphnids (Daphnia magna), rainbow trout (Oncorhynchus mykiss), mysids (Mysidopsis bahia), and sheepshead minnow (Cyprinodon variegatus). The rainbow trout was determined to be the most sensitive species to OMCTS (14‐d LC50 = 10 μg/L). At levels equal to the functional water solubility, OMCTS was not acutely toxic to D. magna, mysids, or sheepshead minnow. The survival of D. magna was reduced by 16%, relative to the control organisms, after 21‐d exposures to 15 μg/L OMCTS; exposure to 7.9 μg/L OMCTS or less had no effect on daphnid survival or reproduction. No toxicity was observed at the highest concentration tested in a 93‐d exposure of rainbow trout early life stages. The no‐observed‐effect concentration for this study was 4.4 μg/L, the same as determined in a 14‐d extended acute study.

Toxic equivalency factors of polychlorinated dibenzo- p-dioxin, dibenzofuran and biphenyl congeners based on early life stage mortality in rainbow trout ( Oncorhynchus mykiss)

Toxic equivalency factors (TEFs), which relate the potency of individual polychlorinated dibenzo- p-dioxin (PCDD), dibenzofuran (PCDF), and biphenyl (PCB) congeners to 2,3,7,8- tetrachlorodibenzo- p-dioxin (TCDD), are used to assess the risk to fish early life stage development posed by complex mixtures of these congeners in eggs. Newly fertilized rainbow trout ( Oncorhynchus mykiss) eggs were injected with graded doses of 5 PCDD, 4 PCDF or 4 nonortho substituted PCB congeners, and sac fry mortality was used to determine TEFs. Potencies of non-ortho substituted PCBs in causing early life stage mortality were much lower than expected based on Ah receptor binding affinities in mammals and 4 mono-ortho and 5 di-ortho substituted PCB congeners did not cause rainbow trout early life stage mortality at doses of 24 300–130 000 ng/g egg. To determine if increased elimination of PCBs, relative to PCDDs and PCDFs, was responsible for the lower toxic potency of PCBs in fish compared to mammals, PCDD, PCDF and PCB congeners were injected into newly fertilized rainbow trout eggs and the percent dose remaining 35 days later at the sac fry stage of development was determined. The percent dose of various PCB congeners remaining in sac fry (62–88%) was similar to that of PCDD and PCDF congeners (78–91%), indicating that increased elimination is not responsible for the extremely low potency of the non-ortho substituted PCB congeners or for the failure of the mono- and di-ortho substituted PCB congeners to cause rainbow trout early life stage mortality.

A review of the aquatic ecotoxicology of polychlorinated dibenzo‐p‐dioxins and dibenzofurans

AbstractThis paper reviews published studies on polychlorinated dibenzo‐p‐dioxins and polychlorinated dibenzofurans that are relevant to an assessment of their aquatic ecotoxicology. The available data suggest that laterally substituted congeners containing altogether 4,5, or 6 chlorine atoms are highly toxic, particularly to the early life stages of fish, with reported effect concentrations in the ng L1 range. These congeners are also the most readily bioaccumulated.An aquatic toxicity threshold concentration of 0.011–0.038 ng L−1, applicable to natural ecosystems, was determined for 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (or for mixtures of congeners expressed as 2,3,7,8‐TCDD equivalents). This threshold corresponds to the no observed effect concentration/lowest‐observed effect concentration determined for mortality, growth, and behavioral effects seen in rainbow trout early life stages, exposed to 2,3,7,8‐TCDD in a flow‐through system over a 28‐day period, followed by 28 days of depuration.An investigation was also made into the potential for using mammalian‐derived toxic equivalency factors (TEFs) in aquatic ecosystems. This revealed that such an approach may underestimate the aquatic toxicity of some congeners, and that the use of organism‐specific TEFs may be more appropriate. © by John Wiley & Sons, Inc.

EFFECTS OF OCTAMETHYLCYCLOTETRASILOXANE (OMCTS) ON FRESHWATER AND MARINE ORGANISMS

The toxicity of octamethylcyclotetrasiloxane (OMCTS) to representative freshwater and marine fish and invertebrates was investigated. Testing procedures followed Toxic Substance Control Act (TSCA) guidelines with chemical-specific adaptations as presented in the OMCTS Testing Consent Order (Docket OPTS-42071A). The physicochemical properties and behavior of OMCTS (i.e., high volatility, low water solubility) precluded the use of conventional experimental practices and exposure systems. Procedures and systems developed during these investigations provided a mechanism that produced exposure levels equal to the maximum achievable (i.e., “functional”) solubility of OMCTS in natural dilution waters. The toxicant delivery systems and exposure chambers were designed to minimize volatilization by elimination of the air/water interface. The flow-through systems maintained consistent exposure concentrations and adhered to U.S. Environmental Protection Agency (EPA) Guideline test performance criteria. The “functional” water solubility of OMCTS in freshwater and seawater ranged from 14 to 30 μg/L and from 6.0 to 9.0 μg/L, respectively. Functional water solubility appeared to vary slightly with test conditions and dilution water characteristics. Continuous exposures of 2 to 93 d were conducted during these investigations with daphnids (Daphnia magna), rainbow trout (Oncorhynchus mykiss), mysids (Mysidopsis bahia), and sheepshead minnow (Cyprinodon variegatus). The rainbow trout was determined to be the most sensitive species to OMCTS (14-d LC50 = 10 μg/L). At levels equal to the functional water solubility, OMCTS was not acutely toxic to D. magna, mysids, or sheepshead minnow. The survival of D. magna was reduced by 16%, relative to the control organisms, after 21-d exposures to 15 μg/L OMCTS; exposure to 7.9 μg/L OMCTS or less had no effect on daphnid survival or reproduction. No toxicity was observed at the highest concentration tested in a 93-d exposure of rainbow trout early life stages. The no-observed-effect concentration for this study was 4.4 μg/L, the same as determined in a 14-d extended acute study.

Sensitivity of rainbow trout early life stages to nickel chloride

AbstractFour acute tests (96‐h) with juvenile fish and four early life stage tests with embryos and larvae were completed with rainbow trout (Salmo gairdneri). Ninety‐six‐hour flow‐through LC50 values for juveniles ranged from 8.1 to 10.9 mg/L nickel. Two early life stage tests were started with newly fertilized eggs, one test was started with eyed eggs and one test was started with pre‐swim‐up larval fish. No observed effect levels (NOEL), the highest nickel concentration without statistically significant adverse effects, for the two tests with newly fertilized eggs were less than 35 and 35 μg/L. The NOEL for the tests starting with eyed eggs and larval fish was 134 μg/L nickel. Early life stages were most sensitive when newly fertilized eggs were initially exposed, followed in sensitivity by eyed eggs, larval fish and juvenile fish.