Freshwater Amphipod Hyalella Azteca Research Articles

Single-Walled Carbon Nanotubes Toxicity to the Freshwater Amphipod Hyalella Azteca: Influence of to the Freshwater Amphipod Sediment and Exposure Duration.

Carbon nanomaterials are present in various industrial applications and therefore their release into the environment including freshwater ecosystem is expected to increase. The aim of the present study was to investigate the influence of several parameters on the toxicity of single-walled carbon nanotubes (SWCNT) to the freshwater amphipod, Hyalella azteca. The effect of period of exposure, sediment presence and possible impurities released during SWCNT preparation on survival and/or growth of such organism was evaluated. We measured a reduction of survival at concentrations ranging from 10 to 40 mg/L after 96-h exposure, while no mortality was observed with the same concentrations and in the presence of artificial sediment after 14 days of exposure. It is possible that SWCNT are adsorbed on the organic matter from the artificial sediment leading to a decrease of SWCNT bioavailability. The survival and growth toxicity tests revealed a stronger effect at 28 days compared to the 14 days of exposure, and full mortality of organisms at 1000 mg/L for both exposure times. The presence of SWCNT in the gut of survived organisms was observed. The present study demonstrates that the interaction with sediment should be considered when carbon nanotubes toxicity through water exposure is investigated.

Development of a biopolymer nanoparticle-based method of oral toxicity testing in aquatic invertebrates

Aquatic toxicity testing generally focuses on the water absorption/dermal route of exposure to potential toxic chemicals, while much less work has been done on the oral route of exposure. This is due in part to the difficulties of applying traditional oral toxicity testing to aquatic environments, including the tendency for test chemicals to dissolve into water. The use of biopolymer nanoparticles to encapsulate test chemicals onto food to prevent dissolution is one solution presented herein. The biopolymers zein and chitosan were explored for their previously known nanoparticle-forming abilities. Nanoparticles containing the test chemical rhodamine B were formed, applied as films to coat food, and then fed to the test organism, the freshwater amphipod Hyalella azteca. In feeding trials both zein and chitosan nanoparticles showed a significantly lower release rate of rhodamine B into water than food dyed with rhodamine B without biopolymer nanoparticles. Zein nanoparticles also showed better retention ability than chitosan nanoparticles. Both kinds of nanoparticles showed no significant effect on the survival, growth, or feeding behavior of H. azteca. Thus these biopolymers may be an effective system to encapsulate and deliver chemicals to aquatic invertebrates without interfering with common toxicity assessment endpoints like survival and growth.

Predator cues alter habitat use by the amphipod Hyalella azteca (Saussure)

The abundance and distribution of aquatic mesograzers may be regulated by both top-down (i.e., predator-mediated) and bottom-up (i.e., producer-mediated) effects. Under predation by fish, these herbivores may experience differential survivorship among different types of resource patches. Prey may attempt to maximize fitness by integrating information on predation risk and patch quality into foraging decisions. The freshwater amphipod Hyalella azteca occupies mats of the toxic cyanobacterium Lyngbya wollei and the green alga Rhizoclonium hieroglyphicum in lotic water bodies throughout the southeastern USA. We tested the hypotheses that Lyngbya is an effective refuge from Bluegill Sunfish (Lepomis macrochirus) predation and that predator cues modify habitat selection by amphipods. In no-choice assays, amphipods exposed to fish predation showed higher survivorship on Lyngbya than on Rhizoclonium. In choice assays, we observed greater proportions of amphipods on Lyngbya in tanks containing either predators or waterborne predator cues compared to control tanks containing only freshwater. These results suggest that Lyngbya is an effective refuge from predation for amphipods. Furthermore, predatory fish may indirectly influence the relative abundance of algae and cyanobacteria by reducing amphipod abundance on highly palatable species and restricting these mesograzers to less palatable species.

First Record of the Intermediate Host ofPseudocorynosoma constrictumVan Cleave, 1918 (Acanthocephala: Polymorphidae) in Central Mexico

ABSTRACT: Pseudocorynosoma constrictum Van Cleave, 1918 (Polymorphidae) is an endoparasite that infects a variety species of waterfowl from North America. Specimens of P. constrictum were recovered in central Mexico from 7 species of definitive host as well as from the freshwater amphipod Hyalella azteca, its intermediate host. In total, 69 amphipods were infected with 15 acanthella and 58 cystacanths. Morphologically, the adults and cystacanths of P. constrictum possess triangular spines covering most of the anterior part of the trunk, they have a slight constriction separating the anterior and posterior regions of the trunk, and they have an ovoid or cylindrical proboscis with a slightly swollen region covered with 16 longitudinal rows of 10 hooks each. Sequences of the mitochondrial coding gene cytochrome c oxidase were generated for 21 samples of P. constrictum (14 adults, 3 acanthella, and 4 cystacanths). The genetic divergence estimated among specimens was very low, ranging from 0 to 3%. All these s...

An effects addition model based on bioaccumulation of metals from exposure to mixtures of metals can predict chronic mortality in the aquatic invertebrate hyalella azteca

Chronic toxicity tests of mixtures of 9 metals and 1 metalloid (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Tl, and Zn) at equitoxic concentrations over an increasing concentration range were conducted with the epibenthic, freshwater amphipod Hyalella azteca. The authors conducted 28-d, water-only tests. The bioaccumulation trends changed for 8 of the elements in exposures to mixtures of the metals compared with individual metal exposures. The bioaccumulation of Co and Tl were affected the most. These changes may be due to interactions between all the metals as well as interactions with waterborne ligands. A metal effects addition model (MEAM) is proposed as a more accurate method to assess the impact of mixtures of metals and to predict chronic mortality. The MEAM uses background-corrected body concentration to predict toxicity. This is important because the chemical characteristics of different waters can greatly alter the bioavailability and bioaccumulation of metals, and interactions among metals for binding at the site of action within the organism can affect body concentration. The MEAM accurately predicted toxicity in exposures to mixtures of metals, and predicted results were within a factor of 1.1 of the observed data, using 24-h depurated body concentrations. The traditional concentration addition model overestimated toxicity by a factor of 2.7.

Cadmium bioavailability to Hyalella azteca from a periphyton diet compared to an artificial diet and application of a biokinetic model

Differences between the bioavailability of cadmium in a periphyton diet and an artificial laboratory diet (TetraMin®) have important consequences for predicting bioaccumulation and toxicity in the freshwater amphipod Hyalella azteca. The assimilation efficiency (AE) of Cd was compared between periphyton and TetraMin® at low (1510 and 358nmol/g ash-free dry mass respectively) and chronically lethal (31,200 and 2890nmol/g ash-free dry mass respectively) Cd concentrations and in fresh and dry forms using a 109Cd radiotracer pulse-chase feeding technique. Assimilation efficiency of Cd from periphyton (AE=3–14%) was lower than that for TetraMin® (AE=44–86%) regardless of Cd concentration or food form. Ingestion rate (IR) was lower for dry than fresh forms of periphyton (0.042 and 0.16g AFDM/g H. azteca/day respectively) and TetraMin® (0.19 and 0.87AFDM/g H. azteca/day respectively) and depuration rate (ke) did not differ statistically with food type, form or Cd concentration (0.032–0.094d−1). Biokinetic models with parameters of AE, IR and ke were used to estimate bioaccumulation from the separate food types. These estimates were compared to those from an independent chronic Cd saturation bioaccumulation model. While the model estimates did not concur, a sensitivity analysis indicated that AE and IR were the most influential biokinetic model parameters for Cd in periphyton and TetraMin® respectively. It was hypothesized that AE was underestimated for Cd in periphyton due to a non-adapted gut enzyme system and IR was overestimated for Cd in TetraMin® due to an initial rapid ingestion phase in H. azteca's feeding habits. This research demonstrated the importance of using ecologically relevant food types in laboratory experiments and verifying acute biokinetic model predictions of dietary metal contribution with those derived from a chronic exposure which is more representative of a field exposure scenario.

Interactive effects of phosphorus and copper on Hyalella azteca via periphyton in aquatic ecosystems

This research examined the interaction between dissolved copper and phosphorus, with respect to their effects on the freshwater amphipod Hyalella azteca feeding on periphyton. Field-collected periphyton communities were exposed to different nutrient and metal conditions in indoor recirculating streams. H. azteca were then exposed to water and periphyton from these streams. There was rapid Cu accumulation by periphyton but the total Cu concentration of periphyton was not directly related to dissolved P. In terms of H. azteca growth, an interactive effect was found between Cu and P as growth was reduced more than expected in the low Cu-high P treatment. Our data suggest that eutrophic conditions result in greater Cu toxicity to benthic macroinvertebrates at lower metal concentrations, likely due to higher assimilation efficiency of dietary Cu from periphyton incubated under eutrophic conditions. These results imply that non-additive interactions between multiple stressors may cause ecosystem effects as detected in standard laboratory bioassays conducted under controlled conditions.

Phylogenetic analysis ofHyalellacolonization in lakes recovering from acidification and metal contamination

The freshwater amphipod Hyalella azteca (Saussure, 1858) is common throughout North America and is a popular organism for toxicity tests and assessment of an ecosystem’s health. However, recent studies suggest that this “species” may actually be a number of closely related species, possibly with distinct habitat requirements. The region in and around Sudbury, Ontario, has many lakes recovering from acidification and metal contamination with Hyalella slowly recolonizing the area. Analyzing mitochondrial cytochrome c oxidase I (COI) sequences, we find two major groups of Hyalella: one group associated with recolonization of the central, historically more contaminated set of lakes and a second group associated with the more distant, less impacted, lakes. Morphologically, these inner city amphipods are significantly larger than those observed in lakes farther away from the city. This study may provide a foundation for a better understanding of Hyalella species complex, as well as colonization routes, toxicological sensitivities, habitat requirements, and dispersal capabilities.

Modeling chronic dietary cadmium bioaccumulation and toxicity from periphyton to Hyalella azteca

A chronic (28-d) Cd saturation bioaccumulation model was developed to quantify the Cd contribution from a natural periphyton diet to Cd in the freshwater amphipod Hyalella azteca. Bioaccumulation was then linked to chronic toxic effects. Juvenile H. azteca were exposed to treatments of Cd in water (3.13-100 nmol/L nominal) and food (389-26,300 nmol/g ash-free dry mass). Cadmium bioaccumulation, survival, and growth were recorded. Dietary Cd was estimated to contribute 21 to 31, 59 to 94, and 40 to 55% to bioaccumulated Cd in H. azteca exposed to treatments of Cd primarily in water, food, and food + water, respectively. Survival as a function of Cd lethal body concentration (679 nmol/g; 95% confidence limits, 617-747) was the most robust endpoint. Body concentration integrated all exposure routes. Based on the lethal body concentration, dietary Cd was predicted to contribute markedly (26-90%) to Cd in H. azteca. Cadmium concentration and food nutritional quality (biomass, chlorophyll a, total lipid, fatty acids, total protein) had no effect on H. azteca nutritional quality (total lipid, fatty acids, total protein) but did influence H. azteca dry weight. This research highlighted the importance of including a dietary component when modeling chronic effects of Cd and when refining endpoints for use in ecological risk assessment and water quality guidelines.

Survival and precopulatory guarding behavior of Hyalella azteca (Amphipoda) exposed to nitrate in the presence of atrazine

Nitrate is one of the most commonly detected contaminants found in aquatic systems with other pesticides such as atrazine. The current study examined potential combined effects of nitrate and atrazine on adults of the freshwater amphipod Hyalella azteca, using survival and precopulatory guarding behavior as toxic endpoints. Although significant differences in acute toxicity with nitrate alone and in binary combination with atrazine (200 µg/L) in water-only tests were not consistently observed for each time point, potential biologically relevant trends in the data were observed. Posttest growth and behavioral observations (10-day period) conducted after 96-hour exposure suggested that atrazine and nitrate at these concentrations did not result in delayed effects on H. azteca. However, when test conditions were modified from standard toxicity tests by feeding amphipods, nitrate was found to be more toxic, with a reduction in median lethal concentration (LC50) values of approximately 80%. We also demonstrated that nitrate exhibits a dose-response effect on precopulatory guarding behavior of H. azteca, suggesting that reproductive effects may occur at environmentally relevant concentrations.

An assessment of Hyalella azteca burrowing activity under laboratory sediment toxicity testing conditions

Burrowing of the freshwater amphipod Hyalella azteca was evaluated under laboratory conditions similar to those recommended for standard sediment toxicity testing in Canada (EPS 1/RM/33; Environment Canada, 1997) and the United States (EPA/600/R-99/064; US EPA, 2000). Sediment type, time of day (light versus dark), size of animal, and the presence or absence of food were varied to assess their effects on burrowing activity. Hyalella azteca were found to burrow rapidly in fine, organic-rich sediments, but were slower to burrow in a sandy sediment. There was no increase in the number of animals occupying the sediment surface of a fine, organic-rich sediment after 4 h of darkness compared to the previous 4 h of light. Over a 9- to 10-d duration, a higher percentage of animals occupied the surface of the sandy sediment. The addition of food promoted burrowing in sandy sediment, as did using smaller animals. Overall, longer-duration tests involving older animals and coarse sediments may require formal observation to confirm burrowing and ensure adequate sediment exposure. The addition of food during a test may promote the burrowing of larger animals in coarse sediments, but may not be necessary in field-collected sediments that are not excessively sandy.

Chronic toxicity of the synthetic hormone 17α‐Ethinylestradiol to Chironomus tentans and Hyalella azteca

The chronic toxicity of the synthetic hormone 17alpha-ethinylestradiol (EE2) was investigated in two benthic invertebrates, the midge Chironomus tentans and the freshwater amphipod Hyalella azteca, in life-cycle water-only assays. In C. tentans, a 50% decrease in emergence was observed at a concentration of 1.5 mg/L; emergence was a more sensitive endpoint than survival, growth, or biomass. Reproduction was not significantly affected by EE2 exposure until a concentration of 3.1 mg/L, where emergence, and therefore reproduction, did not occur. In contrast, reproduction was the most sensitive endpoint in H. azteca (50% decrease in reproduction observed at a concentration of 0.36 mg/L). The sensitivity of the F1 generation to EE2 was also investigated with H. azteca, but was not different from the F0 generation. The data from the present study were combined with those from previous 10-d toxicity assays, to derive acute to chronic toxicity ratios (ACRs) for EE2. The ACRs calculated for EE2 were 13 for C. tentans and 16 for H. azteca, indicating that the application factors currently used in ecological risk assessment for the derivation of chronic toxicity are protective and conservative for these organisms. The results of the present study suggest that chronic toxicity was not mediated by disruption of endocrine pathways. Using a hazard quotient approach, the risk associated with sublethal exposure to EE2 was <<1 for H. azteca and C. tentans, indicating that adverse effects are not expected, and that environmental exposure to EE2 likely poses a low risk to benthic invertebrates.

Toxicity of human pharmaceuticals and personal care products to benthic invertebrates

Despite concerns about potential risks associated with the presence of pharmaceuticals and personal care products (PPCPs) in the environment, few toxicological data address the effects of these compounds. In aquatic systems, which often represent the final repository for PPCPs, increasing toxicological information regarding aquatic biota is improving our capacity to assess potential risks. However, responses of key biota, such as benthic invertebrates, have not been investigated as widely. In the present study, we examined the toxicity of four PPCPs -- the lipid regulator atorvastatin (ATO), the antiepileptic drug carbamazepine (CBZ), the synthetic hormone 17alpha-ethinylestradiol (EE(2)), and the antimicrobial triclosan (TCS) -- to the midge Chironomus tentans and the freshwater amphipod Hyalella azteca in 10-d waterborne exposures. The toxicity of the four compounds varied between 0.20 and 47.3 mg/L (median lethal concentration), with a relative toxicity ranking of TCS > EE(2) > ATO > CBZ. Hyalella azteca was more sensitive than C. tentans to these compounds. The toxicity data were used in a hazard quotient approach to evaluate the risk posed by the four PPCPs to benthic invertebrates and other aquatic organisms. For each compound, a hazard quotient was calculated by dividing the lowest toxicity value by the highest exposure value found in the literature, to which an uncertainty factor was applied. With hazard quotients of 3.55 to 11.5, we conclude that potential risks exist toward benthic invertebrates for the toxicity of TCS and CBZ and that further investigations of these compounds are required to characterize more completely the risks to benthic organisms. In contrast, our data also indicate that considering the low concentrations currently detected in the environment, ATO and EE(2) pose negligible risks to benthic invertebrates.

Toxicity of a cadmium‐contaminated diet to Hyalella azteca

Four- and 10-week chronic toxicity tests were conducted using the freshwater amphipod Hyalella azteca and Cd-contaminated Chlorella sp. as a food source. Chlorella sp. was cultured in various Cd concentrations, filtered from solution, rinsed, dried, and ground into food flakes for the H. azteca. Unlike Cd toxicity from water sources, growth was found to be a more sensitive toxicological endpoint than survival, with calculated 50 and 25% effect concentrations (EC50s and EC25s, respectively) of 5.43 and 2.82 nmol/g, respectively, for Cd measured in food. Based on the regression of Cd in Chlorella sp. against Cd in filtered culture medium, the EC50 and EC25 corresponded to dissolved Cd concentrations of 11.30 and 5.09 nmol/L, respectively. Little or no bioaccumulation of Cd was found in the tissues of H. azteca that were fed contaminated food. These results demonstrate an apparent toxicological effect (either direct or indirect) of Cd-contaminated Chlorella sp. to H. azteca that is not associated with Cd accumulation. Toxicity of Cd-contaminated Chlorella sp. differs from waterborne Cd toxicity both in terms of the most sensitive endpoint (growth vs survival) and the relationship between toxicity and bioaccumulation. Unlike Cd toxicity through water exposure, Cd bioaccumulation by H. azteca cannot, therefore, be used to infer toxicity of Cd in a diet of Chlorella sp. Although the concentration of Cd in the algal culture medium that ultimately reduced growth of H. azteca in the present study was higher than Cd in water, which caused mortality to H. azteca in water-only tests during previous studies, further research regarding the contribution of dietary Cd to overall Cd toxicity is needed to verify that water-quality guidelines and risk assessments based on water-only exposures are fully protective.

Effect of a mixture of seven pharmaceuticals on Hyalella azteca over multiple generations

A mixture of seven common pharmaceutical agents (acetaminophen, diclofenac, gemfibrozil, ibuprofen, naproxen, salicylic acid, and triclosan) was tested for its effects on the freshwater amphipod Hyalella azteca over three generations. The target concentration of each chemical (100 ng l −1) was representative of the upper range observed for these substances in Canadian fresh waters, except in the immediate vicinity of effluent discharges. No statistically significant effects were observed on survival, mating, body size or reproduction. The sex ratio changed slightly to 17% more males. The seven pharmaceuticals tested do not appear to be substances of major concern for Hyalella in most Canadian fresh waters, but significant impacts might be observed in areas closer to effluent discharges.

Bioconcentration and depuration of copper, cadmium, and zinc mixtures by the freshwater amphipod Hyalella azteca

The uptake and elimination of copper (Cu), cadmium (Cd), and zinc (Zn) by the amphipod Hyalella azteca during exposure to the metals singly and in various combinations was examined in controlled laboratory experiments. In single metal exposures the accumulation of all metals was rapid and increased with exposure time. Copper elimination was slower compared to that for zinc and for cadmium no elimination was detected after 5 days in clean water. In the two-metal mixtures it appears that the presence of one metal influenced the bioconcentration of the other, since the bioconcentration factor (BCF) for copper was higher in the presence of cadmium than in the presence of zinc and in the case of cadmium, the decrease of K 1 values from cadmium single exposure to the binary and tertiary mixtures suggests possible inhibition of cadmium uptake by the other metals. In the case of the three-metal mixture the situation is less clear, with both increased and decreased BCFs recorded, in comparison to single-metal and two-metal mixtures, suggesting both stimulation and inhibition of metal accumulation.

Joint Toxicity of Cadmium and Phenanthrene in the Freshwater Amphipod Hyalella azteca

The joint toxicity of combined metals and polynuclear aromatic hydrocarbons is poorly understood and may deviate from the summed concentration responses of the individual pollutants. The freshwater amphipod Hyalella azteca was exposed to sediment-amended Cd and phenanthrene (Phen) individually and in combination using United States Environmental Protection Agency 10-day sediment toxicity bioassays with lethality and growth end points. The lethal joint toxicity of Cd and Phen was investigated separately in 24-, 48-, and 72-hour aqueous exposures. In sediment exposures, a sublethal concentration of Phen (144 mg kg(-1)) in combination with Cd increased mortality across a range of Cd concentrations and decreased the 10-day LC50 for Cd from 523 mg kg(-1) (461 to 588, 95% confidence interval [CI]) to 263 mg kg(-1) (214 to 312, 95% CI). In contrast, sublethal concentrations of Phen had no effect on the lethal toxicity of Cd in aqueous exposures. Combined sediment-amended Cd and Phen acted independently on growth rate. Rate decreases were driven primarily by Cd. Our findings indicated that association with sediment influences the joint toxicity of Cd and Phen. Thus, mixtures of Cd and Phen may cause synergistic or independent toxicity in H. azteca depending on the end point investigated and the experimental protocol employed. As an implication of these results, the interpretation of standardized toxicity bioassays, including whole-effluent toxicity tests and single-compound toxicity tests, must be made with caution. These assessment protocols may underestimate potentially hazardous mixture effects in sediment environments. Therefore, risk assessment protocols for environments containing metal-PAH mixtures must include robust methods that can detect possible interactive effects among contaminants to optimize environmental protection.

Lac Dufault sediment core trace metal distribution, bioavailability and toxicity to Hyalella azteca

To determine changes in metal distribution, bioavailability and toxicity with sediment depth, two 20-cm-long replicate cores were collected from a lake historically subjected to the influence of metal mining and smelting activity. The vertical distribution of Pb, Cd and Cu in sediment was similar for all three metals, with the surface layers showing enrichment and the deeper (pre-industrial) layers showing lower concentrations. Toxicity of each sediment core section was determined in laboratory tests with the freshwater amphipod Hyalella azteca. Bioavailable metal in each sediment slice was estimated from metal concentrations in overlying water in these toxicity tests and, for Cd, also from metal bioaccumulation. The profile for Cd in tissue was comparable to Cd in sediment and overlying water, but relative Cd bioavailability from sediment increased with sediment depth. Survival increased with increasing sediment depth, suggesting that surface sediments were probably less or non-toxic before industrialization.

Toxicity of sixty‐three metals and metalloids to Hyalella azteca at two levels of water hardness

The toxicity of all atomically stable metals in the periodic table, excluding Na, Mg, K, and Ca, was measured in one-week exposures using the freshwater amphipod Hyalella azteca in both Lake Ontario, Canada, and soft water (10% Lake Ontario). Metals were added as atomic absorption standards (63 metals), and also as anion salts for 10 metals. Lethal concentrations resulting in 50% mortality (LC50s) were obtained for 48 of the metals tested; the rest were not toxic at 1,000 microg/L. The most toxic metals on a molar basis were Cd, Ag, Pb, Hg, Cr (anion), and Tl, with nominal LC50s ranging from 5 to 58 nmol/L (1 to 58 nmol/L measured). These metals were followed by U, Co, Os, Se (anion), Pt, Lu, Cu, Ce, Zn, Pr, Ni, and Yb with nominal LC50s ranging from 225 to 1,500 nmol/L (88-1,300 nmol/L measured). Most metals were similarly or slightly more toxic in soft water, but Al, Cr, Ge, Pb, and U were >17-fold more toxic in soft water; Pd was less toxic in soft water. Atomic absorption (AA) standards of As and Se in acid had similar toxicity as anions, Sb was more toxic as the AA standard, and Cr and Mn were more toxic as anions. One-week LC50s for H. azteca correlate strongly with three-week LC50s and three-week effect concentrations resulting in 50% reduction in reproduction (EC50s) in Daphnia magna.

A revised classification of the higher taxa of the Ostracoda (Crustacea)

The pilisuctorid ciliate Conidophrys pilisuctor is recorded for the first time as ectosymbiont of the freshwater amphipod Hyalella azteca collected in Patzcuaro Lake, Michoacan, Mexico. The morphometrical data of several phases of its life cycle (except free tomites) and of its prevalence on the host’s body regions are presented. The pilisuctorid was observed attached exclusively to the setae of various appendages from which those of the pereiopods and antennae had the greatest prevalences. However, the results of χ2 tests show that there was not a homogeneous ciliate preference for the body regions of H. azteca. From the cluster analysis, several regions presented a greater degree of similarity according to prevalence and presence--absence of the ciliate. Some aspects are considered for the establishment of symbiosis.