Freshwater Amphipod Hyalella Azteca Research Articles

Time‐dependent toxicity of dichlorodiphenyldichloroethylene to Hyalella azteca

Temporal effects on body residues of dichlorodiphenyldichloroethylene (DDE) associated with mortality in the freshwater amphipod Hyalella azteca were evaluated. Toxicokinetics and body residues were determined from water-only exposures that varied from 4 to 28 d, and DDE concentrations ranging from 0.0013 to 0.045 micromol L(-1). Uptake and elimination parameters were not affected significantly by the various temporal and concentration treatments. Uptake rate coefficients ranged from 134.3 to 586.7 ml g(-1) h(-1), and elimination rate coefficients ranged from 0.0011 to 0.0249 h(-1). Toxicity metric values included body residue for 50% mortality at a fixed sample time (LR50) and mean lethal residue to produce 50% mortality from individual exposure concentrations (MLR50) for live organisms and dead organisms. A twofold increase occurred in the MLR50 values calculated using live organisms compared to MLR50 values using dead organisms. Toxicity and kinetic data were fit to a damage assessment model that allows for the time course for toxicokinetics and damage repair, demonstrating the time-dependence of body residues to toxicity. The DDE appeared to act through a nonpolar narcosis mode of action for both acute and chronic mortality in H. azteca. Furthermore, the temporal trend in the toxic response using body residue as the dose metric is steep and found to be similar to another chlorinated hydrocarbon, pentachlorobenzene, but was more potent than that found for polycyclic aromatic hydrocarbons (PAHs).

Testing sediment biological effects with the freshwater amphipod Hyalella azteca: the gap between laboratory and nature

The freshwater amphipod, Hyalella azteca, is widely used in laboratory sediment toxicity and bioaccumulation tests. However, its responses in the laboratory are probably very different from those in the field. A review of the literature indicates that in its natural habitat this species complex is primarily epibenthic, derives little nutrition from the sediments, and responds primarily to contaminants in the overlying water column (including water and food), not sediment or porewater. In laboratory sediment toxicity tests H. azteca is deprived of natural food sources such as algal communities on or above the sediments, and is subjected to constant light without any cover except that afforded by burial into the sediments. Under these constraining laboratory conditions, H. azteca has been reported to respond to sediment or porewater contamination. In nature, contamination of overlying water from sediment is less likely than in the laboratory because of the large, generally non-static sink of natural surface water. H. azteca does not appear to be the most appropriate test species for direct assessments of the bioavailability and toxicity of sediment contaminants, though it is probably appropriate for testing the toxicity of surface waters. Toxic and non-toxic responses will be highly conservative, though the latter are probably the most persuasive given the exposure constraints. Thus H. azteca is probably a suitable surrogate species for determining sediments that are likely not toxic to field populations; however, it is not suitable for determining sediments that are likely toxic to field populations.

Effects of 17α-ethinylestradiol on sexual development of the amphipod Hyalella azteca

The effects of the synthetic estrogen 17 α-ethinylestradiol (EE) on sexual development of the freshwater amphipod Hyalella azteca was investigated. Organisms were exposed in a multigeneration experiment to EE concentrations ranging from 0.1 to 10 μg/L and the development of both external and internal sexual characteristics were studied. Second-generation male H. azteca exposed from gametogenesis until adulthood to 0.1 and 0.32 μg EE/L developed significantly smaller second gnathopods. The sex ratio of the populations exposed to EE for more than two generations tended, although not statistically significantly, to be in favor of females. Histological aberrations of the reproductive tract, i.e., indications of hermaphroditism, disturbed maturation of the germ cells, and disturbed spermatogenesis, of post-F1-generation males were observed in all EE exposures. These findings provide evidence that sexual development of H. azteca is affected by exposure to sublethal concentrations of EE.

Effects of chronic copper exposure on the nutritional composition of Hyalella azteca

The toxicity of dietborne metals currently is a topic of high interest in aquatic toxicology. We hypothesized that, in addition to causing direct physiological effects when ingested by organisms, dietborne metals might also cause indirect foodweb effects. One such indirect effect might be alteration of the nutritional content of prey, leading to decreased growth and (or) survival of consumers. Because dietborne and waterborne metal exposures usually occur concurrently in aquatic ecosystems, we exposed two generations of a representative grazer species—the freshwater amphipod Hyalella azteca—to dietborne copper (Cu) concurrent with waterborne Cu in the laboratory for a total of 27 days (first generation) and 45–57 days (second generation). The aqueous Cu concentrations were 0.0099 (control), 0.054 and 0.11 μM (0.6, 3.4 and 7.0 μg Cu per l, respectively) at 24 °C, pH 7.5–8.3, alkalinity of ∼3 mEq/l and hardness of ∼4 mEq/l; whereas the dietborne Cu exposures were via biofilm growing on cotton gauze in the same exposure aquaria. In a preliminary test, we demonstrated that the highest Cu concentrations were at the threshold for adversely affecting survival and reproduction. In the two-generation test, first- and second-generation amphipods exposed to the intermediate and high aqueous Cu concentrations accumulated significantly higher amounts of Cu than control amphipods. However, none of the traditional nutritional composition categories (protein, total lipid, ash and ‘other’) differed among the treatments. The only significant difference in nutritional composition was an elevated concentration of linolenic acid (18:3 n−3) in the second-generation amphipods exposed to 0.054 μM Cu.

Effects of contaminants in dredge material from the lower Savannah River.

Contaminants entering aquatic systems from agricultural, industrial, and municipal activities are generally sequestered in bottom sediments. The environmental significance of contaminants associated with sediments dredged from Savannah Harbor, Georgia, USA, are unknown. To evaluate potential effects of contaminants in river sediments and sediments dredged and stored in upland disposal areas on fish and wildlife species, solid-phase sediment and sediment pore water from Front River, Back River, an unnamed Tidal Creek on Back River, and Middle River of the distributary system of the lower Savannah River were tested for toxicity using the freshwater amphipod Hyalella azteca. In addition, bioaccumulation of metals from sediments collected from two dredge-disposal areas was determined using the freshwater oligochaete Lumbriculus variegatus. Livers from green-winged teals (Anas crecca) and lesser yellowlegs (Tringa flavipes) foraging in the dredge-spoil areas and raccoons (Procyon lotor) from the dredge-disposal/river area and an upland site were collected for metal analyses. Survival of H. azteca was not reduced in solid-phase sediment exposures, but was reduced in pore water from several locations receiving drainage from dredge-disposal areas. Basic water chemistry (ammonia, alkalinity, salinity) was responsible for the reduced survival at several sites, but PAHs, metals, and other unidentified factors were responsible at other sites. Metal residues in sediments from the Tidal Creek and Middle River reflected drainage or seepage from adjacent dredge-disposal areas, which could potentially reduce habitat quality in these areas. Trace metals increased in L. variegatus exposed in the laboratory to dredge-disposal sediments; As, Cu, Hg, Se, and Zn bioaccumulated to concentrations higher than those in the sediments. Certain metals (Cd, Hg, Mo, Se) were higher in livers of birds and raccoons than those in dredge-spoil sediments suggesting bioavailability. Cadmium, Cr, Hg, Pb, and Se in livers from raccoons collected near the river and dredge-disposal areas were significantly higher than those of raccoons from the upland control site. Evidence of bioaccumulation from laboratory and field evaluations and concentrations in sediments from dredge-disposal areas and river channels demonstrated that some metals in the dredge-disposal areas are mobile and biologically available. Drainage from dredge-disposal areas may be impacting habitat quality in the river, and fish and wildlife that feed and nest in the disposal areas on the lower Savannah River may be at risk from metal contamination.

Photo-induced toxicity of PAHs to Hyalella azteca and Chironomus tentans: effects of mixtures and behavior

In the aquatic environment, polycyclic aromatic hydrocarbon (PAH) contamination can result from several anthropogenic sources such as petroleum runoff, industrial processes, and petroleum spills. When ultraviolet light (UV) is present at sufficient intensity, the acute toxicity of some PAHs to aquatic biota is greatly enhanced. This photo-induced toxicity of PAHs is directly influenced by the amount of PAH and by the level of UV intensity present in the aquatic environment. Thus, behavioral responses and habits that affect an aquatic organism's exposure to UV as well as exposure to PAHs can influence the extent to which damage due to photo-induced toxicity occurs. Experiments demonstrated the effects of photo-induced toxicity of anthracene and fluoranthene on the survival of two benthic macroinvertebrates, the midge Chironomus tentans and the freshwater amphipod Hyalella azteca. This study further investigated the survival and behavior of the test organisms in different substrates (no substrate, a sand monolayer, leaf discs, and sediment) with and without UV. The free-swimming, epibenthic H. azteca avoided the effects of photo-induced toxicity of PAHs to some extent by hiding in leaves when this substrate was available. Results emphasize the importance of organisms' behavior in affecting the photo-induced toxicity of PAHs in the aquatic environment.

Sediment toxicity evaluation for hexachlorobenzene: spiked sediment tests with Leptocheirus plumulosus, Hyalella azteca, and Chironomus tentans.

Hexachlorobenzene (HCB) is a hydrophobic organic chemical that has shown a lack of toxicity in aquatic tests at concentrations up to and exceeding the solubility limit. The equilibrium partitioning approach to deriving sediment quality benchmarks, which assumes that toxicity can be predicted based on contaminant concentrations in interstitial water, predicts that HCB will not produce direct toxicity to benthic invertebrates as a sediment contaminant. However, the potential for toxicity due to direct exposure to sediment-adsorbed HCB has not been thoroughly established. This study evaluated the survival and growth of the estuarine amphipod Leptocheirus plumulosus, the freshwater amphipod Hyalella azteca, and the midge Chironomus tentans (freshwater) following 10-day exposure to sediment spiked with a range of HCB concentrations. H. azteca was tested under both freshwater and estuarine (10 ppt salinity) conditions. No significant toxicity was observed for any test species at the highest test concentration (60 mg/kg normalized to 1% organic carbon). Minimum detectable differences were less than or equal to 20% for three of eight test endpoints. The observed results add to the available weight of evidence indicating a limited potential for HCB-related sediment toxicity to benthic invertebrates.

Genetic variation and reproductive isolation among phenotypically divergent amphipod populations

We examined the degree of reproductive isolation and patterns of genetic structure and diversification within and among seven populations of the freshwater amphipod Hyalella azteca. Hyalella occurs across ecologically dissimilar habitats in southeastern Michigan and exhibits substantial, and apparently adaptive, genetically based phenotypic variation among populations. Habitats with predatory centrarchid fish contain a small‐bodied Hyalella ecotype, whereas habitats lacking these predators contain a large‐bodied ecotype. Hierarchical F statistics showed that allele frequency variation at six electrophoretic loci is greater among populations within an ecotype than between ecotypes, a result also reflected in a cluster analysis based on genetic distances among the seven populations. Despite the lack of clear genetic differentiation between ecotypes, gene flow between ecotypes appeared restricted or absent. Physically adjacent large‐ and small‐ecotype populations in the same drainage differed appreciably in allele frequencies. Within‐population genetic structuring also differed between ecotypes. Whereas genotype frequencies never differed from Hardy‐Weinberg expectations in large‐ecotype populations, all small‐ecotype populations exhibited a significant deficiency of heterozygous genotypes at one or more loci. Interbreeding trials demonstrated that individuals from different populations of the same ecotype readily interbreed, but no interbreeding was observed in crosses involving individuals of dissimilar ecotypes. Interbreeding results, considered together with between‐ecotype differences in allele and genotype structure, suggest that Hyalella ecotypes in southeast Michigan form at least two separate species. Furthermore, the lack of distinct allelic differences and the relative levels of allele frequency differentiation within and between ecotypes suggest recent local speciation in this taxon.

Effects of temperature on individual growth rate and body size of a freshwater amphipod

Individual growth rates of the freshwater amphipod Hyalella azteca (Saussure) were measured in the littoral zone oftwo small oligotrophic Ontario lakes and in growth experiments over a natural temperature gradient (10, 15, 20, and 238C).Field observations showed that a temperature of 208C is important for both the induction and termination of reproductiveresting stages in H. azteca. Growth rates were more affected by temperature in small than in large individuals. Growthparameters are related to rearing temperature by linear regressions, which can be used as a simple model for bioenergeticscalculations in crustaceans. A negative relationship between water temperature and maximum size attained by the amphipodswas found. The largest adults were absent in studied populations when summer temperatures were high, and this phenomenon,which has also been observed in other aquatic invertebrates, was bioenergetically determined. Energy-budget estimationsshowed negative net growth efficiency (K2) in the largest adults at temperatures above 208C. The relationship between K2andtemperature showed a dome-shaped pattern, K2values for larger amphipods being maximal at lower temperatures. Seasonalmigrations of adult H. azteca from shallow littoral to deeper cold habitats, observed in lakes during the warmest periods, appearto be temperature-induced and bioenergetically advantageous, despite probable increases in predation risk experienced inspatially simple deep-water habitats.

Effects of temperature on individual growth rate and body size of a freshwater amphipod

Individual growth rates of the freshwater amphipod Hyalella azteca (Saussure) were measured in the littoral zone oftwo small oligotrophic Ontario lakes and in growth experiments over a natural temperature gradient (10, 15, 20, and 238C).Field observations showed that a temperature of 208C is important for both the induction and termination of reproductiveresting stages in H. azteca. Growth rates were more affected by temperature in small than in large individuals. Growthparameters are related to rearing temperature by linear regressions, which can be used as a simple model for bioenergeticscalculations in crustaceans. A negative relationship between water temperature and maximum size attained by the amphipodswas found. The largest adults were absent in studied populations when summer temperatures were high, and this phenomenon,which has also been observed in other aquatic invertebrates, was bioenergetically determined. Energy-budget estimationsshowed negative net growth efficiency (K 2) in the largest adults at temperatures above 208C. The relationship between K 2 andtemperature showed a dome-shaped pattern, K 2 values for larger amphipods being maximal at lower temperatures. Seasonalmigrations of adult H. azteca from shallow littoral to deeper cold habitats, observed in lakes during the warmest periods, appearto be temperature-induced and bioenergetically advantageous, despite probable increases in predation risk experienced inspatially simple deep-water habitats.

Effect of acute pH depression on the survival of the freshwater amphipod Hyalella azteca at variable temperatures: field and laboratory studies

Field observations on temperature and pH of a small pond showed that a amphipod population of Hyalella azteca was exposed to variable seasonal pH between 5.10–5.85, and water temperatures between 2–21 °C. Laboratory experiments were designed to simulate seasonal temperatures and field pHs of a small pond habitat. Laboratory bioassay experiments were conducted to determine the survival of Hyalella azteca at pHs 4, 5, 6 and 7, and varying temperatures of 5°, 10°, 15°, 20° and 25 °C.

Sexual Dimorphism and Mate Choice in Hyalella azteca (Amphipoda)

-The mating system of the freshwater amphipod Hyalella azteca consists of precopulatory mate guarding, in which males compete for the possession of females by guarding them before copulation. Although males in the field population are on average significantly heavier than females, males in precopula are not proportionately heavier than the females they carry, indicating that precopulatory mate guarding takes place in a nonsize assortative manner. In the laboratory, the guarding pattern and pairing success are dependent upon the operational sex ratio (OSR). When the OSR is female-biased, males are more successful at obtaining females due to the active male mate choice, but when OSR is malebiased, females are less frequently taken into precopula because of intensified male-male interference. At female/male OSR values of 1:2 or 2:1, males demonstrate a preference for large prospective mates. However, at the OSR values of 1:3 or 3:1, pairs are randomly formed with no size-dependent responses. This flexibility of guarding behavior is explained by time and energy investment tactics in mate selection by both sexes.

Responses of the Freshwater AmphipodHyalella aztecato Environmental Acidification

Effects of acidification on the freshwater amphipod Hyalella azteca were investigated by examining the role of pH on natural distribution of the species in 30 northwestern Ontario lakes and by determining its responses to acidification in a series of field and laboratory experiments. The amphipod was absent from all five lakes that had pH 5.03–5.40 or Ca concentration < 1.24 mg/L and was present in 23 of the 25 remaining lakes that had pH > 6.0 and Ca > 1.24 mg/L. In the field and laboratory experiments, amphipods transplanted to acidified lakes (pH 5.45, 5.66) or held in 500-L bags [Formula: see text] or 4-L aquaria [Formula: see text] showed lower survival than those held in corresponding neutral-pH, control treatments (P < 0.05). Neonate H. azteca were less tolerant of low pH than those in later life-history stages (P < 0.05). Populations of H. azteca will decline in habitats where the pH remains < 5.8, a condition extant in a substantial proportion of lakes in eastern North America.

Effect of sediment organic carbon on survival of hyalella azteca exposed to DDT and endrin

AbstractSediment toxicity tests were conducted with the freshwater amphipod Hyalella azteca using sediments ranging in total organic carbon (TOC) concentration from 3 to 11 % and spiked with either DDT or endrin. While the toxicity in the DDT‐spiked sediment decreased with increasing TOC content, the TOC content of the endrin‐spiked sediment had little apparent effect on toxicity. The 10‐d sediment dry‐weight LC50 for DDT was 11.0 μg/g at 3.0% TOC and 49.7 μg/g at 10.5% TOC. The sediment dry weight LC50s for endrin at 3.0 and 11.2% TOC were 4.4 and 6.0 μg/L, respectively. These results are important in evaluating the carbon normalization theory, which assumes that the availability of nonpolar organic compounds is reduced in the presence of higher concentrations of TOC. The differences in adsorption and toxicity between DDT and endrin are presumably related to the smaller carbon (Koc) and octanol/water (Kow) partition coefficients of endrin.

Lake Acidification as a Limiting Factor in the Distribution of the Freshwater Amphipod Hyalella azteca

The distribution of the freshwater amphipod Hyalella azteca in 79 Ontario lakes suggests that its absence may be a good indicator of lake acidification. Hyalella azteca was present in 69 of 71 nonacidified lakes, and absent in 8 of 8 lakes which either are now ar recently were considered acidified. Bioassay data indicate a 96-h LC50 of pH 4.4 and a 10-d threshold LC50 of pH 4.5 for H. azteca in a natural surface water. Hyalella azteca is extremely rare in Plastic Lake, which undergoes severe short-term acidification in spring, and recruitment is delayed 2 wk in Heeney Lake which undergoes similar short-term acidification, in Dickie, Harp, Red Chalk, and Blue Chalk lakes, where springtime pH depressions below pH 4.7 were not recorded, H. azteca is abundant.

Digestive anatomy of Halella azteca (Crustacea, Amphipoda).

The digestive tract of the freshwater amphipod Hyalella azteca is a straight but differentiated tube consisting of foregut, midgut, and hindgut divisions. The foregut is subdivided into a tubular esophagus, a cardiac stomach, and a pyloric stomach. The cuticular lining of the cardiac stomach is elaborated into a set of food-crushing plates and ossicles, the gastric mill, while the pyloric cuticle forms a complex straining and pressing mechanism. Nine caeca arise from the midgut, seven anteriorly and two posteriorly. Four of the anterior caeca, the hepatopancreatic caeca, are believed to be the primary sites of digestion and absorption. The remaining caeca may be absorptive, secretory, or both. The much-folded hindgut wall is capable of great distention by extrinsic muscle action for water intake to aid in flushing fecal material out of the anus; such action also may stimulate antiperistalsis by intrinsic rectal muscles.

The Effects of Population Density upon Growth Reproduction, and Survival of Hyalella azteca

T -HE problems of the biotic relationships of like organisms have attracted much interest. Naturalists have reported with enthusiasm noteworthy aggregations, sexual behavior, and social manifestations. This work continues but with a more critical attitude. The less obvious mass relations, seen only by resultant effects, led to a dichotomy of interest, which in the future and to some extent at present (Park, 1939) will coalesce. One approach is that of the study of the whole population, its growth, maintenance, and decline or evolution (Chapman, 1928; Wright, 1931; Gause, 1934; Bodenheimer, 1938). The other is the study of physiological or behavioristic effects of population density upon the constituent organisms (Allee, 1931, 1934, 1938). The physiological aspect is considered in the present study,' which attempts a demonstration of the effects of increasing the density of the population upon three fundamental processes: growth, reproduction, and survival. As an assay animal the common freshwater amphipod Hyalella azteca Saussure2 (H. knickerbockeri Bate), Orchestiidae, was chosen. In the use of an aquatic arthropod the study is unique among researches comparable in nature to those of Pearl and of others to be cited later. The conditions of the experiments were variable, but equal volumes of food and water were used in all, irrespective of numbers of animals present. The following brief review of the literature is necessarily closely confined to the question studied and deals with recent studies on arthropods. The references given in the first paragraph include summaries of results on population studies of other forms. Earlier work by the same or different authors may be found by consultation of the literature referred to below. Growth.-Body size (Warren, 1900oo) and rate of development (Banta, 1937) were retarded in Cladocera by crowding or its concomitant factors. Metamorphosis in the beetle Tribolium confusum was delayed, and body weight was reduced (Park, 1938) in relation to the density of the population and more directly to the degree of conditioning of the medium. On the other hand, evidence is present for an augmentative effect of increasing numbers of organisms. Development is accelerated in Periplaneta orientalis after the ninth instar, and the effect is apparent even in a density as low as 2 animals. However, the longest and heaviest animals were found among the isolated individuals, an effect attributed to increased disturbance by collision in higher densities (Landowski, 1938). Meal worms (Tenebrio molitor) raised 50 together in 60 cc. of meal consistently weighed more than did isolated larvae; even 150 animals in a similar volume maintained a higher weight than that of isolated ones until the sixtieth day (Michal, 1931). This was