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The median tolerance limits (TLm) of Diquat (1:1-ethylene-2:2′ dipyridylium dibromide) and Dichlobenil (2,6-dichlorobenzonitrile) to one amphipod and larvae of five species of aquatic insects were determined. Diquat was over 300 times more toxic to the amphipod (Hyalella azeteca) than to the mayfly (Callibaetis sp.) while the caddisfly (Limnephilus sp.), tendipedid (Tendipedidae), damselfly (Enallagma sp.), and dragonfly (Libellula sp.) in that order, were more resistant. The addition of pond mud to the test vessels changed the 96-hour TLm of Diquat for the amphipod from 0.046 to 6.8 mg/liter. Dichlobenil was less toxic than Diquat to the amphipod but more toxic to the aquatic insects. Dichlobenil had a narcotizing effect that was recorded as an immobilization concentration (IC50). The addition of pond mud did not reduce the toxicity of Dichlobenil to the caddisfly. The 4% granular formulation of Dichlobenil had a 72-hour “lag” before an effective concentration was obtained equivalent to the toxi...

On August 26 and 27, 1941, collections of young white perch, Morone americana (Gmelin), were made at 8:30 and 11:30 p.m. and at 2:30 and 4:30 a.m. when the fish had moved over shoals. The stomach and intestinal contents of 50 specimens in each collection were examined; estimates were made of the fullness of the stomachs and of the volume of the various food organisms. The position of the food was diagramatically noted. The stomachs examined from the 8:30 p.m. collection held considerable food, but those from subsequent ones held increasingly less, until the 4:30 a.m. collection, when about 95 per cent of the fish examined had empty stomachs. The most important food organisms in the 8:30 p.m. collection were Cladocera, chironomid larvae, and a certain adult of the Hymenoptera. In the following collections, the volume of Cladocera gradually decreased in the digestive tract and such forms as Hyalella, ant adults, midge pupae, and mayfly nymphs increased greatly. In the several collections there was ...

Growth, density, and body size of the deposit-feeding amphipod Hyalella azteca, and its food, epibenthic algae, and sediment microflora, were greatest in shallow-water areas of Marion Lake. The vertical distribution of Hyalella was limited to the upper 2 cm of sediment cores. Highest concentrations of sedimentary chlorophyll and lowest concentrations of nondigestible ligninlike material also occurred at the sediment surface.In laboratory substrate-choice experiments, Hyalella differentiated between sediments with different concentrations of microorganisms, and growth depended upon the quantity of microflora in the diet. In Marion Lake, increased growth of Hyalella during June was independent of temperature and closely correlated with increased rates of epibenthic primary production.Egg production, related to body size in a nonlinear manner, began during May as growth rates increased. As a combined result of egg production and juvenile survival, the maximum density of Hyalella in Marion Lake was reached in August.

Inheritable differences in life history features are shown among three groups of populations of Hyallela azteca from Oregon. Hyallela individuals of coastal populations are relatively small as eggs, as young, and as adults. They grow slowly as young and adults, and the regression of clutch size on female size is relatively steep. Hyallela individuals from the Cascade Mountains are large as eggs, as young, and as adults. They grow rapidly as young and adults, and the regression of clutch size on female size is relatively less steep. A population of Hyalella from a hot springs is made up of animals that are intermediate in these characteristics. The maturation period and the rate of production of egg volume does not differ among the populations investigated. Selection for inconspicuousness, generated by visually orienting predaceous fish, is probably responsible for the small, slow—growing end of the character spectrum (coastal populations). Hyallela is a grazer and deposit feeder, it does not filter. Evidence indicates that larger Hyalella do not have a competitive advantage in predator—free environments, as do larger planktonic filter feeders.

A 19 ha montane reservoir was kept vertically isothermal by aeration all year round. Four macrobenthic species were abundant during the study: Asellus intermedius (isopod), Chaoborus sp. (phantom midge), Hyalella azteca (amphipod), and Lumbriculus inconstans (annelid). Several species of Chironomidae were present and treated collectively. Hyalella significantly increased in abundance in shallow water during destratification. Chironomid larvae declined in abundance in the profundal zone during destratification in Winter and Summer. Asellus, Chaoborus , and Lumbriculus were not significantly altered in abundance during destratification.

LABORATORY STUDIES 380 FIELD STUDIES 381 Population size and structure ...... ......... 381 Reproductive activity 382 Size frequency distribution ....... 383 Individual growth rates ......... 384 Mortality estimations 384 Fish predation 387 DISCUSSION . 388

The density of a deposit-feeding amphipod H&e&z axtecu was varied experimentally in undisturbed sediment cores taken from Marion Lake, British Columbia. Epibenthic algal production, total community respiration, and bacterial oxygen consumption were measured after 4%hr in situ incubation. As density increased community respiration also increased, in a nonlinear manner. Epibenthic algal production was stimulated within the range of natural amphipod densities, but declined at higher densities. Bacterial respiration was stimulated at amphipod densities up to four times those observed in the lake and also declined at higher densities. These data were used to compare microflora production with Hyalella’s daily calorific requirement at various densities. At natural densities, less than 10% of daily microBora production would be required to supply the energy necessary for observed rates of amphipod growth, respiration, and egg production. Fecal pellets produced by HyccE&z were rapidly colonized by microorganisms. Autotrophic microorganisms increased, while respiration of heterotrophic microorganisms and solution decreased organic content of feces. Dissolved organic compounds excreted by Hya2eZla significantly increased the rate of recolonization of fecal material.

The genus Hyalella Smith, 1874 is typical from the continental American waters and show high levels of endemicity. In Brazil, the occurrence of 12 species was reported, of which only Hyalella caeca Pereira 1989 is troglobiotic. A new species was found in a cave, Gruta da Toca, located near Itirapina city, state of São Paulo, Brazil. This species represents the second troglobiotic for the genus in Brazil.

Twenty-four adult and 10 duckling white-winged scoters were collected on four lakes in central Saskatchewan during the summers of 1977–1980. Hyalella azteca was the most important scoter food and made up 97% (aggregate percent dry weight) of the diet for 13 breeding females, 84% for 11 breeding males, and 100% for 10 ducklings. Hyalella azteca was consistently the most abundant food organism present in Eckman dredge samples taken at scoter feeding sites. Adults consumed H. azteca that were significantly larger than those consumed by ducklings. Both adults and ducklings fed primarily by diving at sites 1–3 m deep, but adults fed at deeper sites than ducklings. Timing of reproduction in white-winged scoters seems to be closely timed with increases in the biomass and abundance of Hyalella and possibly other invertebrate foods.

Hyalella armata (Faxon, 1876) was considered for a long time to be a monotypic species. The peculiar morphology, very distinct from other species in Lake Titicaca, was not analysed in detail after the original description. However, the present authors' study of an extensive collection from The Natural History Museum in London has revealed two morphologically distinct species. Descriptions of H. armata and the new species H. longispina are given.Diagnosis of Hyalella longispina n. sp. (Figs 1, 2): Body (Fig. 1) with a posterior dorsal transverse ridge on every segment. Coxae 1 to 4 acuminate. Coxa 4 excavated posteriorly, and with deep acumination at right angle to sagittal body plane. Lateral process of coxa 4 strongly elongate (Fig. 2), distance between left and right process apices longer than body length (that distance shorter than body length in H. armata). Eyes pigmented. Antenna 1 shorter than antenna 2. Antenna 2 less than half body length. Mandible incisor toothed. Maxilla 1 palp uniarticulate, longer than wide, reaching more than half the distance between base of palp and tip of setae on outer plate; inner plate slender, with two strong and pappose apical setae. Maxilla 2 inner plate with one strong pappose seta on inner margin. Gnathopod 1 propodus quadrangular (length less than twice maximum width), hatchet-shaped, inner face with more than ten pappose setae, distoposterior and distoanterior borders without setose scales. Gnathopod 2 propodus triangular, palm longer than posterior margin, slope oblique, anterior edge with a small process. Telson wider than long, apically rounded, with more than two short simple setae, arranged symmetrically on the apical margin. Lateroventral sternal gills present on segments 3 to 7.Types and locality: Holotype male, 10 mm; PERU, Lake Titicaca, Choccocoyo Bay, St. P 6, GIC 481, 11-23 m, leg. Crawford, 25.VI.1937. Paratypes (collecting data as holotype): allotype female, 9 mm; 106 males, 6-10mm; 93 females, 5-10 mm. All deposited at The Natural History Museum, London (holotype: 2002.311; allotype: 2002.312; other paratypes: 2002.313-322).

A new standardized bioassay procedure for testing the chronic toxicity of sediments to Hyalella azteca was developed. Tests were initiated with 0–1 wk old amphipods exposed to sediments from Hamilton Harbour, Toronto Harbour, and Lake Ontario for 4 to 8 weeks. Both survival and growth were significantly reduced in the Hamilton Harbour sediments relative to those from the lake after 4 weeks. Exposures of 8 weeks resulted in greater variability; survival of amphipods in sediments from one of the harbour stations, and growth in sediments from both harbour stations with surviving young were not statistically different from survival and growth in lake sediments. Growth and survival in lake sediments were comparable to cultures grown with cotton gauze and no sediment after 4 weeks, but survival was poorer by week 8. Replication was good in 12 out of 13 tests done in duplicate; the difference in survival between replicates averaged 2.2 animals (20 amphipods/replicate, 4 week exposure). We propose that 4 week exposures of young (0–1 wk old) Hyalella would provide a suitable standardized chronic toxicity test for sediments. A detailed protocol on the methodology is presented.

Submitted by Alberto Vieira (martins_vieira@ibest.com.br) on 2017-09-19T17:30:27Z No. of bitstreams: 1 200939.pdf: 5887897 bytes, checksum: 6bc012a89a34a6aaba00a67e985d0879 (MD5) Made available in DSpace on 2017-09-19T17:30:27Z (GMT). No. of bitstreams: 1 200939.pdf: 5887897 bytes, checksum: 6bc012a89a34a6aaba00a67e985d0879 (MD5) Previous issue date: 1983 Estudo sistemático das espécies de Hyalella Smith, 1874 (Crustacea-Amphipoda) com base em material obtido em diferentes localidades do território brasileiro, e que se acha depositado na coleção carcinológica do Museu Nacional do Rio de Janeiro. Foram encontradas 6 espécies, das quais 4 (Hyalella azteca, H. pernix, H. warmingi, H. meinerti) já haviam sido citadas para o Brasil e duas (H serrana, H. caeca) são consideradas novas para a ciência. Todas, como é peculiar no gênero, habitam água doce sendo que H. caeca é tipicamente troglóbia, H. warmingi é troglofila e as demais são epígeas. H. longistila (Faxon) também descrita para o Brasil, não foi encontrada no material estudado, razão pela qual não é aqui tratada. Além de uma chave de classificação para as espécies conhecidas do Brasil, é apresentada uma descrição detalhada de cada uma das 6 espécies estudadas, acompanhada de figuras, discussão, indicação da distribuição geográfica e localidade - tipo, quando for o caso. Consta também do trabalho, uma lista de todas as espécies conhecidas de Hyalella no mundo, com indicação em um mapa, da distribuição geográfica de cada. A distribuição das 6 espécies brasileiras aqui tratadas, de acordo com as localidades em que os espécimes foram coletados, é também mostrada num mapa à parte. A systematic is made of the species of Hyalella Smith (Crustacea-Amphipoda) based on material gathered at different points of the Brazilian territory, which is kept at the carcinological collection of the Museu Nacional, Rio de Janeiro. Six species were found, four of which (Hyalella azteca, H. pernix, H. warmingi, H. meinerti) have been previously recorded for Brazil and were considered new to science (H serrana, H. caeca). All are, as peculiar to the genus, fresh water dwellers, H. caeca being typically troglobitic, H. warmingi occasionally so, and the remaining ones epigean. H. longistila (Faxon) also record from Brazil, has not been found in the material studied, and therefore is not here dealed with. Besides a Key for species known to occur in Brazil, detailed descriptions and illustrations are given for each of the six species studied and also their geographical distribution and type-locality. A list is also included of the species of Hyaella of the world with record on a map of their geographical distribution. The distribution of the six brazilian species here studied, showing the localities where the specimens were collected, is also present on a separate map.

Salinity of Pyramid Lake increased from 3.7 to 5.5‰ between 1933 and 1980. Concern over future reductions in overall species richness prompted experiments to assess responses of dominant lake organisms to elevated salinity. Salinity tolerances of three important benthic invertebrates, Hyalella aztecta, Chironomus utahensis, and Heterocypris sp., were tested in controlled laboratory bioassays and also in a semi-natural environment consisting of large (47 m3) mesocosms.

The ecosystem health of stressed environments in the Great Lakes has been evaluated simultaneously by means of a battery of structural and functional tests based on current technology and involving various trophic levels. These tests attempt to assess ecosystem health at the organism level and simultaneously focus on water-borne and sediment-bound toxicities. The use of structural indicators has been successfully demonstrated. Similarly, functional tests were selectively chosen across various trophic levels and included size-fractionated primary productivity (filtered versus unfiltered assays), and Colpidium, Daphnia, Hyalella, and Pontoporeia assays. Some of the emerging techniques such as in situ plankton cages (I.P.C.), microcomputer-based chlorophyll fluorescence (Video Analysis System), and other assays are discussed. The multi-trophic and multi-disciplinary battery of tests followed in our laboratory adopts a field-to-laboratory approach. The availability of diverse bioassays have placed toxicologists and environmentalists in a position where they are now better equipped to probe the complexities of ecosystem health and its management.

The relationship between bioaccumulation and toxicity of tributyltin in Hyalella azteca was determined for future use in identifying freshwater sites of TBT induced toxicity in the field. Hyalella accumulated waterborne TBT rapidly, reaching equilibrium within 1 week. Short exposure times are, therefore, sufficient to measure TBT availability in laboratory or field exposures. Accumulation was not affected significantly by body size for animals between 0.1 and 0.6 mg dry weight, eliminating the need for a body size correction factor. Young amphipods were more sensitive to TBT than adults when both were exposed for 1 week. The 4-wk LC50 initiated with 0–1-week-old young was 4.8 nM. TBT accumulation was approximately proportional to TBT in water, and the 4-week LC50 expressed on a body concentration basis was 110 nmole/g dry weight. Accumulation of TBT by adult Hyalella to concentrations of about 100 nmole/g or more during short term (1-wk) exposures to environmental samples would suggest chronic TBT-induced toxicity is present at those sites.

Increasing amounts of engineered nanoparticles (NPs) in wastewater can reach the aquatic environment by passing through the sewage treatment plant (STP). NPs can induce ecotoxicological effects due to their specific chemical properties. However, their bioavailability and toxicity are potentially influenced by transformation processes caused by substances present in the STP, e.g., humic acids or sulfides. Due to the lack of a test system allowing to test NPs under realistic environmental conditions, we coupled two existing test systems, the activated sludge simulation test (OECD TG 303A 2001) and the chronic exposure test with the freshwater amphipod Hyalella azteca (Environment Canada 2013), to gain a test scenario that allows to consider the altered behavior and fate of NPs induced by the STP process. This should improve the environmental realism of the chronic exposure test with Hyalella. In the first study, we tested the STP effluent containing AgNPs. In the second and third study, tap water and control STP effluent were spiked with AgNPs and used as test media. The chronic exposure studies with the freshwater amphipod H. azteca showed that the investigated AgNPs lose most of their toxicity while passing through the STP. Over all studies with total Ag concentrations ranging from 0.85 to 68.70 µg/L, significant effects of the AgNPs were only observed in the survival of test animals exposed to tap water containing the highest Ag concentration (62.59 µg/L). Accumulation of silver in the body of test animals was clearly dependent on the pretreatment of the AgNPs. Silver ions (Ag+) released from AgNPs are supposed to be the major pathway leading to body burden following exposure to test media containing AgNPs. The coupled test system is suitable for testing substances that can reach the environment via the STP effluent. The investigated AgNPs lose most of their toxicity while passing through the STP. Accumulation of silver in the animals exposed to the different treatments was apparent, whereby silver ions (Ag+) released from AgNPs were supposed to be the major pathway leading to body burden.

The population dynamics of the crayfish, Orconectes virilis, were studied to define the role of the crayfish as a consumer in a marl lake ecosystem. Insight was gained into the factors controlling its production. There was year-class fluctuation in the age structure of the crayfish population. Males had a greater growth rate than females. After age-I, mortality rates for females were greater than for males. Both sexes matured after a molt in July, at age-I; mating followed and eggs were laid the following spring. Reproductive capacity was 58% of the potential capacity. Two-year-old females produced most of the eggs (92.5%). The estimated reproductive rate for 1963 was low (0.78 per generation) due to poor survival of the 1963 year class. The maximum life span for both sexes was three years. Newly hatched young left the females and remained in shallow water. Adult females then molted and migrated to a depth of 7.6 m, where most of them remained all summer. A migration of males to deep water followed. 0. virilis acts as a herbivore in marl lakes, feeding chiefly on the algae and the "aufwuchs" with marl incrustations, though it is also a scavenger on animal materials. The peak standing crop of crayfish (119.5 kg/ha) occurred in the spring of 1963. The annual net production of crayfish was 205.3 kg/ha, about 8.9 times greater than an estimate of the productio-n of all other bottom invertebrates in West Lost Lake (23.0 kg/ha). The total net production of 310.8 kg was 2.33 times the average standing crop during the summer of 1963. This crayfish has a lower daily numerical turnover rate (2.0%) than the amphipod Hyalella (2.9%) and the cladoceran Daphnia (25.0%). Population size is probably regulated by cannibalism and natural mortality at molting.