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Fishes have spread into previously fishless wetlands, likely affecting other species. In the Prairie Pothole Region of North America, the invasion of fish into wetlands is facilitated by interactions of altered land use, climate, and hydrology. We aimed to understand the effects of fishes on amphipods, which are macroinvertebrates that vertebrates rely on as forage. We hypothesized the presence and abundance of fish, particularly benthivores, would have detrimental effects on amphipod abundance. Our study design targeted a large gradient of amphipod abundances among wetlands, including very high abundances of two amphipod species: Gammarus lacustris and Hyalella azteca. We found that fishless basins had twice as many amphipods as those with fish, on average. Gammarus lacustris were not detected in the presence of Black Bullhead Ameiurus melas. The abundance of both amphipod species had negative associations with the most common fishes, Fathead Minnow Pimephales promelas and Brook Stickleback Culaea inconstans. A multivariate community analysis showed the benthivore-fish functional feeding guild was negatively associated with the amphipod community, as hypothesized. However, our study design captured several wetlands with anomalies of high abundances of both fish and amphipods, obscuring their relationships. Our results aid resource managers by confirming several fish guilds and species are associated with lower abundances of amphipods. These findings can inform resource managers who make decisions about managing for fish and wildlife; for example, they may choose to manage existing fish populations or protect existing wetlands with high amphipod densities from new fish invasions. [ABSTRACT FROM AUTHOR]

In the present study, the acute toxic effects of single, double, and triple mixtures of imidacloprid, azoxystrobin, and glyphosate on Gammarus lacustris were investigated. Initially, the 96-hour median lethal dose (LC50) values for imidacloprid, azoxystrobin, and glyphosate were determined as 157, 1.92, and 4.33 mg L−1, respectively. The animals were exposed to one-fiftieth of the 96-h LC50 concentration for 24 or 96 h. The activity of glutathione S-transferase (GST), glutathione reductase, acetylcholinesterase, carboxylesterase (CaE), and superoxide dismutase enzymes as biological markers were examined to determine the non-lethal effects of the pesticides tested. Significant changes were observed in GST and CaE activities especially in detoxification compared to control and between different applications. The results of this study show the potential for increased toxicity in organisms exposed to pesticide mixtures. [ABSTRACT FROM AUTHOR]

Species of littoral freshwater environments in regions with continental climate experience pronounced seasonal temperature changes. Coping with long cold winters and hot summers requires specific physiological and behavioural adaptations. Endemic amphipods of Lake Baikal, Eulimnogammarus verrucosus and Eulimnogammarus cyaneus, show high metabolic activity throughout the year; E. verrucosus even reproduces in winter. In contrast, the widespread Holarctic amphipod Gammarus lacustris overwinters in torpor. This study investigated the transcriptomic hallmarks of E. verrucosus, E. cyaneus and G. lacustris exposed to low water temperatures. Amphipods were exposed to 1.5°C and 12°C (corresponding to the mean winter and summer water temperatures, respectively, in the Baikal littoral) for one month. At 1.5°C, G. lacustris showed upregulation of ribosome biogenesis and mRNA processing genes, as well as downregulation of genes related to growth, reproduction and locomotor activity, indicating enhanced energy allocation to somatic maintenance. Our results suggest that the mitogen‑activated protein kinase (MAPK) signalling pathway is involved in the preparation for hibernation; downregulation of the actin cytoskeleton pathway genes could relate to the observed low locomotor activity of G. lacustris at 1.5°C. The differences between the transcriptomes of E. verrucosus and E. cyaneus from the 1.5°C and 12°C exposures were considerably smaller than for G. lacustris. In E. verrucosus, cold‐exposure triggered reproductive activity was indicated by upregulation of respective genes, whereas in E. cyaneus, genes related to mitochondria functioning were upregulated, indicating cold compensation in this species. Our data elucidate the molecular characteristics behind the different adaptations of amphipod species from the Lake Baikal area to winter conditions. [ABSTRACT FROM AUTHOR]

Species with effective thermal adaptation mechanisms allowing them to thrive within a wide temperature range can benefit from climatic changes as they can displace highly specialized species. Here, we studied the adaptive capabilities of the Baikal endemic amphipods Eulimnogammarus verrucosus (Gerstfeld, 1858) and Eulimnogammarus cyaneus (Dybowsky, 1874) compared to the potential Holarctic Baikal invader Gammarus lacustris Sars, 1863 at the cellular level including the energy metabolism and the antioxidant system. All species were long-term exposed to a range of temperatures (1.5 °C to mimic winter conditions and the three species-specific preferred temperatures (i.e., 6 °C for E. verrucosus, 12 °C for E. cyaneus and 15 °C for G. lacustris). At 1.5 °C, we found species-specific metabolic alterations (i.e., significantly reduced ATP content and lactate dehydrogenase activity) indicating limitations on the activity level in the Holarctic G. lacustris. Although the two Baikal endemic amphipod species largely differ in thermal tolerance, no such limitations were found at 1.5 °C. However, the cold-stenothermal Baikal endemic E. verrucosus showed changes indicating a higher involvement of anaerobic metabolism at 12 °C and 15 °C, while the metabolic responses of the more eurythermal Baikal endemic E. cyaneus may support aerobic metabolism and an active lifestyle at all exposure temperatures. Rising temperatures in summer may provide a competitive advantage for G. lacustris compared to the Baikal species but the inactive lifestyle in the cold is likely preventing G. lacustris from establishing a stable population in Lake Baikal. [ABSTRACT FROM AUTHOR]

Gammarus lacustris is native to the Qinghai–Tibet Plateau (QTP), widely distributed in alpine lakes. The complete mitochondrial DNA sequence of G. lacustris was 15,349 base pairs in length and comprised 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 control region. The BI tree showed that G. lacustris was most closely related to Gammarus duebeni, and indicated that Gammarus, Gmelinoides, Brachyuropus, Pallaseopsis, and Eulimnogammarus evolved from a common ancestor. The mitogenome of G. lacustris provides new molecular data for further taxonomic and phylogenetic studies of Amphipoda.

The aim of the present study was to estimate the cohabitation effect of two invasive amphipods species (Gammarus lacustris and Gmelinoides fasciatus) by the cellular stress markers such as activity of antioxidant enzymes (peroxidase, catalase, glutathione S-transferase) and content of heat shock protein 70 (HSP70). Changes of antioxidant enzymes activity were shown in both amphipods species. It was observed that in G. lacustris cohabitation with other species led to the activation of all studied enzymes, whereas in G. fasciatus only peroxidase activity alteration was recorded. Notably, the activation of all studied enzymes was short-term. There were no changes of HSP70 content for both species. According to obtained data less sensitivity of G. fasciatus stress markers can be one of the key advantages for further successful distribution and adaptation to the new conditions.

Direct consumption on free-living cercariae stages of trematodes by non-host organisms interferes with trematode transmission and leads to reduced infections in the next suitable hosts. Consumer functional responses provide a useful tool to examine relationships between consumption rates and ecologically relevant prey densities, whilst also accounting for abiotic factors that likely influence consumption rates. We investigated how temperature influences the consumer functional response of the amphipod Gammarus lacustris towards the cercariae of three freshwater trematodes (Diplostomum, Apatemon and Trichobilharzia). Amphipods displayed different functional responses towards the parasites, with Type II responses for Diplostomum and Type I responses for Apatemon prey. Temperature did not alter the consumption rate of the amphipod predator. Trichobilharzia was likely consumed at similar proportions as Diplostomum; however, this could not be fully evaluated due to low replication. Whilst Type II responses of invertebrate predators are common to various invertebrate prey types, this is the first time a non-filter feeding predator has been shown to exhibit Type I response towards cercarial prey. The prey-specific consumption patterns of amphipods were related to cercarial distribution in the water column rather than to the size of cercariae or temperature influence. The substantial energy flow into food webs by non-host consumer organisms highlights the importance of understanding the mechanisms that modulate functional responses and direct predation in the context of parasitic organisms. [ABSTRACT FROM AUTHOR]

Исследования популяций литоральных видов позволяют выявить отклик экосистем глубоких озер на изменения климата и сигналы предстоящих в них нежелательных и необратимых изменений. Имеющиеся сведения о популяционных показателях массовых в литоральной зоне озера Арахлей амфипод голарктического Gammarus lacustris (Sars, 1863) и широко расселившегося байкальского Gmelinoides fasciatus (Stebbing, 1899) относятся к многоводным годам. В экстремально маловодные 2017 и 2018 гг. Gm. fasciatus и G. lacustris были наиболее многочисленными компонентами зообентоса литоральной зоны озера Арахлей. Максимум численности яйценосных самок Gm. fasciatus и G. lacustris приходится на начало июня. Появление молоди Gm. fasciatus и G. lacustris в 2018 г. происходило также в начале июня. В это же время в 2017 г. большинство самок амфипод находились на ранних стадиях развития отложенных яиц. Сезонная динамика размерной структуры популяции Gm. fasciatus в 2017 и 2018 гг. в целом подобна и характеризуется выраженными максимумами. Динамика размерной структуры G. lacustris различается по годам и свидетельствует о сложном размерно-возрастном составе популяции. Продолжительность жизненного цикла большей части особей Gm. fasciatus в озере Арахлей в экстремально маловодные 2017–2018 гг. составила 12–14 месяцев, G. lacustris — 13–14 месяцев. Влияния снижения уровня воды в озере с 2000 по 2017 г. на популяционные показатели амфипод не выявлено, что может быть обусловлено его небольшой величиной — на 10% от глубины озера в 2000 г. Выявленная вариабельность популяционных показателей в смежные годы при одном уровне воды показывает их чувствительность к изменению термического режима озера и погодных условий. По результатам исследования предлагаем смещение сроков созревания отложенных самками яиц, смещение сроков появления молоди и межгодовые изменения в размерной структуре популяций Gm. fasciatus и G. lacustris озера Арахлей в качестве индикаторов изменения литоральных сообществ озера и климата региона.

Prevalence of a parasite may be influenced by age of the habitat (= time available for hosts and parasites to colonize habitats), assemblage composition of host and non-host species, or biotic and abiotic habitat features. For a trophically transmitted parasite, the intermediate host may be consumed by both final hosts and 'dead-end' predators that are incompetent to host the parasite. We tested biotic and abiotic factors that might influence parasite prevalence in a freshwater host–parasite system using a dataset collected from 36 water bodies in the vicinity of Edmonton, Alberta, Canada. In this system, eggs of thorny-headed worms (Acanthocephala: Polymorphus spp.) are eaten by intermediate-host amphipods (Gammarus lacustris Sars), which are then consumed by final vertebrate hosts (certain aquatic birds and muskrats) and various non-host waterbird species. We found that acanthocephalan prevalence in amphipods was positively correlated with waterbody age and with abundance of final-host species. In contrast, abundance of the intermediate host G. lacustris was less important and was negatively correlated with parasite prevalence ('encounter-dilution effect'). Similarly, parasite prevalence showed a marginally significant and negative correlation with abundance of 'dead-end' Gammarus-eating birds. We conclude that in our study system, time available for colonization and abundance of final hosts are more important for parasite prevalence in intermediate hosts than is abundance of intermediate and dead-end hosts. [ABSTRACT FROM AUTHOR]

The amphipod Gammarus lacustris has been distributing in the Tibetan region with well-known uplifts of the Tibetan plateau. It is hence considered as a good model for investigating stress adaptations of the plateau. Here, we sequenced the whole-genome and full-length transcriptome of G. lacustris, and compared the transcriptome results with its counterpart Gammarus pisinnus from a nearby plain. Our main goal was to provide a genomic resource for investigation of genetic mechanisms, by which G. lacustris adapted to living on the plateau. The final draft genome assembly of G. lacustris was 5.07 gigabases (Gb), and it contained 443,304 scaffolds (>2 kb) with an N50 of 2,578 bp. A total of 8,858 unigenes were predicted in the full-length transcriptome of G. lacustris, with an average gene length of 1,811 bp. Compared with the G. pisinnus transcriptome, 2,672 differentially expressed genes (DEGs) were up-regulated and 2,881 DEGs were down-regulated in the G. lacustris transcriptome. Along with these critical DEGs, several enriched metabolic pathways, such as oxidative phosphorylation, ribosome, cell energy homeostasis, glycolysis and gluconeogenesis, were predicted to play essential roles in the plateau adaptation. In summary, the present study provides a genomic basis for understanding the plateau adaption of G. lacustris, which lays a fundamental basis for further biological and ecological studies on other resident aquatic species in the Tibetan plateau.

The previously undescribed dynamics of the heat shock protein HSP70 and subsequent lipid peroxidation products have been assessed alongside lactate dehydrogenase activity for Gammarus lacustris Sars, an amphipod species from the saltwater Lake Shira (Republic of Khakassia). Individuals were exposed to a gradual temperature increase of 1 °C/hour (total exposure duration of 26 hours) starting from the mean annual temperature of their habitat (7 °C) up to 33 °C. A complex of biochemical reactions occurred when saltwater G. lactustris was exposed to the gradual changes in temperature. This was characterized by a decrease in lactate dehydrogenase activity and the launching of lipid peroxidation. The HSP70 level did not change significantly during the entire experiment. In agreement with the concept of oxygen-limited thermal tolerance, an accumulation of the most toxic lipid peroxides (triene conjugates and Schiff bases) in phospholipids occurred at the same time and temperature as the accumulation of lactate. The main criterion overriding the temperature threshold was, therefore, the transition to anaerobiosis, confirmed by the elevated lactate levels as observed in our previous associated study, and by the development of cellular stress, which was expressed by an accumulation of lipid peroxidation products. An earlier hypothesis, based on freshwater individuals of the same species, has been confirmed whereby the increased thermotolerance of G. lacustris from the saltwater lake was caused by differences in energy metabolism and energy supply of nonspecific cellular stress-response mechanisms. With the development of global climate change, these reactions could be advantageous for saltwater G. lacustris. The studied biochemical reactions can be used as biomarkers for the stress status of aquatic organisms when their habitat temperature changes.

The amphipod Gammarus lacustris has been distributing in the Tibetan region with well-known uplifts of the Tibetan plateau. It is hence considered as a good model for investigating stress adaptations of the plateau. Here, we sequenced the whole-genome and full-length transcriptome of G. lacustris , and compared the transcriptome results with its counterpart Gammarus pisinnus from a nearby plain. Our main goal was to provide a genomic resource for investigation of genetic mechanisms, by which G. lacustris adapted to living on the plateau. The final draft genome assembly of G. lacustris was 5.07 gigabases (Gb), and it contained 443,304 scaffolds (>2 kb) with an N50 of 2,578 bp. A total of 8,858 unigenes were predicted in the full-length transcriptome of G. lacustris , with an average gene length of 1,811 bp. Compared with the G. pisinnus transcriptome, 2,672 differentially expressed genes (DEGs) were up-regulated and 2,881 DEGs were down-regulated in the G. lacustris transcriptome. Along with these critical DEGs, several enriched metabolic pathways, such as oxidative phosphorylation, ribosome, cell energy homeostasis, glycolysis and gluconeogenesis, were predicted to play essential roles in the plateau adaptation. In summary, the present study provides a genomic basis for understanding the plateau adaption of G. lacustris , which lays a fundamental basis for further biological and ecological studies on other resident aquatic species in the Tibetan plateau. [ABSTRACT FROM AUTHOR]

Cave animals provide a unique opportunity to study contrasts in phenotype and life history in strikingly different environments when compared to surface populations, potentially related to natural selection. As such, we compared a permanent cave-living Gammarus lacustris (L.) population with two lake-resident surface populations analyzing morphology (eye- and antennal characters) and life-history (size at maturity, fecundity and egg-size). A part of the cytochrome c oxidase subunit I gene in the mitochondrion (COI) was analyzed to contrast genetic relationship of populations and was compared to sequences in GenBank to assess phylogeography and colonization scenarios. In the cave, a longer life cycle was implied, while surface populations seemed to have a shorter life cycle. Egg size, and size at maturity for both sexes, were larger in the cave than in surface populations, while fecundity was lower in the cave than in surface populations. The cave population had longer first- and second antennae with more articles, longer first- and second peduncles, and fewer ommatidia than surface populations. The cold low-productive cave environment may facilitate different phenotypic and life-history traits than in the warmer and more productive surface lake environments. The trait divergences among cave and surface populations resembles other cave-surface organism comparisons and may support a hypothesis of selection on sensory traits. The cave and Lake Ulvenvann populations grouped together with a sequence from Slovenia (comprising one genetic cluster), while Lake Lille Lauarvann grouped with a sequence from Ukraine (comprising another cluster), which are already recognized phylogenetic clusters. One evolutionary scenario is that the cave and surface populations were colonized postglacially around 9 000–10 000 years ago. We evaluate that an alternative scenario is that the cave was colonized during an interstadial during the last glaciation or earlier during the warm period before onset of the last glaciation. [ABSTRACT FROM AUTHOR]

Temperature and salinity are important abiotic factors for aquatic invertebrates. We investigated the influence of different salinity regimes on thermotolerance, energy metabolism and cellular stress defense mechanisms in amphipods Gammarus lacustris Sars from two populations. We exposed amphipods to different thermal scenarios and determined their survival as well as activity of major antioxidant enzymes (peroxidase, catalase, glutathione S-transferase) and parameters of energy metabolism (content of glucose, glycogen, ATP, ADP, AMP and lactate). Amphipods from a freshwater population were more sensitive to the thermal challenge, showing higher mortality during acute and gradual temperature change compared to their counterparts from a saline lake. A more thermotolerant population from a saline lake had high activity of antioxidant enzymes. The energy limitations of the freshwater population (indicated by low baseline glucose levels, downward shift of the critical temperature of aerobic metabolism and inability to maintain steady-state ATP levels during warming) was observed, possibly reflecting a trade-off between the energy demands for osmoregulation under the hypo-osmotic condition of a freshwater environment and protection against temperature stress.

Abstract Lake Baikal, the world's most voluminous freshwater lake, has experienced unprecedented warming during the last decades. A uniquely diverse amphipod fauna inhabits the littoral zone and can serve as a model system to identify the role of thermal tolerance under climate change. This study aimed to identify sublethal thermal constraints in two of the most abundant endemic Baikal amphipods, Eulimnogammarus verrucosus and Eulimnogammarus cyaneus, and Gammarus lacustris, a ubiquitous gammarid of the Holarctic. As the latter is only found in some shallow isolated bays of the lake, we further addressed the question whether rising temperatures could promote the widespread invasion of this non‐endemic species into the littoral zone. Animals were exposed to gradual temperature increases (4 week, 0.8 °C/d; 24 h, 1 °C/h) starting from the reported annual mean temperature of the Baikal littoral (6 °C). Within the framework of oxygen‐ and capacity‐limited thermal tolerance (OCLTT), we used a nonlinear regression approach to determine the points at which the changing temperature‐dependence of relevant physiological processes indicates the onset of limitation. Limitations in ventilation representing the first limits of thermal tolerance (pejus (= “getting worse”) temperatures (Tp)) were recorded at 10.6 (95% confidence interval; 9.5, 11.7), 19.1 (17.9, 20.2), and 21.1 (19.8, 22.4) °C in E. verrucosus, E. cyaneus, and G. lacustris, respectively. Field observations revealed that E. verrucosus retreated from the upper littoral to deeper and cooler waters once its Tp was surpassed, identifying Tp as the ecological thermal boundary. Constraints in oxygen consumption at higher than critical temperatures (Tc) led to an exponential increase in mortality in all species. Exposure to short‐term warming resulted in higher threshold values, consistent with a time dependence of thermal tolerance. In conclusion, species‐specific limits to oxygen supply capacity are likely key in the onset of constraining (beyond pejus) and then life‐threatening (beyond critical) conditions. Ecological consequences of these limits are mediated through behavioral plasticity in E. verrucosus. However, similar upper thermal limits in E. cyaneus (endemic, Baikal) and G. lacustris (ubiquitous, Holarctic) indicate that the potential invader G. lacustris would not necessarily benefit from rising temperatures. Secondary effects of increasing temperatures remain to be investigated.

The cellular heat shock response (HSR) comprises transcriptomic and proteomic reactions to thermal stress. It was here addressed, how the proteomic, together with the transcriptomic HSR, relate to the thermal sensitivities of three cold-adapted but differently thermo-sensitive freshwater amphipod species. The proteomes of thermosensitive Eulimnogammarus verrucosus and thermotolerant Eulimnogammarus cyaneus , both endemic to Lake Baikal, and of thermotolerant Holarctic Gammarus lacustris were investigated upon 24 h exposure to the species-specific 10 % lethal temperatures (LT10). Furthermore, correlations of heat stress induced changes in proteomes (this study) and transcriptomes (previous study with identical experimental design) were examined. Proteomes indicated that the HSR activated processes encompassed (i) proteostasis maintenance, (ii) maintenance of cell adhesion, (iii) oxygen transport, (iv) antioxidant response, and (v) regulation of protein synthesis. Thermo-sensitive E. verrucosus showed the most pronounced proteomic HSR and the lowest correlation of transcriptomic and proteomic HSRs. For proteins related to translation (ribosomal proteins, elongation factors), transcriptomic and proteomic changes were inconsistent: transcripts were downregulated in many cases, with levels of corresponding proteins remaining unchanged. In the Eulimnogammarus species, levels of hemocyanin protein but not transcript were increased upon heat stress, suggesting a HSR also directed to enhance oxygen transport. Thermosensitive E. verrucosus showed the most pronounced relocation of transcription/translation activity to proteostasis maintenance, which may indicate that the general species-specific stability of protein structure could be a fundamental determinant of thermotolerance. By combining transcriptomic and proteomic response data, this study provides a comprehensive picture of the cellular HSR components in the studied amphipods. [Display omitted] • Comparison of proteomic and transcriptomic heat shock responses (HSR) in amphipods • Most of protein HSR relates to maintenance of protein integrity and cell adhesion. • Correlation of transcriptomic and proteomic HSR is lower in more thermosensitive species. • Hemocyanin upregulated in proteomic HSR only. [ABSTRACT FROM AUTHOR]

Lake Baikal, the world's most voluminous freshwater lake, has experienced unprecedented warming during the last decades. A uniquely diverse amphipod fauna inhabits the littoral zone and can serve as a model system to identify the role of thermal tolerance under climate change. This study aimed to identify sublethal thermal constraints in two of the most abundant endemic Baikal amphipods, Eulimnogammarus verrucosus and Eulimnogammarus cyaneus, and Gammarus lacustris, a ubiquitous gammarid of the Holarctic. As the latter is only found in some shallow isolated bays of the lake, we further addressed the question whether rising temperatures could promote the widespread invasion of this non‐endemic species into the littoral zone. Animals were exposed to gradual temperature increases (4 week, 0.8 °C/d; 24 h, 1 °C/h) starting from the reported annual mean temperature of the Baikal littoral (6 °C). Within the framework of oxygen‐ and capacity‐limited thermal tolerance (OCLTT), we used a nonlinear regression approach to determine the points at which the changing temperature‐dependence of relevant physiological processes indicates the onset of limitation. Limitations in ventilation representing the first limits of thermal tolerance (pejus (= “getting worse”) temperatures (Tp)) were recorded at 10.6 (95% confidence interval; 9.5, 11.7), 19.1 (17.9, 20.2), and 21.1 (19.8, 22.4) °C in E. verrucosus, E. cyaneus, and G. lacustris, respectively. Field observations revealed that E. verrucosus retreated from the upper littoral to deeper and cooler waters once its Tp was surpassed, identifying Tp as the ecological thermal boundary. Constraints in oxygen consumption at higher than critical temperatures (Tc) led to an exponential increase in mortality in all species. Exposure to short‐term warming resulted in higher threshold values, consistent with a time dependence of thermal tolerance. In conclusion, species‐specific limits to oxygen supply capacity are likely key in the onset of constraining (beyond pejus) and then life‐threatening (beyond critical) conditions. Ecological consequences of these limits are mediated through behavioral plasticity in E. verrucosus. However, similar upper thermal limits in E. cyaneus (endemic, Baikal) and G. lacustris (ubiquitous, Holarctic) indicate that the potential invader G. lacustris would not necessarily benefit from rising temperatures. Secondary effects of increasing temperatures remain to be investigated. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the distribution patterns, genetic diversity and phylogenetic affinities and colonization histories of freshwater amphipods across the Tibetan Plateau based on a sampling and genetic data from two mitochondrial markers. Topics include a description of the Holarctic amphipod genus Gammarus and the sampling sites of Gammarus lacustris.

Gammarus lacustris is native to the Qinghai–Tibet Plateau (QTP), widely distributed in alpine lakes. The complete mitochondrial DNA sequence of G. lacustris was 15,349 base pairs in length and comprised 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 control region. The BI tree showed that G. lacustris was most closely related to Gammarus duebeni, and indicated that Gammarus, Gmelinoides, Brachyuropus, Pallaseopsis, and Eulimnogammarus evolved from a common ancestor. The mitogenome of G. lacustris provides new molecular data for further taxonomic and phylogenetic studies of Amphipoda. [ABSTRACT FROM AUTHOR]

We determined the amphipod population characteristics from the water bodies of the delta of the Selenga River, where Gammarus lacustris Sars, 1863 was industrially harvested until the 1990s. In 2011, the population density of G. lacustris varied from 80 to 10200 in Lapkhai Lake and from 80 to 2320 ind./m in Krivaya Channel. The low population density (<40 ind./m) in Gryaznoe Lake, together with the absence of the species in the waters of the former Zhilishchenskoe Lake, confirms the indications of population density decline in the associated waters of the delta. Population growth of G. lacustris was limited primarily by changes in the hydromorphology of the lakes and waterways due to floods of the early 1990s and the subsequent period of extremely low flow of the Selenga River. [ABSTRACT FROM AUTHOR]

Recent studies highlight the need to include estimates of detection/capture probability in population studies. This need is particularly important in studies where detection and/or capture probability is influenced by parasite-induced behavioral alterations. We assessed potential biases associated with sampling a population of the amphipod Gammarus lacustris in the presence of Polymorphus spp. acanthocephalan parasites shown to increase positive phototaxis in their amphipod hosts. We trapped G. lacustris at two water depths (benthic and surface) and compared number of captures and number of parasitized individuals at each depth. While we captured the greatest number of G. lacustris individuals in benthic traps, parasitized individuals were captured most often in surface traps. These results reflect the phototaxic movement of infected individuals from benthic locations to sunlit surface waters. We then explored the influence of varying infection rates on a simulated population held at a constant level of abundance. Simulations resulted in increasingly biased abundance estimates as infection rates increased. Our results highlight the need to consider parasite-induced biases when quantifying detection and/or capture probability in studies of aquatic invertebrate populations. [ABSTRACT FROM AUTHOR]

The large-male mating advantage and size-assortative mating are two different size-based patterns which deviate from random mating inGammarusspecies. The size-assortative pairing in gammarid amphipods may have arisen for microhabitat segregation, loading constraints, sexual selection, or a combination of them. This study investigated the mating patterns ofGammarus lacustrisfrom three populations along an altitudinal gradient in the northeastern Tibetan plateau. We demonstrated that the species shows a size-related non-random mating pattern. There is a strong sexual size dimorphism (SSD) inG. lacustris, which does not vary along the altitudinal gradient. The ultimate cause of male-biased SSD is likely the stronger selection acting on male than on female body size, either because large males have a higher mating success than smaller males (large male advantage at the highest elevation population), or because they mate with larger females with more fecundity in three populations, or both, which results in size-assortative mating ofG. lacustris. Additionally, the loading constraint hypothesis (size-assortative patterns potentially increased their fitness in fast-flowing water) cannot be excluded. [ABSTRACT FROM AUTHOR]

The physico-chemical characteristics of the Lake Baikal ecosystem classify it as an oxidative environment. Hydrogen peroxide (H2O2) is often used for the simulation of the responses of hydrobionts to oxidative stress conditions. Here we studied the survival rate and behavioural reactions of several species of amphipods from Lake Baikal and, for reference, Holarctic Cammarus lacustris in the presence of H2O2. Preference and avoidance reactions to H2O2 were estimated in special flow installations with pairwise choices. The amphipods were ranked by their degree of preference to H2O2 (in descending order) as: Eulimnogammarus vittatus = E. verrucosus > Pallasea cancellus > Gmelinoides fasciatus ⩾ G. lacustris. The deep-dwelling Ommdtogammarus flavus showed neither preference, nor avoidance reactions to the introduction of H2O2. A direct correlation was revealed between die survival rate of amphipods in H2O2 solutions and their body size. The smaller their body size, the less resistance was demonstrated by the species: E. verrucosus > E. vittatus ⩾ G. lacustris > E. cyaneus > G. fasciatus. The results of both series of experiments gave evidence that under conditions in which an active choice was possible, G. lacustris demonstrated a higher sensitivity to H2O2, than the Baikalian species we studied. Possible relations between die reactions discovered for the Baikalian amphipods, their living environment, and their possible expansion beyond Lake Baikal are discussed [ABSTRACT FROM AUTHOR]

1. Benthic chironomid larvae and the amphipod Gammarus lacustris have been observed in the pelagic habitats of many mountain lakes. The main goal of this study was to determine if chironomid larvae and gammarids potentially affect predator-prey and nutrient dynamics in pelagic food webs of mountain lakes. 2. Eighty-six mountain lakes were surveyed in Alberta and eastern British Columbia during the years 1965-1984, 1991-2004 and 2005-2007. Pelagic chironomid larvae were found in 86% of these lakes, and pelagic gammarids were found in 29% of lakes. Densities of pelagic chironomid larvae were 92% lower in lakes with pelagic gammarids and 76% lower in lakes with trout ( P < 0.05). Intraguild predation of trout on gammarids appeared to reduce predation pressure on chironomid larvae. Gammarids consumed in vitro about 1 chironomid per gammarid per day or about 20% of their body mass in chironomid biomass per day. 3. Concentrations of total dissolved P and N, particulate C, and chlorophyll-a increased with increasing densities of pelagic gammarids and chironomid larvae in situ ( R = 0.14 ± 0.19 SD, P < 0.1) and in vitro ( P < 0.001). 4. Our findings suggest that gammarids and chironomid larvae are linked as predators and prey in pelagic food webs, possibly stimulating phytoplankton abundance via nutrient release. [ABSTRACT FROM AUTHOR]

This paper focuses on the life-history, size- and sexual structure, and reproductive variables of the freshwater amphipod Gammarus lacustris from two small lakes in northern Russia, which differ in the presence/absence of the perch, Perca fluviatilis. The size of ovigerous females, the number of eggs at stages 2 (E2) and 7 (E7), egg mortality, fecundity index, and reproductive capacity were studied. The results obtained show that no significant differences exist in the size-dependent number of eggs (from 8 to 44 eggs per female in the size range of 7-18 mm) between the two G. lacustris populations studied. Those variables were approximated by a power function, as: lake with perch: E2 = 0.092 L2.17 (R2 = 0.59, n = 63); and perch-less lake: E2 = 0.106 L2.16 (R2 = 0.79, n = 41). For females in the body length (weight) range of 10-14 mm (20-40 mg), E2 averaged 69% of E7. There was no significant difference in the total abundance of the amphipod between lake with perch and perch-less lake. At the same time, a distinct effect of the presence of perch on the reproductive potential of G. lacustris was detected, primarily as a result of a decline in size of the egg-bearing females, and in clutch sizes, averaging 10.7 mm in the case of perch presence, versus 12.2 mm in the absence of that predator, and in 16 instead of 25 eggs per female, respectively. This difference in the reproductive capacity of G. lacustris between the studied lakes may be caused by selective perch predation, mainly on larger specimens of the gammarid (>8 mm body length). On the other hand, the females started to reproduce at smaller body sizes (7 mm) under predator exploitation than in the absence of the perch (9 mm). This 'early reproduction' can be considered an adaptation, raising the reproductive success of the amphipod, and some mechanism regulating the population size of G. lacustris under fish predation pressure. [ABSTRACT FROM AUTHOR]

Gammarus lacustris and Hyalella azteca (hereafter G. lacustris and H. azteca, respectively) are important components of secondary production in wetlands and shallow lakes of the upper Midwest, USA. Within the past 50 years, amphipod densities have decreased while occurrences of fish and intensity of agricultural land use have increased markedly across this landscape. We investigated influences of fish, sedimentation, and submerged aquatic vegetation (SAV) on densities of G. lacustris and H. azteca in semipermanent and permanent wetlands and shallow lakes ( n = 283) throughout seven eco-physiographic regions of Iowa, Minnesota, and North Dakota during 2004-2005. G. lacustris and H. azteca densities were positively correlated with densities of SAV ( P < 0.001 and P < 0.001, respectively). Both species were negatively correlated with densities of large fish (non-Cyprinidae; P = 0.01 and P = 0.013, respectively) and with high densities of fathead minnows ( Pimephales promelas; P < 0.001 and P = 0.033, respectively). H. azteca densities also were negatively correlated with densities of small fish (e.g., other minnows [Cyprinidae] and sticklebacks [Gasterosteidae]; P = 0.048) and common carp ( Cyprinus spp.; P = 0.022). G. lacustris densities were negatively correlated with high levels of suspended solids (an index for sedimentation; P < 0.001). H. azteca densities were positively correlated with the width of upland-vegetation buffers ( P = 0.004). Our results indicate that sedimentation and fish reduce amphipod densities and may contribute to the current low densities of amphipods in the upper Midwest. Thus, removing/excluding fish, and providing a thick buffer of upland vegetation around wetlands may help restore amphipod densities and wetland and water quality within this landscape. [ABSTRACT FROM AUTHOR]

Reproductive traits of seven amphipods from northern parts of Iran at 11 localities were studied in order to find feasible species for usage in aquaculture industries. The results revealed that the breeding season for Gammarus lacustris and G. paricrenatus from high latitudes was limited to a few months from May to June. Breeding activity of G. komareki from some springs was observed throughout the year, while Obesogammarus acuminatus and G. aequicauda from southern wetlands of the Caspian Sea and Pontogammarus maeoticus and P. borceae from southern Caspian sea shore showed various patterns. The mean egg number of O. acuminatus and G. aequicauda species was the highest with 49.8 and 37.7, respectively, while this value for G. komareki and P. maeoticus was the lowest with an average of 8.8 eggs. Reproductive strategy was found to be related to habitat characteristics such as chemical factors, substrate status, and the epifaunal living. [ABSTRACT FROM AUTHOR]

The paper presents the materials of a comparative study of characteristics of anaerobic mechanisms use under the conditions of lowered oxygen content by Baikal amphipods Eulimnogammarus vittatus (Dyb.), E. cyaneus (Dyb.), as well as by Palearctic Gammarus lacustris Sars. It is shown that the system of anaerobic metabolism works most effectively for Palearctic G. lacustris. This species is characterized by the least degree of use of low-efficient way of energy production-anaerobic lipolysis, and the highest degree of use of the most efficient way of energy production under the conditions of low oxygen content-anaerobic succinate production. For the Baikal species that are less resistant to the lowered level of oxygen we show more expressed induction of anaerobic lipolysis and lower degree of engagement of anaerobic succinate production. The degree of development of anaerobic processes in amphipods determines the degree of resistance to hypoxia and is related to ecological characteristics of the species. [ABSTRACT FROM AUTHOR]

The vertical distribution and abundance of Gammarus lacustris in the pelagic zone of two fishless meromictic lakes, L. Shira and L. Shunet, in Southern Siberia (Russia), was studied with the underwater video recording system and using vertical hauls. In both lakes, during summer stratification, Gammarus was distributed non-homogenously, with a stable peak in the metalimnion. The average depth of Gammarus population in the pelagic zone was significantly correlated with the depth of the thermocline. Gammarus abundances obtained using vertical plankton hauls with net were quite comparable with those obtained from video records. The peak abundance of Gammarus in the pelagic zone of the lakes observed with underwater video amounted up to 400 individuals m, while the peak animal densities in the metalimnion reached 50 ind. m. The data are compared with previously published abundances of Gammarus in the littoral of Lake Shira. Both littoral and pelagic can be equally important habitats for amphipods in meromictic lakes. The absence of fish in the pelagic zone, high oxygen concentration, low water temperature, increased seston concentration, elevated water density in the metalimnion and the anoxic hypolimnion can be the most probable combination of factors that are responsible for the peak of Gammarus in the metalimnion of these lakes. [ABSTRACT FROM AUTHOR]

We investigated the predatory effects of Dytiscus alaskanus, a large predaceous diving beetle, on the biomass, species composition and diversity of fishless pond communities. The effects were tested using presence and absence treatments of D. alaskanus in 24 mesocosms distributed among six ponds. We sampled phytoplankton, zooplankton and macroinvertebrates every two weeks for a six week period. Periphyton was sampled from the mesocosm walls on the final day. Total macroinvertebrate biomass decreased in the presence of dytiscids while species richness was not affected. Macroinvertebrate predators, snails and Gammarus lacustris decreased in the dytiscid treatments. Laboratory feeding experiments confirmed feeding preferences consistent with the mesocosm results. Periphyton biomass was six times greater in the dytiscid enclosures, concomitant with the decreased grazing by gastropods and other invertebrate primary consumers indicating a benthic trophic cascade. Top–down effects of dytiscids on other predatory invertebrates led to increased total zooplankton biomass, largely due to increased abundances of large and small cladocerans. Zooplankton species richness increased in the dytiscid enclosures. Inconsistent with trophic cascade theory, phytoplankton did not respond to top–down effects of D. alaskanus within the study period. Overall, the results show D. alaskanus predation caused trophic effects via two distinct food chains, a dytiscid–snail–periphyton trophic cascade, and a dytiscid–predatory macroinvertebrates–zooplankton partial trophic cascade. [ABSTRACT FROM AUTHOR]

Abstract: This study comparatively evaluated small heat shock proteins (sHSP) (related to α-crystallin) and antioxidant enzymes such as peroxidase (POD), catalase (CAT), glutathione S-transferase (GST) as anti-thermal stress response in two contrasting freshwater amphipods, the stenoecious Baikalean endemic Eulimnogammarus cyaneus and the Palearctic Gammarus lacustris. The thermal stress modulated the activity of antioxidant enzymes as well as the sHSP synthesis in both species. In both species, only the declining POD activity showed a clear dependency on exposure time. The most expressed response to elevated temperatures has been the activation of sHSP synthesis, with clear differences in the patterns: in G. lacustris, sHSP concentrations peaked after 12h with a subsequent decline, while they increased steadily in E. cyaneus. Hence, the stenoecious species did not acclimate to the thermal stress within the given exposure time as the euryecious did. [Copyright &y& Elsevier]

North-American Gammarus tigrinus and Ponto-Caspian Chelicorophium curvispinum are the most recently arrived exotic species in the benthic fauna of the Estonian coastal sea. Gammarus tigrinus was found for the first time in Kõiguste Bay, northern Gulf of Riga, in 2003. The range expansion of G. tigrinus was extremely rapid and by 2005 the species was found all over the northern Gulf of Riga. Chelicorophium curvispinum was found for the first time near Sillamäe, eastern Gulf of Finland, in 2005. The nearest established populations of these species are located in the Curonian Lagoon, Lithuania. In connection with the range expansion survey of G. tigrinus the rare gammarids of the Estonian coastal sea G. duebeni and G. lacustris were found in marginal coastal habitats, e.g. isolated bays and small coastal pools of the northern Gulf of Riga in 2005. [ABSTRACT FROM AUTHOR]

The data on Gammarus lacustris Sars, 1863 ecology in Transbaikalian water bodies was integrated by the example of Lakes Khalanda, Bain-Tsagan, Arakhlei, Zun-Torei, and Bain-Bulak. The impact of the major environmental factor on the pattern of G. lacustris spatial distribution, linear size, growth rate, time of reaching sexual maturity, and number of reproduced generations was shown. The role of G. lacustris in the ecosystem of studied water bodies was evaluated and the adaptive significance of the revealed life strategies was considered. [ABSTRACT FROM AUTHOR]

High mortality rates due to predation from fish may reduce densities of preferred prey animals. Predation may also depress the rate of recovery from environmental stress. In an alpine ecosystem damaged by acidification, we compared three different techniques of monitoring the recovery of two large species of crustaceans, the amphipod Gammarus lacustris and the notostrachan Lepidurus arcticus. The methods used were: (1): benthic littoral kick samples, (2): artificial substrate in the form of jute bags, (3): examination of brown trout stomachs. The monitoring took place in two limed lakes at the Hardangervidda mountain plateau in Central Norway, L. Svartavatn and L. Svartavasstjørni. Brown trout, Salmo trutta, is the only fish species in the lakes. Liming as a water quality improvement measure was started in 1994. All stomach samples were negative with respect to Gammarus and Lepidurus during the period 1987–1998. In 1999, the first records of both species were done in trout stomachs collected from Lake Svartavatnet. In Lake Svartavasstjørni, Lepidurus and Gammarus reappeared in fish stomachs in 2001 and 2002, respectively. During the period of monitoring, no records of these crustaceans were done in benthic samples and on artificial substrate in any of the two lakes. In an unacidified reference site, Lake Skiftesjøen, both benthic samples and the jute bags indicated a dense population of Gammarus. Our results strongly indicate that studies of fish stomachs are the best method for monitoring low-density populations of attractive fish food animals. [ABSTRACT FROM AUTHOR]