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Sami Souissi - One of the best experts on this subject based on the ideXlab platform.
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Complete mitochondrial genome of the calanoid copepod Eurytemora affinis (Calanoida, Temoridae)
Mitochondrial DNA Part B, 2019Co-Authors: Beom-soon Choi, Daesik Hwang, Atsushi Hagiwara, Jeonghoon Han, Sami Souissi, Jaeseong LeeAbstract:The complete mitochondrial genome was sequenced from the calanoid copepod Eurytemora affinis. The sequenced total genome size was 18,553 bp. The mitochondrial genome of E. affinis has 13 protein-co...
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Population response of the estuarine copepod Eurytemora affinis to its bioaccumulation of trace metals
Chemosphere, 2019Co-Authors: Mahammed Zidour, Zakia Boubechiche, Yen-ju Pan, Capucine Bialais, Benoit Cudennec, Thierry Grard, Djamel Drider, Christophe Flahaut, Baghdad Ouddane, Sami SouissiAbstract:Abstract We evaluated the acute toxicities of metals cadmium (Cd), copper (Cu) and nickel (Ni) to a widely-distributed copepod Eurytemora affinis isolated from the Seine estuary. Both sexes of adult E. affinis were exposed separately to the three metals at concentration gradients to determine its 50% lethal concentration (LC50). After 4 days of exposure, both males and females showed a higher sensitivity to Cu (male LC50: 25.0 μg.L−1 and female LC50: 38.0 μg.L−1) than to Ni (male LC50: 90.0 μg.L−1 and female 161.0 μg.L−1) and Cd (male LC50: 127.8 μg.L−1 and female LC50: 90.0 μg.L−1). To assess for the first time, the extend of metal bioaccumulation and its effect at population scale, late stages (>200 μm) were collected and exposed to each metal at the concentration of 1/3 LC50, and to their mixture during 144 h without feeding. The Cd concentration consistently increased with time until the end of the experiment, whereas the Ni and Cu concentrations reached a plateau after 24 h and 72 h exposure, respectively. The results revealed that the copepods could accumulate Cu faster than Ni and Cd either in the treatment alone (0.58 L g−1.d−1) or in the three-metal mixture (0.72 L g−1.d−1) after 50% of exposure time (72 h). The number of individuals decreased in copepod populations except for the Cd treatment, where the number of nauplii increased. In addition, all treatments of metal exposure negatively affected bacterial densities in the copepod cultures, where the Cu treatment showed a negative remarkable effect compared with Cd and Ni treatment did.
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Life in sympatry: coexistence of native Eurytemora affinis and invasive Eurytemora carolleeae in the Gulf of Finland (Baltic Sea)
Oceanologia, 2019Co-Authors: Natalia Sukhikh, Sami Souissi, Anissa Souissi, Anne-catherine Holl, Nikolaos V. Schizas, Victor R. AlekseevAbstract:Summary The invasion of exotic species into native ecosystems is becoming a crucial issue in global biology. Over the last ten years, at least 45 invasions of aquatic species have been reported in the eastern part of the Gulf of Finland; the majority of them were introduced through ballast water. Recently, invasion of the estuarine calanoid copepod Eurytemora carolleeae (Temoridae), originating from North America, has been reported in several European estuaries and particularly in the Gulf of Finland. This species is morphologically very similar to the native Eurytemora affinis, but it is easily discriminated by molecular markers. In this study, we monitored the distribution area of the invasive copepod species in European waters, as well as the population structure of (native) E. affinis and (invasive) E. carolleeae, from 2006 to 2018 in the Gulf of Finland. The population density of E. affinis was significantly higher, compared to E. carolleeae, during most of the study period. The only exception was Neva Bay in 2010, wherein the invasive species dominated possibly due to high temperatures and differences in the levels of fish predation. The reproductive performance of E. carolleeae was also higher than that of E. affinis. These results show different population dynamics between the two species. It was revealed that invasive E. carolleeae develops in some of the very same habitats as native E. affinis, thereby potentially becoming a significant component of the zooplankton in the studied area. Moreover, invader has the potential to displace native E. affinis.
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Life in sympatry: coexistence of native Eurytemora affinis and invasive Eurytemora carolleeae in the Gulf of Finland (Baltic Sea)
Elsevier, 2019Co-Authors: Natalia Sukhikh, Sami Souissi, Anissa Souissi, Anne-catherine Holl, Nikolaos V. Schizas, Victor AlekseevAbstract:Summary: The invasion of exotic species into native ecosystems is becoming a crucial issue in global biology. Over the last ten years, at least 45 invasions of aquatic species have been reported in the eastern part of the Gulf of Finland; the majority of them were introduced through ballast water. Recently, invasion of the estuarine calanoid copepod Eurytemora carolleeae (Temoridae), originating from North America, has been reported in several European estuaries and particularly in the Gulf of Finland. This species is morphologically very similar to the native Eurytemora affinis, but it is easily discriminated by molecular markers. In this study, we monitored the distribution area of the invasive copepod species in European waters, as well as the population structure of (native) E. affinis and (invasive) E. carolleeae, from 2006 to 2018 in the Gulf of Finland. The population density of E. affinis was significantly higher, compared to E. carolleeae, during most of the study period. The only exception was Neva Bay in 2010, wherein the invasive species dominated possibly due to high temperatures and differences in the levels of fish predation. The reproductive performance of E. carolleeae was also higher than that of E. affinis. These results show different population dynamics between the two species. It was revealed that invasive E. carolleeae develops in some of the very same habitats as native E. affinis, thereby potentially becoming a significant component of the zooplankton in the studied area. Moreover, invader has the potential to displace native E. affinis. Keywords: Eurytemora species, Copepoda, Zooplankton, Invasive and native species, Gulf of Finlan
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isolated populations of Eurytemora americana williams crustacea copepoda in the white sea rock pools postglacial relicts or anthropogenic invasions
Russian Journal of Biological Invasions, 2016Co-Authors: Natalia Sukhikh, Sami Souissi, Vincent Castric, N V Polyakova, Victor R. AlekseevAbstract:Molecular-genetic study of isolated populations of Eurytemora in the White Sea showed its undoubted proximity to the native North American populations of Eurytemora americana, Williams 1906. Genetic tests show the recent colonization of the White Sea rock pools by initially small amount of individuals of E. americana. Existing published data on the presence of isolated Atlantic and Pacific species in the Arctic region are mostly explained by historical reasons: preservation of relict populations formerly inhabited the Holarctic and separated by processes of formation and melting of glaciers. Finding of E. americana in the White Sea allowed us to suppose a possible reason of formation of these isolates: transportation with ship ballast waters during the period of intensive cargo in the Second World War along the edge of the Arctic seas.
Jiang-shiou Hwang - One of the best experts on this subject based on the ideXlab platform.
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Swimming kinematics of Eurytemora affinis (Copepoda, Calanoida) reproductive stages and differential vulnerability to predation of larval Dicentrarchus labrax (Teleostei, Perciformes)
Journal of Plankton Research, 2011Co-Authors: Mohamed Sofiane Mahjoub, Sami Souissi, Francois-gaël Michalec, Francèois G. Schmitt, Jiang-shiou HwangAbstract:In egg-bearing copepods, the ovigerous females are reported to be more vulnerable to predators. However, the underlying mechanistic details of increased vulnerability are not yet well understood. We studied the predator-prey interaction between the copepod prey Eurytemora affinis and a predator, post-larvae of the sea bass Dicentrarchus labrax. Standard video techniques have been used to quantify the predation efficiency of larval sea bass and to record the two-dimensional swimming behavior of the different reproductive stages (males, non-ovigerous females and ovigerous females) of E. affinis in both the absence and presence of predators. Our results revealed that ovigerous females suffered higher mortality rates than either non-ovigerous females or males. Body size and swimming speed seemed to be the main determinants of prey conspicuuousness to predators. In the light of published data, we conclude that acute vulnerability of E. affinis ovigerous females to planktivorous predators is not necessarily harmful at the population level.
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Changes in the swimming behavior of Eurytemora affinis (Copepoda, Calanoida) in response to a sub-lethal exposure to nonylphenols.
Aquatic Toxicology, 2011Co-Authors: Kévin Cailleaud, Joëlle Forget-leray, Francois-gaël Michalec, Hélène Budzinski, Jiang-shiou Hwang, François G Schmitt, Sami SouissiAbstract:Estuarine waters are continuously loaded with chemicals which affect the physiology of aquatic organisms to various extents. They also have adverse effects on a wide range of behaviors. Nonylphenols and related compounds are biodegradation products of the nonionic surfactants nonylphenol polyethoxylates. They are commonly found in the aquatic environment. We observed immediate alterations of the free swimming activity of the calanoid copepod Eurytemora affinis from the Seine estuary in response to a sub-lethal concentration of nonylphenols (4-NP and NP1EC) at environmentally realistic concentrations (2 μg/L). Swimming speed and activity increased for both males and females. The use of copepod kinematic proved to be a sensitive indicator of sub-lethal exposure to pollutants.
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Differences in behavioral responses of Eurytemora affinis (Copepoda, Calanoida) reproductive stages to salinity variations
Journal of Plankton Research, 2010Co-Authors: Francois-gaël Michalec, Sami Souissi, François G Schmitt, Gaël Dur, Mohamed Sofiane Mahjoub, Jiang-shiou HwangAbstract:Estuarine copepods experience strong and frequent salinity variations caused by alternating tides. Salinity is known to be a major parameter in the ecology of copepods from brackish waters but its effects on small scale behavior are relatively unclear. In this study, we used two-dimensional laboratory filming techniques to record swimming paths of the three reproductive stages (i.e. male, non-ovigerous female and ovigerous female) of Eurytemora affinis from the Seine estuary, under different salinity conditions. We show that the probability density of both the instantaneous swimming speed and the duration of the two most frequent swimming states (i.e. break and slow swimming) followed a power-law trend regardless of the salinity. Increase in salinity (i.e. 5, 15, 25 and 30) steadily decreased the instantaneous speed of E. affinis reproductive stages. At the extreme salinity of 0.5, the mean speed decreased for non-ovigerous females and ovigerous females but increased for males, when compared with higher salinities. Maximum speed was observed at salinity 0.5 for males and at salinity 5 for non-ovigerous females and ovigerous females. Low swimming speeds were associated with break events of high frequency and long duration. High swimming speeds were exhibited with cruising states of high frequency and break events of short duration. This supports laboratory and field studies indicating a preference of E. affinis for low to medium salinities.
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Life cycle traits of two transatlantic populations of Eurytemora affinis (Copepoda: Calanoida): salinity effects
Journal of Plankton Research, 2009Co-Authors: Delphine Beyrend-dur, Sami Souissi, Gesche Winkler, David Devreker, Jiang-shiou HwangAbstract:While the populations of the copepod Eurytemora affinis are often morphologically (i.e. taxonomy) indistinguishable, the species complex is composed of genetically distinct clades, representing divergent evolutionary histories. The most distant clades, genetically and morphologically (i.e. phylogeny), are transatlantic clades: North American and European (Lee, 2000). The study of the life cycle strategies of two populations from St. Lawrence salt-marshes (Canada) and from the Seine estuary (France) at three salinities (5, 15 and 25) revealed differences in their salinity tolerance. Individual from the Seine exhibited high mortality under the highest salinity suggesting that the St. Lawrence population tolerated a wider salinity range. At the lowest salinity, the development time of St. Lawrence individuals was longer than that of individuals from the Seine suggesting that the Seine population was more adapted to low salinity. The clutch size and the longevity of St. Lawrence adults were on average two times higher compared to Seine adults. Thus, the St. Lawrence population exhibited a higher fitness relative to the Seine population. Such differences could be due to genetic differences resulting from divergent evolutionary history, to phenotypic plasticity and/or to the acclimation to culture conditions. We confirmed that a gamma density function is an appropriate fitting function for copepod development time, based on a large data set on development time. It can therefore be integrated into individual-based models of copepod population dynamics.
Carol Eunmi Lee - One of the best experts on this subject based on the ideXlab platform.
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MARGINAL OVERDOMINANCE SURVIVAL DATA
2016Co-Authors: Marijan Posavi, Gregory William Gelembiuk, Bret Larget, Carol Eunmi LeeAbstract:This dataset was generated by an experiment performed by Marijan Posavi to test for the presence of reversal of dominance and marginal overdominance in salinity tolerance in the salt-to-freshwater invading copepod Eurytemora affinis. Saline and freshwater inbred lines were crossed to determine survival of the F1 hybrids relative to each parental line at three salinities. This research was performed in the laboratory of Carol Eunmi Lee at the University of Wisconsin, and was funded by the National Science Foundation
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Evolutionary mechanisms of habitat invasions, using the copepod Eurytemora affinis as a model system.
Evolutionary Applications, 2015Co-Authors: Carol Eunmi LeeAbstract:The study of the copepod Eurytemora affinis has provided unprecedented insights into mechanisms of invasive success. In this invited review, I summarize a subset of work from my laboratory to highlight key insights gained from studying E. affinis as a model system. Invasive species with brackish origins are overrepresented in freshwater habitats. The copepod E. affinis is an example of such a brackish invader, and has invaded freshwater habitats multiple times independently in recent years. These invasions were accompanied by the evolution of physiological tolerance and plasticity, increased body fluid regulation, and evolutionary shifts in ion transporter (V-type H(+) ATPase, Na(+), K(+)-ATPase) activity and expression. These evolutionary changes occurred in parallel across independent invasions in nature and in laboratory selection experiments. Selection appears to act on standing genetic variation during invasions, and maintenance of this variation is likely facilitated through 'beneficial reversal of dominance' in salinity tolerance across habitats. Expression of critical ion transporters is localized in newly discovered Crusalis leg organs. Increased freshwater tolerance is accompanied by costs to development time and greater requirements for food. High-food concentration increases low-salinity tolerance, allowing saline populations to invade freshwater habitats. Mechanisms observed here likely have relevance for other taxa undergoing fundamental niche expansions.
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Without Gills: Localization of Osmoregulatory Function in the Copepod Eurytemora affinis
Physiological and Biochemical Zoology, 2014Co-Authors: Kelsey E. Johnson, Lucile Perreau, Guy Charmantier, Mireille Charmantier-daures, Carol Eunmi LeeAbstract:AbstractThe Pancrustacea, which include crustaceans and hexapods, have successfully colonized marine, freshwater, and terrestrial habitats. While members of the class Malacostraca (e.g., crabs, shrimp) often display immense osmoregulatory capacities, more basally branching crustaceans (e.g., copepods, branchiopods) tend to possess less-specialized osmoregulatory structures that have been poorly characterized. Remarkably, some of these more basal taxa have also colonized diverse habitats. For instance, the copepod Eurytemora affinis has recently invaded freshwater habitats multiple times independently but lack obvious osmoregulatory structures. To explore localization of ion exchange, we performed silver staining, immunohistochemical staining, and transmission electron microscopy. Our results revealed localization of ion transport within the maxillary glands and on four pairs of swimming legs. Silver staining revealed ion exchange at the maxillary pores and on the endopods and exopods of swimming legs P1 t...
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out of alaska morphological diversity within the genus Eurytemora from its ancestral alaskan range crustacea copepoda
Hydrobiologia, 2010Co-Authors: Stanley I Dodson, Daniel A Skelly, Carol Eunmi LeeAbstract:The copepod genus Eurytemora occupies a wide range of habitat types throughout the Northern Hemisphere, with among the broadest salinity ranges of any known copepod. The epicenter of diversity for this genus lies along coastal Alaska, where several species are endemic. Systematic analysis has been difficult, however, because of a tendency toward morphological stasis in this genus, despite large genetic divergences among populations and species. The goals of this study were to (1) analyze patterns of morphological variation and divergence within this genus, focusing on Eurytemora species that occur in North America, and (2) determine patterns of geographic and salinity distribution of Eurytemora species within the ancestral range in Alaska. We applied a comparative multivariate morphological analysis using 16–26 characters from 125 specimens from 20 newly collected sites in Alaska and 15 existing samples predominantly from North America. Results from principal component and hierarchical cluster analyses identified seven distinct morphological species of Eurytemora in North America (E. affinis, E. americana, E. canadensis, E. composita, E. herdmani, E. pacifica, and E. raboti), and identified diagnostic characters that distinguish the species (forming the basis for a new identification key). Several previously named species were regarded as synonyms. The sites we sampled in Alaska were remarkable in the high levels of sympatry of Eurytemora species, to a degree not seen outside of Alaska. Future studies of Eurytemora should shed light on patterns of habitat invasions and physiological evolution within the genus, and yield insights into mechanisms leading to its remarkably broad geographic and habitat range.
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dna feulgen cytophotometric determination of genome size for the freshwater invading copepod Eurytemora affinis
Genome, 2004Co-Authors: Ellen M. Rasch, Carol Eunmi Lee, Grace A. WyngaardAbstract:Variation in nuclear DNA content within some eukaryotic species is well documented, but causes and consequences of such variation remain unclear. Here we report genome size of an estuarine and salt-marsh calanoid copepod, Eurytemora affinis, which has recently invaded inland freshwater habitats independently and repeatedly in North America, Europe, and Asia. Adults and embryos of E. affinis from the St. Lawrence River drainage were exam- ined for somatic cell DNA content and the presence or absence of embryonic chromatin diminution, using Feulgen- DNA cytophotometry to determine a diploid or 2C genome size of 0.6-0.7 pg DNA/cell. The majority of somatic cell nuclei, however, have twice this DNA content (1.3 pg/nucleus) in all of the adults examined and possibly represent a population of cells arrested at the G2 stage of the cell cycle or associated with some degree of endopolyploidy. Both suggestions contradict assumptions that DNA replication does not occur in adult tissues during the determinate growth characteristic of copepods. Absence of germ cell nuclei with markedly elevated DNA values, commonly found for spe- cies of cyclopoid copepods that show chromatin diminution, indicates that E. affinis lacks this trait. The small genome size and presumed absence of chromatin diminution increase the potential utility of E. affinis as a model for genomic studies on mechanisms of adaptation during freshwater invasions.
Michael R. Roman - One of the best experts on this subject based on the ideXlab platform.
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temperature impacts on Eurytemora carolleeae size and vital rates in the upper chesapeake bay in winter
Estuaries and Coasts, 2016Co-Authors: James J Pierson, David G. Kimmel, Michael R. RomanAbstract:The copepod Eurytemora carolleeae dominates vernal zooplankton biomass in the Chesapeake Bay estuarine turbidity maximum (ETM) region, where it is an important prey item for larval anadromous fish. Although there have been several zooplankton studies in the Chesapeake Bay ETM focused on spring, the importance of winter zooplankton populations for establishing these vernal conditions has not been investigated. We examined the abundance, distribution, and individual sizes of E. carolleeae in winter of 2007 and 2008 and we investigated the potential impact of varying winter conditions and rising winter temperatures on Eurytemora female carbon content, egg production rate, and generation time. We found higher abundances and larger individuals in the colder 2007 than in 2008 under similar freshwater flow conditions. Empirical estimates showed that overall zooplankton productivity was higher in 2007 than in 2008. Published recruitment indices for anadromous fish including white perch and striped bass were higher in 2007 than in 2008 in the study region. Based on these findings, we hypothesize that colder conditions resulted in larger individuals and therefore increased prey biomass available to larval fish. We further hypothesize that rising winter water temperatures will negatively impact trophic transfer of primary production to copepods and ultimately to fish.
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Egg production by the copepod, Eurytemora affinis, in Chesapeake Bay turbidity maximum regions
Journal of Plankton Research, 2013Co-Authors: Scott S. Lloyd, David T. Elliott, Michael R. RomanAbstract:The copepod, Eurytemora affinis, exhibits maximum abundance in estuarine turbidity maxima (ETMs) of estuaries around the world, including the Chesapeake Bay. We performed egg clutch size (CS) measurements of E. affinis to help understand why this copepod species reaches maximum abundance within ETM regions. Prosome length alone, without any measure of food quantity or quality, was the best predictor for egg CS. The relationship of CS with nutritional variables and the comparison of measured particulate organic carbon concentrations with food requirements predicted from bioenergetics models both suggest that E. affinis egg production is not food limited in Chesapeake Bay ETMs. In addition, nutrition indices based on the seston of the Chesapeake Bay and Choptank River ETMs suggest that food quality was sufficient to support the maximum E. affinis production. Thus, we postulate that abiotic factors, predation and advection limit E. affinis populations in the Chesapeake Bay ETM regions rather than food resources. In Chesapeake Bay ETMs, E. affinis egg production rates began to decrease when temperatures were above 188C which is similar to results found in laboratory experiments and may help explain the successional dominance switch from E. affinis in winter-spring to the copepod Acartia tonsa in summer.
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an experimental approach to estimate egg production and development rate of the calanoid copepod Eurytemora affinis in chesapeake bay usa
Journal of Experimental Marine Biology and Ecology, 2012Co-Authors: David Devreker, Sami Souissi, David G. Kimmel, James J Pierson, Michael R. RomanAbstract:Abstract The calanoid copepod Eurytemora affinis is the dominant copepod in Chesapeake Bay oligohaline regions and an important food source for larval fish, particularly during its early spring abundance peak. We measured life-history traits of E. affinis in cultures reared from Chesapeake Bay collections in food-saturated laboratory conditions at two temperatures (14° and 18 °C) and four salinities (1, 5, 15 and 21). We measured female life span, egg production, eggs produced over the life span, hatching success, mean clutch size, inter-clutch duration and nauplii survival. Adult females lived more than 2 months and produced more than 2500 eggs at 14 °C and salinity 5, with egg hatching success > 90%. Mean clutch size and inter-clutch time varied as a function of both temperature and adult senescence and ranged from 40 to 110 eggs clutch− 1 and 1.9 to 3.4 days, respectively. Egg production rate was also affected by adult senescence and averaged 37.8 eggs female− 1 day− 1 at 14 °C and salinity 5. Our results showed that E. affinis were adapted to cooler, fresher conditions more than the other dominant calanoid copepod in the Chesapeake Bay, Acartia tonsa, which has been shown to be well adapted to warmer temperatures and higher salinities. E. affinis exhibited better survival, development rate and naupliar production in lower temperatures and salinities compared to A. tonsa. At higher temperatures and salinities, E. affinis repeatedly released egg sacs with unhatched eggs prior to extrusion of a new egg sac. The dropped egg sacs contained eggs that were not yet hatched, a condition not observed in other species in the genus Eurytemora and which may indicate a potential cost of carrying eggs at higher temperatures.
Victor R. Alekseev - One of the best experts on this subject based on the ideXlab platform.
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copepod Eurytemora caspica sukhikh et alekseev 2013 crustacea calanoida in volga and kama river reservoirs
Inland Water Biology, 2020Co-Authors: Natalia Sukhikh, V I Lazareva, Victor R. AlekseevAbstract:In 2013, a new species, Eurytemora caspica Sukhikh et Alekseev, 2013, was described from the northern part of the Caspian Sea. A thorough morphological analysis of Eurytemora from the Volga River basin by the original descriptors of the species has shown that E. caspica, rather than previously assumed E. affinis, actually inhabits the studied area. The species E. affinis itself was not detected in any sample. Analysis of the mitochondrial cytochrome oxidase subunit 1 gene (COI) has confirmed the species status of the studied populations from the Caspian Sea and some other areas of the Volga basin. The species is widespread throughout the Volga basin to the Kama Reservoir at the confluence of the Inva and Kosva rivers (58°52′ N) in the north and has penetrated to the mouth of the Kama River (55°12′ N) upstream the Volga. During summer, the abundance of the species in different parts of the Volga–Kama basin ranged from single findings to several thousand species per cubic meter.
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Life in sympatry: coexistence of native Eurytemora affinis and invasive Eurytemora carolleeae in the Gulf of Finland (Baltic Sea)
Oceanologia, 2019Co-Authors: Natalia Sukhikh, Sami Souissi, Anissa Souissi, Anne-catherine Holl, Nikolaos V. Schizas, Victor R. AlekseevAbstract:Summary The invasion of exotic species into native ecosystems is becoming a crucial issue in global biology. Over the last ten years, at least 45 invasions of aquatic species have been reported in the eastern part of the Gulf of Finland; the majority of them were introduced through ballast water. Recently, invasion of the estuarine calanoid copepod Eurytemora carolleeae (Temoridae), originating from North America, has been reported in several European estuaries and particularly in the Gulf of Finland. This species is morphologically very similar to the native Eurytemora affinis, but it is easily discriminated by molecular markers. In this study, we monitored the distribution area of the invasive copepod species in European waters, as well as the population structure of (native) E. affinis and (invasive) E. carolleeae, from 2006 to 2018 in the Gulf of Finland. The population density of E. affinis was significantly higher, compared to E. carolleeae, during most of the study period. The only exception was Neva Bay in 2010, wherein the invasive species dominated possibly due to high temperatures and differences in the levels of fish predation. The reproductive performance of E. carolleeae was also higher than that of E. affinis. These results show different population dynamics between the two species. It was revealed that invasive E. carolleeae develops in some of the very same habitats as native E. affinis, thereby potentially becoming a significant component of the zooplankton in the studied area. Moreover, invader has the potential to displace native E. affinis.
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isolated populations of Eurytemora americana williams crustacea copepoda in the white sea rock pools postglacial relicts or anthropogenic invasions
Russian Journal of Biological Invasions, 2016Co-Authors: Natalia Sukhikh, Sami Souissi, Vincent Castric, N V Polyakova, Victor R. AlekseevAbstract:Molecular-genetic study of isolated populations of Eurytemora in the White Sea showed its undoubted proximity to the native North American populations of Eurytemora americana, Williams 1906. Genetic tests show the recent colonization of the White Sea rock pools by initially small amount of individuals of E. americana. Existing published data on the presence of isolated Atlantic and Pacific species in the Arctic region are mostly explained by historical reasons: preservation of relict populations formerly inhabited the Holarctic and separated by processes of formation and melting of glaciers. Finding of E. americana in the White Sea allowed us to suppose a possible reason of formation of these isolates: transportation with ship ballast waters during the period of intensive cargo in the Second World War along the edge of the Arctic seas.
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Genetic and morphological heterogeneity among populations of Eurytemora affinis (Crustacea: Copepoda: Temoridae) in European waters.
Comptes Rendus Biologies, 2016Co-Authors: Natalia Sukhikh, Sami Souissi, Gesche Winkler, Vincent Castric, Anissa Souissi, Anne-catherine Holl, Victor R. AlekseevAbstract:Our understanding of the systematics of the Eurytemora affinis complex developed at a fast pace over the last decades. Formerly considered as a complex of cryptic species, it is now believed to include three valid species: E. affinis, Eurytemora carolleeae, and Eurytemora caspica. American and European representatives have been studied in detail with respect to fine-scale geographic distribution, levels of genetic subdivision, evolutionary and demographic histories. Morphological components have been less explored. In this study, an analysis of the phylogeny and morphology of E. affinis was done, with a special focus on European populations. A total of 447 individuals of E. affinis from Europe were analyzed with genetic tools and 170 individuals according to morphological criteria. Common and new morphological and genetic features were analyzed. For this, we used ML and Bayesian methods to analyze the bar coding mt-DNA gene cytochrome c oxidase I subunit. Both genetic and morphological analyses showed high heterogeneities among the E. affinis populations from Europe. As a result, three local populations of E. affinis in Western Europe, including the European part of Russia, were established. Their genetic and morphological heterogeneity corresponded to the subspecies level.
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Cryptic or pseudocryptic: can morphological methods inform copepod taxonomy? An analysis of publications and a case study of the Eurytemora affinis species complex
Ecology and Evolution, 2015Co-Authors: Dmitry Lajus, Natalia Sukhikh, Victor R. AlekseevAbstract:Interest in cryptic species has increased significantly with current progress in genetic methods. The large number of cryptic species suggests that the resolution of traditional morphological techniques may be insufficient for taxonomical research. However, some species now considered to be cryptic may, in fact, be designated pseudocryptic after close morphological examination. Thus the “cryptic or pseudocryptic” dilemma speaks to the resolution of morphological analysis and its utility for identifying species. We address this dilemma first by systematically reviewing data published from 1980 to 2013 on cryptic species of Copepoda and then by performing an in-depth morphological study of the former Eurytemora affinis complex of cryptic species. Analyzing the published data showed that, in 5 of 24 revisions eligible for systematic review, cryptic species assignment was based solely on the genetic variation of forms without detailed morphological analysis to confirm the assignment. Therefore, some newly described cryptic species might be designated pseudocryptic under more detailed morphological analysis as happened with Eurytemora affinis complex. Recent genetic analyses of the complex found high levels of heterogeneity without morphological differences; it is argued to be cryptic. However, next detailed morphological analyses allowed to describe a number of valid species. Our study, using deep statistical analyses usually not applied for new species describing, of this species complex confirmed considerable differences between former cryptic species. In particular, fluctuating asymmetry (FA), the random variation of left and right structures, was significantly different between forms and provided independent information about their status. Our work showed that multivariate statistical approaches, such as principal component analysis, can be powerful techniques for the morphological discrimination of cryptic taxons. Despite increasing cryptic species designations, morphological techniques have great potential in determining copepod taxonomy.
