The state of the population of narrow-clawed crayfish in Lake Sevan (Armenia) under multiple stress conditions.

The narrow-clawed crayfish is a crayfish species that was accidentally introduced into the ecosystem of Lake Sevan in the 1980s. Soon it became one of the most preferred fisheries in the lake and an important link in the food chain by successfully replacing the endemic fish subspecies Sevan khramicarp (Capoeta sevangi, De Filippi, 1865) in the chain of detritivores. However, recently, the stock declines dramatically, associated with two main threats: the impact of burn-spot disease and an increase in fishing pressure on its population. To estimate the state of population under multiple stress conditions, we investigated the dynamics of stock, the size/age and sex structure, the fecundity, and the health status of the population. A comparative analysis of oxidative stress biomarkers (superoxide dismutase, catalase, glutathione-S-transferase activities and reduced glutathione, thiobarbituric acid reactive substance contents) showed significant differences between healthy and infected individuals. Another indirect effect of the disease, which probably leads to a decrease in the stock, was an increase in the proportion of immature females. Also, we observed some decrease in the infection rate along with the decline in the density of crayfish. However, stock reduction and some changes in the population may also be caused by a strong bloom of cyanobacteria.

Assessment of the mutagenic potential of the water of an urban river by means of two Tradescantia-based test systems.

River pollution can be caused by anthropogenic or natural factors. When testing water quality for the presence of toxic substances, higher plants as bioindicators for the genotoxic effects of complex mixtures are effective and appropriate. Hence, in this work the Tradescantia (clone 02) stamen hair mutations (Trad-SHM) and Tradescantia micronuclei (Trad-MCN) were used to determine mutagenic and clastogenic potential of an urban river. A significant increase in the level of all studied endpoints as well as morphological changes, including pink cells (PC) and colorless cells (CC) in stamen hairs, stunted hairs (SH), tetrads with micronuclei (MN) and MN in tetrads of pollen microspores in the Tradescantia was observed compared to the negative control (tap water). As an example riverine system, part of the River Hrazdan (Armenia) flowing through a highly urbanized and industrial area was studied. The positive control (10 mM CrO3) showed the highest genotoxicity for the SHM assay (PC: 5.1 / 1000, CC: 17.9 / 1000) and for the MCN assay (12 MN / 100 tetrads and 9.4 ± 0.53 tetrads with MN). Genetic responses were analyzed in conjunction with the concentrations of select elements in the riverine water. Reasons for observing such a high level of genetic markers in the riverine water and applicability of the Tradescantia (clone 02) test-systems in environmental risk assessment and biomonitoring are discussed.

Caucasian treasure: Genomics sheds light on the evolution of half-extinct Sevan trout, Salmo ischchan, species flock.

Five ecologically and phenotypically divergent ecomorphs of the genus Salmo are known from a landlocked alpine lake in the Caucasus, Lake Sevan. It is an example of sympatric diversification within a species-rich lineage with predominate mode of speciation being allopatric. The diversification of Sevan trouts was accompanied by spawning resource partitioning. Four lacustrine ecomorphs with different temporal-spatial spawning strategies and divergent morphology and coloration evolved along with a fifth ecomorph, brook trout, inhabiting the tributaries. Unfortunately, the Sevan trout diversity was almost destroyed by human activity, with two ecomorphs becoming extinct in the 1980s. We performed reconstruction of the evolutionary history of Sevan trouts based on high-throughput sequencing of both contemporary and historical DNA (∼ 50 y.o.) of all Sevan trout ecomorphs. Our study of complete mitogenomes along with genome-wide SNP data revealed the monophyly of four lacustrine ecomorphs and local brook trout, all derived from the anadromous form Caspian salmon, S. caspius. The species tree suggests a scenario of stepwise evolution from riverine to lacustrine spawning. Three genomic clusters were revealed, of which two refer to the riverine and lacustrine spawners within the flock of Sevan trouts (with FST value = 0.069). A few SNP outliers under selection were discovered that could be responsible for assortative mating based on visual recognition. The Holocene climatic oscillations and the desiccation of tributaries could have played an important role in the origin of lacustrine spawning. The relationships between lacustrine ecomorphs were not yet fully resolved. This radiation warrants further investigation.

Ingestion and effects of virgin polyamide microplastics on Chironomus riparius adult larvae and adult zebrafish Danio rerio.

Secondary microplastics (MP) produced by fragmentation of plastic in the environment or as a result of human activities can easily be taken up by organisms. The harmful effects of MP depend on e.g., the type, dimensions, sorption capacity and concentration of MP. In this study the ingestion of virgin irregularly-shaped polyamide microplastics (PA-MP; up to180 µm) by two different species was evaluated: 3rd - 4th instar larvae of midge Chironomus riparius and adult fish Danio rerio. More specifically, in the case of C. riparius larvae their feeding strategy, i.e. the ability to differentiate between food and non-food material (PA-MP) and the impact of pseudo-satiation by PA-MP on larval growth, development and emergence was evaluated. Two feeding regimes (with and without food supply) and two PA-MP concentrations (100 mg kg-1 and 1000 mg kg-1) were applied. Fish were exposed to two PA-MP concentrations (30 and 330 mg L-1) for 48 h followed by 48 h of depuration. The fish were fed during both periods. Both, chironomid larvae and adult zebrafish actively ingested PA-MP. Remarkably more PA-MP was ingested when larvae were not fed during the exposure to PA-MP. In the case of fish, the ingested particles were effectively evacuated from the gastrointestinal tract. Even the highest PA-MP concentrations did not cause obvious harmful effects to either species. The obtained data are informative for risk evaluation of PA-MP as polyamide is registered in the database of the European Chemicals Agency (ECHA) in the framework of the EU's REACH (Registration, Evaluation, Authorization & Restriction of Chemicals) regulation.

An integrative evaluation of suitability of a river for natural reproduction of trout of Lake Sevan (Armenia).

Endemic fish species of Armenian ichthyofauna-Sevan trout (Salmo ischchan Kessler, 1877)-is registered in the Red Book of Animals of the Republic of Armenia as "Critically Endangered" (corresponds to IUCN category: CR A2cd). Its natural reproduction hardly occurs as a result of numerous problems related to the use and management of water and bio-resources in the Lake Sevan drainage basin. Masrik River is formerly known as a spawning river for two ecological races of the Sevan trout, but there is no up-to-date and in-depth studies of its potential to support natural reproduction. Thus, a set of spawning criteria was arranged as matrix and state of Masrik River as spawning area for the Sevan trout was assessed. The results showed that the potential of different parts of Masrik River to support natural reproduction of Sevan trout varied from quite appropriate to inappropriate. The main limiting factors revealed were water temperature, velocity and substrate conditions.

Sequencing of two mitochondrial genomes of endangered form of the Sevan trout Salmo ischchan aestivalis.

The two complete mitochondrial genomes of endangered form of the Sevan trout Salmo ischchan aestivalis are published in this paper. The mitochondrial DNA (mtDNA) is 16,677 base pairs (bp) in length and contained 13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes. The overall base composition of the genome in descending order was 29.4% - C, 27.9% - A, 26.0% - T, 16.7% - G, without a significant AT bias of 53.9%.

Fish introductions in the former Soviet Union: The Sevan trout (Salmo ischchan) - 80 years later.

The Soviet Union played the leading role in fish introductions in Eurasia. However, only 3% of all introductions prior to 1978 gave a commercial benefit. One of the noteworthy examples appears to be the Sevan trout (Salmo ischchan Kessler, 1877)-an endemic salmonid of Lake Sevan in Armenia. This species has been introduced to Kirghizstan, Kazakhstan, and Uzbekistan, however, only the Kirghiz population has persisted in relatively high numbers. In this paper we provide the first extensive molecular study of S. ischchan using samples from the native population from Lake Sevan and three hatcheries in Armenia, as well as from the population introduced to Lake Issyk Kul in Kirghizstan. The Kirghiz population has been isolated since the introductions took place in 1930 and 1936. Our results, based on 11 nuclear microsatellites and a 905 bp fragment of the mitochondrial control region suggest that hatcheries have maintained genetic variability by way of ongoing translocations of individuals from Lake Sevan. Simultaneously, significant Garza-Williamson M-values suggest that bottlenecks could have reduced the genetic variability of the wild populations in the past. This hypothesis is supported by historical data, indicating highly manipulated water-level regulations and poaching as two main factors that dramatically impact fish abundance in the lake. On the other hand, a similar situation has been observed in Kirghizstan, but this population likely rebounded from small population size faster than the other populations examined. The Kirghiz population is significantly genetically differentiated from the other groups and have morphological features and biological attributes not observed in the source population. Genetic data imply that the effective population size in the native population is lower than that found in the introduced population, suggesting that some active protection of the Lake Sevan population may be needed urgently.

Two complete mitochondrial genomes of extinct form of the Sevan trout Salmo ischchan danilewskii.

The mitochondrial genomes from two individuals of the extinct subspecies of the Sevan trout Salmo ischchan danilewskii are published in this paper. The mitochondrial DNA (mtDNA) is 16,665 base pairs (bp) in length and contained 13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes. The overall base composition of the genome in descending order was 27.9% of A, 29.4% of C, 16.7% of G, and 26.0% of T without a significant AT bias of 53.9%.

The influence of ph and waterborne metals on egg fertilization of the blue mussel (Mytilus edulis), the oyster (Crassostrea gigas) and the sea urchin (Paracentrotus lividus).

This study evaluated the combined effect of pH and metals on the egg fertilization process of two estuarine species, the blue mussel (Mytilus edulis), the oyster (Crassostrea gigas) and a marine species, the sea urchin (Paracentrotus lividus). The success of egg fertilization was examined after exposure of gametes to sediment extracts of various degrees of contamination at pH 6.0, 6.5, 7.0, 7.5 and 8.0. At the pH levels from 6.5 to 8.0, the egg fertilization of the different species demonstrated different sensitivity to metal and/or acidic exposure. In all species, the results revealed that egg fertilization was almost completely inhibited at pH 6.0. The egg fertilization of the blue mussel M. edulis was the least sensitive to the exposure while that of the sea urchin P. lividus demonstrated a concentration-dependent response to the pH levels from 6.5 to 8.0. The results of this study revealed that acidity increased the concentration of several metal ions (Cr, Ni, Cu, Zn, Cd, and Pb) but reduced its availability to the organisms, probably related to the reactivity of the ions with most non-metals or to the competition among metals and other waterborne constituents.