The first observation of the presence of microplastics in wild common bleak (Alburnus alburnus L.) and standardization of extraction protocols

The presence of microplastics (MPs) in the gastrointestinal tract, muscle, and whole-body samples of common bleak Alburnus alburnus L. from Gruža Reservoir (Central Serbia) was studied for the first time. Different protocols for MPs extraction were applied to determine the most efficient one. The study aimed to modify existing protocols to be cost-effective, efficient in digestion, and with no detrimental effect on potentially present MPs polymers. In this study, the digestion with 10% KOH during 48 h at 40°C was efficient for the gastrointestinal tract and muscle. Digestion with 10% KOH during 72 h at 40°C was the most efficient for whole-body samples. The usage of NaClO proved successful in digestion of the gastrointestinal tract overnight at room temperature. Fibers detected in the samples are assumed to be of plastic origin. The general goal was to establish a protocol for extracting MPs from fish tissue in wild populations to obtain results and determine the degree of pollution.Publishe

Assessment Of Genotoxic Potential Of The Velika Morava River Basin

The Danube River is highly affected by human activity. Wastewaters discharging into the Danube River stream are one of the major problems, especially at Croatia-Serbia river section. The Velika Morava River is the greatest Serbian river and a significant tributary of the Danube River. Consequently, the water quality of the Velika Morava River could have a great impact on the water quality of the Danube River. In this study, the level of genotoxic potential along the Velika Morava River Basin was evaluated by using a battery of in vitro and in situ bioassays. Within the in vitro approach, SOS/umuC test on Salmonella thyphimurium TA1535/pSK1002 and the comet assay on HepG2 cell line were employed for genotoxicity testing of native water samples. The level of DNA damage on erythrocytes of bleak specimens (Alburnus alburnus) was observed using the alkaline and Fpg modified comet and micronucleus assays within in situ testing. The concentration of toxic metals in fish tissues and physico-chemical water status were chosen as parameters of pollution pressure on selected sites. Obtained results indicated lower sensitivity of selected in vitro tests when compared to in situ. Also, the tests using the in situ approach showed a range of sensitivity. Namely, the alkaline comet assay showed a greater potential than Fpg modified comet test and micronucleus assay in distinguishing between sites. According to results, application of complex bioassays battery was shown as a better choice in eco/genotoxicological studies than using only one bioassay. In that way, a holistic approach is appropriate for this type of study

Population Characteristics of Spirlin <i>Alburnoides bipunctatus</i> (Bloch, 1782) in Serbia (Central Balkans): Implications for Conservation

The aim of this study was to evaluate the population characteristics of spirlin, Alburnoides bipunctatus, in Serbia, since this small fish species is facing a severe decline in its abundance and its natural habitats in Europe. We investigated the spirlin population dynamics, including size, age structure, growth pattern, mortality, and exploitation rate. Additionally, we used the Uniform Manifold Approximation and Projection approach with the Decision Tree algorithm to investigate the influence of different environmental parameters on the population parameters to unveil which factors shape the abundance and distribution of spirlin. The results showed that the highest values of production, abundance, and biomass were estimated in sites with low temperature, optimal pH, and well-oxygenated water, even though we found them in heavily polluted waters with extremely high values of conductivity. Moreover, we observed a pattern of migratory behavior, in which spirlin migrate upstream to sites at a higher altitude in early summer and autumn. Despite the putative vulnerability and high sensitivity of spirlin populations, our results showed that the species was abundant, occurring in altered habitats (due to pollution, climate change, anthropogenic pressure, etc.)

Cryopreservation of Danube barbel Barbus balcanicus sperm and its effects on sperm subpopulation structure

© 2020. by the Serbian Biological Society. The objective of this study was to develop a successful freezing protocol for cryopreservation of Danube barbel sperm, and to identify the presence of different spermatozoa subpopulations. By testing different concentrations of different cryoprotectants, we determined that the use of 5% dimethyl sulfoxide (DMSO) yielded the highest total motility of ∼25%. Cooling rates influenced by frame height and cooling time in liquid nitrogen vapor showed that a frame height of 3 cm and cooling time of 2 min yielded the highest post-thaw motility. Supplementation of cryomedia with 0.1 M of sugars led to an increase in the total post-thaw motility by ∼50%, while protein supplementation lowered post-thaw motility. Motile spermatozoa hierarchically clustered according to their motility parameters, displaying a four-subpopulation (SP1-SP4) structure. SP1 was defined by low values of velocity but high overall linearity; SP2 was comprised of fast non-linear spermatozoa, that had high velocity values but low linearity; SP3 was characterized by fast linear spermatozoa, and SP4 by slow non-linear spermatozoa. Protocols developed in this study will lead to the creation of new and enhanced conservation strategies for this species

Diet seasonality and food overlap of Perca fluviatilis (Actinopterygii: Perciformes: Percidae) and Rutilus rutilus (Actinopterygii: Cypriniformes: Cyprinidae) juveniles: A case study on Bovan Reservoir, Serbia

European perch, Perca fluviatilis Linnaeus, 1758 and roach, Rutilus rutilus (Linnaeus, 1758) are the most common species present in mesotrophic and eutrophic lakes throughout Europe. Their biomass, especially in juvenile stages, contributes the most to the fish production of these ecosystems. In Bovan Reservoir, these two species constitute the bulk of the juvenile fish biomass. This study aimed to investigate the feeding composition of these two species in order to evaluate their niche overlap due to the availability of resources during different seasons. Traditional diet analysis indices and Kohonen artificial neural network (i.e., a self-organizing map, SOM) were used to investigate the diet of 158 individuals of both species and evaluate their food niche overlap. The indicator value (IndVal) was applied to identify indicator food categories based on which the contents of their alimentary tracts were grouped first into neurons and then into clusters on the SOM. Our results showed that juvenile fish used zooplankton and benthic prey in their diet. Roach often fed on nonanimal prey, while perch of age 0+ used fishes in the diet. Additionally, four clusters of neurons were isolated on the SOM output network. The distribution of perch and roach alimentary tracts in neurons indicated no high degree of competition between them. While diet analyses indices show which food category is generally important in specimensʼ diet, the SOM recognizes those specimens and arranges them together into the same or adjacent neurons based on dominant prey. Understanding fish feeding habits is critical for the development of conservation and management plans. Since Bovan is a eutrophic reservoir, our knowledge of fish feeding habits needs to be considered for stocking strategies in the future