Survival of Embryos and Fry of Sea Trout (Salmo trutta m. trutta) Growing from Eggs Exposed to Different Concentrations of Selenium during Egg Swelling.

Adequate selenium (Se) availability enhances the health and growth of organisms, but overdose of it can be harmful and pathogenic. The study's objective was to analyse the impact of short-term exposure of sea trout fertilised eggs to inorganic selenium (SeO2) at concentrations from 0 to 32 mg Se L-1 to find the optimal and toxic dose of Se on early fish development. Se accumulated in the body, embryos' survival rate, and growth in the first four months of life was examined. Swelling of fertilised eggs in water supplemented with Se at a concentration from 0.5 to 8 mg Se L-1 was associated with a slightly positive impact on the hatching rate. At higher Se concentration, a harmful effect on the survival of the embryo was observed. The survival of fry was similar in all groups, while the fry length and weight correlated positively with Se concentration in its body. Immersion of fertilised eggs in water enriched with Se during egg swelling can constitute a method to supplement the element to non-feeding stages of fish. In selenium-poor areas, this innovative method can be implemented in aquaculture to improve breeding outcomes. Se concentration should be adjusted to the chemical compound, fish species, and Se's content in the yolk.

Reproductive Potential of Stone Moroko (Pseudorasbora parva, Temminck et Schlegel, 1846) (Teleostei: Cypriniformes: Gobionidae) Inhabiting Central Europe.

Similar to other invasive species, stone moroko is extending its global distribution. The present study aimed to assess the reproductive potential of stone moroko fish in a new habitat in Poland based on analysing the sexual cycle and fecundity. Fish morphometric data, age, and gonadal structures were analysed. Fish age ranged from 0+ to 5+ years. Most females and males (93% and 60%, respectively) had reached sexual maturity in the first year of their life, with the smallest length of 25 mm and 28 mm, respectively. The mean, standard length of the body was 50 mm. The spawning season was spread over four months from late-April to mid-August. Females laid eggs in portions, and the absolute and relative fecundity was 1372 and 1691, respectively. Stone moroko males were ready to spawn for a longer time period than females. The present study shows greater reproductive potential of stone moroko population in the central Europe than the native population, suggesting its successful colonisation in the new habitat.

Detection of Tick-Borne Pathogens of the Genera Rickettsia, Anaplasma and Francisella in Ixodes ricinus Ticks in Pomerania (Poland).

Tick-borne pathogens are an important medical and veterinary issue worldwide. Environmental monitoring in relation to not only climate change but also globalization is currently essential. The present study aimed to detect tick-borne pathogens of the genera Anaplasma, Rickettsia and Francisella in Ixodes ricinus ticks collected from the natural environment, i.e., recreational areas and pastures used for livestock grazing. A total of 1619 specimens of I. ricinus were collected, including ticks of all life stages (adults, nymphs and larvae). The study was performed using the PCR technique. Diagnostic gene fragments msp2 for Anaplasma, gltA for Rickettsia and tul4 for Francisella were amplified. No Francisella spp. DNA was detected in I. ricinus. DNA of A. phagocytophilum was detected in 0.54% of ticks and Rickettsia spp. in 3.69%. Nucleotide sequence analysis revealed that only one species of Rickettsia, R. helvetica, was present in the studied tick population. The present results are a part of a large-scale analysis aimed at monitoring the level of tick infestation in Northwest Poland.

Magnetotactic Bacteria and Magnetosomes as Smart Drug Delivery Systems: A New Weapon on the Battlefield with Cancer?

An important direction of research in increasing the effectiveness of cancer therapies is the design of effective drug distribution systems in the body. The development of the new strategies is primarily aimed at improving the stability of the drug after administration and increasing the precision of drug delivery to the destination. Due to the characteristic features of cancer cells, distributing chemotherapeutics exactly to the microenvironment of the tumor while sparing the healthy tissues is an important issue here. One of the promising solutions that would meet the above requirements is the use of Magnetotactic bacteria (MTBs) and their organelles, called magnetosomes (BMs). MTBs are commonly found in water reservoirs, and BMs that contain ferromagnetic crystals condition the magnetotaxis of these microorganisms. The presented work is a review of the current state of knowledge on the potential use of MTBs and BMs as nanocarriers in the therapy of cancer. The growing amount of literature data indicates that MTBs and BMs may be used as natural nanocarriers for chemotherapeutics, such as classic anti-cancer drugs, antibodies, vaccine DNA, and siRNA. Their use as transporters increases the stability of chemotherapeutics and allows the transfer of individual ligands or their combinations precisely to cancerous tumors, which, in turn, enables the drugs to reach molecular targets more effectively.

Insights into the morphology and molecular characterisation of glacial relict Eurytemoralacustris (Poppe, 1887) (Crustacea, Copepoda, Calanoida, Temoridae).

Eurytemoralacustris (Poppe, 1887) is a stenothermic glacial relict whose narrow environmental requirements make it an indicator species for good ecological conditions. The primary threats to this species are eutrophication and global warming. Many authors have described E.lacustris in taxonomic keys; however, its morphological description is unsatisfactory. Therefore, in this study, we aimed to review morphological characteristics of E.lacustris that were previously undescribed in the literature and to provide the molecular characteristics based on the two conservative mitochondrial genes: cytochrome c oxidase I (COI) and cytochrome b (cytb). The new record of E.lacustris indicates that it is a more widespread species than previously hypothesized. Width-to-length ratio of the last female endopod segment of legs indicates variation among the widely distributed species of the genus in Europe (i.e., E.lacustris, E.velox (Lilljeborg, 1853), and E.affinis (Poppe, 1880)). We also found variability of number of setae on the second segment of male endopod. Furthermore, our analysis confirms the occurrence of species in different than exclusively freshwater habitats.

Genetic Variation in the ND1 Gene and D-loop in Protected and Commercially Exploited European Cisco (Coregonus albula L.) Populations.

The European cisco (Coregonus albula L.) is a species with high environmental requirements. The deterioration of environmental conditions in recent decades has decreased its distribution. Currently the species is conserved by stocking, and the few existing natural populations are at risk of extinction. Therefore, contemporary studies involve not only reporting phenotypic parameters, but also determining the genetic structure of the population. This is an important aspect monitored in the C. albula population, which provides information valuable for proper fishing economy. This study included valuable populations from lakes located in Drawa National Park (DNP) and Wigry National Park (WNP), as well as lakes used for commercial fishing. In order to molecularly characterize the European cisco, the control region and NDl gene were sequenced from 48 individuals from 9 populations from lakes throughout northern Poland. Analysis revealed that populations from two park lakes (Marta, Ostrowieckie) are unique. This was also the case for some sequences originating from Lake Wigry. The mean value of genetic diversity was 0.2% within each region and 0.1-0.3% between the investigated regions. The obtained results demonstrated the necessity to strengthen and protect natural populations of the European cisco, which constitute a valuable element of the European ichthyofauna.

Annual Developmental Cycle of Gonads of European Perch Females (Perca fluviatilis L.) from Natural Sites and a Canal Carrying Post-cooling Water from the Dolna Odra Power Plant (NW Poland).

The European perch is a species endowed with high adaptation capabilities as regards different environmental conditions. The aim of the study was to analyse the annual developmental cycle of ovaries of the European perch from the Oder river, Lake Dabie and a drainage canal (Warm Canal) carrying post-cooling water from the Dolna Odra power plant (annual average water temperature in the canal is higher by 6-8°C than the water of the other sampling sites). Most of the female perch caught in the canal carrying post-cooling water had immature stage 2 gonads (delayed development of the gonads) and were smaller than the fish from the other sites. No traces of spawning in the form of deposed egg strings were found in the drainage canal. Adult individuals avoid high temperatures found in the Warm Canal. In April, in perch from all sites, ovaries with post-spawning oocytes were observed. The spawning season of the females lasted from the beginning of April until May. Stage 4 of gonad development, with oocytes in advanced vitellogenesis, was the longest and ranged from September through February.

Genetic Variation of Salmo trutta L. Populations from the Catchment Areas of the Rega, Parseta and Wieprza Rivers Evaluated by RAPD and SSR Markers.

By using simple sequence repeats (SSR) and random amplification of polymorphic DNA (RAPD) markers, the genetic variability of three Salmo trutta L. populations from three rivers, the Wieprza, the Rega and the Parseta, was determined. The investigated populations showed a high level of genetic variability. Microsatellites showed that observed heterozygosity (Ho) was higher than the expected heterozygosity (He), with most heterozygotes found in the population from the Parseta river and the fewest in the Wieprza population. The F(IS) coefficient in all investigated populations of the sea trout indicate a high excess of heterozygotes. The highest genetic differentiation was observed between the sea trout from the Rega river and those from the Wieprza (0.366). The obtained results based on microsatellite and RAPD analysis showed that the investigated populations formed two groups. The first group consisted of the sea trout populations from the Wieprza and the Parseta rives, while the second group was formed solely by the Rega river population.