The contamination of inland waters by microplastic fibres under different anthropogenic pressure: Preliminary study in Central Europe (Poland).

The contamination of freshwater ecosystems with microfibres has not yet been studied in Poland. We analysed samples from a river and three lakes located in central and northeastern Poland. A significantly higher number of fibres were reported in the river, which runs through large cities, compared with the lake situated within the Landscape Park. Fibres smaller than 1.0 mm dominated, especially in the river where they constituted 39% of all fibres detected. We found more microplastics (⩽ 4930 fibres·m-3) by using a mesh size of 20 µm compared with other studies of inland waters. The use of Raman spectroscopy allowed us to identify conventional plastic polymers: polyethylene terephthalate, polyester and polyurethane. We estimated that up to 25 g of microplastic in the form of fibres might be in the lake water under the surface. We found microplastic fibres in Majcz Lake situated within the Masurian Landscape Park. This suggests that microfibres are carried by the wind and rain and enter freshwater isolated from sewage outlets. By using the control sample and an air-test of microfibres in the laboratory, we observed that there is a high probability of contamination with microplastic in the field samples (up to 30% of all fibres detected). The contamination risk noted from the samples cannot be ignored; this could be particularly important for analysis of microplastic in remote freshwater ecosystems.

Intensity-dependent response to temperature in hydra clones.

The intensity of environmental factors differs in natural habitats and could shape the response of an animal that is able to assess a factor's gradient. However, intensity-dependent response to environmental factors has been only occasionally reported in animals. In laboratory experiments, I studied changes in sexual induction in response to a series of temperature decreases in different clones of Hydra oligactis. The percentage of sexually-induced clone-mates was related to the temperature gradient intensity. This intensity-dependent response was observed independently of the H. oligactis clone and gender. The magnitude of the response differed significantly between the clones originated from the distinct sites. The possible significance of the intensity-dependent response in the Hydra clones is discussed in evolutionary terms.

Epibiont Cohabitation in Freshwater Shrimp Neocaridina davidi with the Description of Two Species New to Science, Cladogonium kumaki sp. nov. and Monodiscus kumaki sp. nov., and Redescription of Scutariella japonica and Holtodrilus truncatus.

This contribution presents the occurrence of epibiotic species associated with Neocaridina davidi shrimp collected in the wild, aquaculture ponds, and aquaria. A total of 900 shrimp are imported from Taiwan, three-quarters of which host at least one of the recorded epibionts. Among those epibionts, two species new to science are discovered, Cladogonium kumaki sp. nov. and Monodiscus kumaki sp. nov., while the other two, Holtodrilus truncatus and Scutariella japonica, are redescribed. The largest number of epibionts is found in shrimp collected from aquaculture ponds and the lowest in individuals from aquaria. Epibiont occurrence differs across designated microhabitats. The epibionts may be introduced alongside their host outside their native range, and their presence may affect shrimp breeding rates. Thus, more control over them should be provided. Their spread can be limited by removal from the host during molting or manually, as well as by using interspecies interactions.

First Evidence of Microplastic Occurrence in the Marine and Freshwater Environments in a Remote Polar Region of the Kola Peninsula and a Correlation with Human Presence.

Microplastics (MPs) have even been detected in remote environments, including high-latitude regions, where human activities are restricted or strongly limited. We investigated the surface water of the bays of the Barents Sea and the freshwater lakes that are located close to and several kilometers from a year-round resident field station in the remote tundra region of the Kola Peninsula. The microplastics' presence in aquatic environments in this region has not been indicated yet. Microplastics were detected in all samples collected from the Barents Sea (<4800 items·m-3) and the lakes (<3900 items·m-3). Fibers made from polyethylene terephthalate (PET)-the most common thermoplastic polymer of the polyester family-and semi-synthetic cellulosic rayon were the most dominant. This indicated that the source of fiber contamination may come from protective clothes, ropes, ship equipment, and fishing nets. Small microplastics can spread through current and atmospheric transport. The Norwegian Current is likely responsible for the lack of correlations found between MP contamination and the distance from the field station between the studied bays of the Barents Sea. On the contrary, a significant correlation with human presence was observed in the concentration of microfibers in the water of the tundra lakes. The number of MP fibers decreased with an increase in the distance from the field station. This is the first study, to the best of our knowledge, that reports such a correlation in a remote region. We also discuss implications for animals. Our results show that even the most isolated ecosystems are not free from microplastic pollution.

Collembola (Hexapoda) as Biological Drivers between Land and Sea.

Macroalgae debris accumulated onshore function as points of interaction between marine and terrestrial ecological systems, but knowledge of the importance of detritivores facilitating the introduction of organic matter via the detritus pathway into neighbouring ecosystems, is still poorly understood. In particular, not much is known about biodiversity patterns and the colonisation of macroalgal debris by terrestrial, detritivorous soil microarthropods in the harsh environmental conditions in the subpolar Arctic region. We hypothesised that (i) soil microarthropods of the coastal tundra, including Collembola, can cross the ecosystem boundary and colonise decaying and freshly exposed macroalgae; and (ii) various inundation regimes by sea water, microhabitat stability and decaying of macroalgae drive distribution patterns of collembolan species. Our results suggest that environmental filtering influences collembolan species' distributions across the examined gradient and induces sorting of species according to their functional traits, including dispersal ability, resistance to disturbance and environmental tolerance.

Phylogenetic Relatedness within the Internally Brooding Sea Anemones from the Arctic-Boreal Region.

Phylogenetic analyses based on mitochondrial 16S rDNA, nuclear 28S rDNA, and morphological and ecological traits of Aulactinia, Urticina and Cribrinopsis sea anemones inhabiting the Arctic-boreal region indicate discordances between trees derived from molecular sequences and those based on morphological traits. Nuclear genes were more informative than mitochondrial and morphological datasets. Our findings indicate that 16S rDNA has limited applicability for phylogenetic analyses at lower taxonomic levels and can only be used for distinction of families. Although 28S rDNA allowed for the classification of distinct genera, it could not confirm that species of Urticina and Cribrinopsis, which appeared to be closely related, were correctly separated into two different genera. The nuclear tree revealed inconsistencies between specimens belonging to European Urticina crassicornis and Pacific U. crassicornis; the latter seems to be a different species. In contrast to Pacific U. crassicornis, the specimens collected from different localities in the Barents Sea are on the same tree branch. The same was observed for specimens of Aulactinia stella. Both species brood their young internally. The dispersal of sea anemones with brooding juveniles seems to be less limited than expected and might be sufficient to settle habitats more than a thousand kilometers away.

Alpha-Linolenic Acid, but Not Palmitic Acid, Negatively Impacts Survival, Asexual Reproductive Rate, and Clonal Offspring Size in Hydra oligactis.

Hydra, as sit-and-wait predators with limited food selectivity, could serve as model organisms for the analysis of the effect of a particular dietary component on growth and reproduction. We investigated the effect of food quality and of diets enriched with palmitic (PAM) or α-linolenic acid (ALA) on the life history traits of two hydra species: Hydra oligactis and Hydra vulgaris. We tested the hypothesis that a diet enriched with polyunsaturated fatty acids (PUFA) can stimulate growth and reproduction in simple metazoans with a sit-and-wait type of predatory strategy. Our results revealed that a diet based on Artemia nauplii, which are not a natural food for freshwater hydra, stimulated growth, asexual reproduction, and survival in hydra. Artemia nauplii were characterized by the highest lipid content of all used food sources. The analysis of the fatty acid content of hydra indicated the domination the n-6 fatty acids over n-3 (eicosapentaenoic acid [EPA], docosahexaenoic acid [DHA], and ALA). Arachidonic acid appeared to be the dominant PUFA in Hydra, irrespective of diet supplementation with palmitic acid or ALA. The dietary supplementation of ALA negatively affected the survival, asexual reproductive rate, and size of clonal offspring of H. oligactis and had no effect on the life history traits of H. vulgaris. Our results also suggest that the hydras are not able to efficiently convert ALA into other essential fatty acids, such as EPA and DHA. To our knowledge, this is the first report about the adverse effects of n-3 fatty acid supplementation in primitive metazoans such as hydra.

Predation effects on the evolution of life-history traits in a clonal oligochaete.

Although size at maturity and size and number of offspring are life-history traits widely studied in sexual and parthenogenetic reproduction, there is no such research on animals reproducing asexually without the involvement of gametes. Here we present an individual-based model in combination with experiments to study the clonal growth of Stylaria lacustris, an oligochaete reproducing through fission. We studied the effect of individual size at fission and fission ratio on clone fitness. Our results show that in benign environments without predators, fitness is higher when small worms produce small offspring. Then we included size-specific sublethal predation and found that the fitness of the clone is maximized when parental worms start fission at a large size and produce large descendants intercalated in the middle of the parental worm's body. These results agree with empirical findings. Furthermore, the results of our own laboratory experiment revealed that when S. lacustris is exposed to chemical alarm signals from injured conspecifics, it alters its life history in the same direction as predicted by the model. Our findings suggest that the effect of size-specific sublethal predation is similar to the effect of size-specific lethal predation because both modes of predation result in size-dependent prey mortality.