This contribution presents new observations of the red swamp crayfish,Procambarus clarkiiin Poland. The species was detected in Żerań Canal and Krasiński Garden in Warsaw (central Poland) where 5 and 2 individuals were collected respectively as well as in Dąbie Pond in Krakow (southern Poland) with total of 4 crayfish observed. These new sites are located approximately 500 km eastward (Warsaw) and 240–260 km northward (Krakow) from the nearest European sites where this species has been previously recognised (near Berlin, Germany, Egerszalók and Budapest, Hungary), thus are the furthest north-east records of the species in European open waters. It is likely that the examined stock originates from single introductions, however, presence of the juveniles caught in Warsaw suggests that the population found there may be breeding. The findings are discussed with available literature describing possible waysP. clarkiimay use to colonize new habitats as well as the impact it has on the invaded ecosystems in general and native crayfish in particular.

In the European Union, aquarium pets are organisms intended for closed places (e.g., pet shops, garden ponds, home aquariums). Until April 2021, regulations did not require veterinary inspection of these animals within the EU, although there is a potential risk of such organisms being released into the environment along with their symbiotes or parasites. Currently, a “disease-free” declaration is required, but no aquarium snail pathogen that needs attention in international trade has been included in the list of potential hazards. Here, we intended to check whether molluscs from the pet trade could be a source of parasites. We answered this question by using Anentome helena, a popular commodity in the ornamental pet industry, as a research model. Snail specimens were randomly collected from aquarium pet stocks imported from Bangkok (Thailand) to Warsaw (Poland) in March 2020. In total, three specimens were subjected to histological examination and 27 specimens were autopsied. Histological analysis revealed that one snail was infected with rediae (and the cercariae inside them). Our study is the first to show the presence of digenean larvae in A. helena originating from the ornamental pet industry. The spread of such “hitchhikers” in non-native areas will likely be associated with threats to environmental and public health. Therefore, it is necessary to constantly draw public attention to the possible consequences of releasing ornamental pets into the non-native environment.

The release of ornamental pets and associated pathogens outside their native range might directly or indirectly impact the recipient community. In temperate regions, e.g., central Europe, feral freshwater species of tropical and sub-tropical origins are mainly constrained to thermally polluted waters and thermal springs. However, species with high environmental plasticity and reproduction rates, such as the shrimp Neocaridina davidi, may adapt to colder water regimes over time. A widening thermal niche may eventually overcome thermal barriers, further expanding the range and enhancing transmission opportunities for host generalist parasites. This study assesses the observed (field observations) and theoretical (species distribution models) range expansion of N. davidi and associated parasites in Europe. We report three newly established N. davidi populations from thermally polluted waters in central Europe (Germany, Hungary, and Slovakia) and provide further evidence of its range expansion into colder environments. Species distribution models predict thermally suitable habitats in the Mediterranean and a foreseeable expansion into Western Europe and the Balkans by 2050. We confirm the presence of the microsporidian parasite Ecytonucleospora hepatopenaei in feral N. davidi populations across Europe and expand the list of microsporidians found in this host from two to four. Furthermore, we provide the first evidence of parasite spillover from/to the invasive crayfish Procambarus clarkii, suggesting that parasite exchange with native biota might be possible. Such possibility, coupled with an ongoing range expansion of N. davidi bolstered by human-mediated introductions and climate change, will likely exacerbate the impact on native biota.

We hereby provide the first documented data on the occurrence of a viable Procambarus virginalis population in a nature reserve in Poland and the steps that were taken to prevent further introductions of the species in the country. To date, Poland represents the most north-eastward distribution area in Europe, where the species occurs in ecosystems with natural water temperature regimes. The ecological plasticity of P. virginalis and its obligate parthenogenetic reproduction make this crayfish an exceptional invader. The crayfish may have detrimental effects on the native invertebrates, amphibians, and fish, and alter the state of the entire ecosystem. Therefore, we investigated the presence of the species in the nature reserve of Pojezierze Łęczyńskie Landscape Park after a suspected P. virginalis individual was found by a local citizen. The nature reserve also includes an area designated to protect native amphibians and turtles. Our study revealed the presence of a thriving population of P. virginalis in the protected area and clear indications of its impact on native and invasive species, both in aquatic and terrestrial environments. If no action is taken, the species will likely expand to other water bodies across the country. An extensive sensibilization campaign allowed us to find additional invaded areas and significantly contribute to the effective ban of this and other invasive crayfish species from private and commercial online trade. Raising public awareness and banning invasive crayfish species trade is essential for successfully detecting and preventing further introductions.

This contribution presents the first record of ornamental shrimp epibiont, Scutariella japonica (Platyhelminthes: Temnocephalida) in European waters. The species lives on freshwater Atyidae shrimp from temperate, subtropical and tropical zones of South-East Asia. In total, 120 individuals of Neocaridina davidi shrimp were caught in thermally polluted canal of Oder river, near the city of Gryfino, in the northwest part of Poland. In that group, 5.83% were infected with scutariellids. Among shrimp, females were mostly infected (85.71%). Since ornamental shrimp released into thermally polluted water bodies have been also noticed in surrounding waters of natural temperature regime in Europe, S. japonica may spread further following potential expansion of the Neocaridina shrimp in Oder river. It is possible that other crustaceans, both native and alien which are present at this location, may also become vectors of this epibiont.