26 September 2022

Faiad, 2022

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Faiad S. 2022. Under what conditions can a novel invader (the marbled crayfish, Procambarus fallax f. virginalis) exert predation pressure on schistosome-competent snails? Master's thesis, School of Aquatic and Fisheries Sciences, University of Washington. http://hdl.handle.net/1773/49377




The human burden of environmentally transmitted infectious diseases can depend strongly on ecosystem factors, including the presence or absence of natural enemies. Like natural enemies, non-native species influence the abundance and distribution of their prey and competitors, yet the impact of these invaders on the transmission of diseases remains largely unexplored. One environmentally transmitted infectious disease with potential to be influenced by natural enemies is schistosomiasis, a parasitic disease infecting over 200 million people across South America, Asia, and Africa. The marbled crayfish (Procambarus fallax f. virginalis) first appeared in Madagascar in 2005 and quickly spread across the country, overlapping with the distribution of freshwater snails that serve as the intermediate host of Schistosoma spp. worms. Marbled crayfish can tolerate a wide range of ecological conditions, colonize diverse habitats, and may serve as an enemy of schistosome-competent snails in areas where natural predators cannot–something that is urgently needed in a country where schistosomiasis prevalence in some villages can range up to 94%. Here, I experimentally assessed marbled crayfish consumption of uninfected and infected schistosome-competent snails (Biomphalaria glabrata and Bulinus truncatus) across a range of temperatures, reflective of the habitat range of the marbled crayfish in Madagascar. Crayfish consumption was significantly influenced by crayfish weight, as well as the interaction between weight and temperature. Compared to small crayfish, large crayfish experienced a greater increase in consumption at moderate temperatures (25 and 30°C) relative to extreme temperatures (15, 20, and 35 °C). The temperature at which the rate of consumption was highest (i.e., the thermal optimum) was estimated to be 31.1 °C for small crayfish (<3.90 g), 27.7 °C for medium crayfish (3.91 – 6.62 g), and 28.7 °C for large crayfish (> 6.3 g). Neither snail species nor snail infection status were significantly associated with consumption. My results suggest that ecological parameters, such as temperature and crayfish weight, influence rates of consumption and, in turn, the potential regulatory impact of the marbled crayfish on snail host populations.

20 September 2022

Brown and Therriault 2022

Canadian Journal of Fisheries and Aquatic Sciences cover

Brown NEM, Therriault TW. 2022. The hidden risk of keystone invaders in Canada: a case study using non-indigenous crayfish. Canadian Journal of Fisheries and Aquatic Sciences 79(9): 1479-1496. https://doi.org/10.1139/cjfas-2021-0245



Invasive species have long been recognized as a serious threat to freshwater ecosystems. This is especially true for invasive species in keystone positions in food webs that can cause major disruption and can lead to unexpected outcomes. Crayfish occupy a central trophic position and non-indigenous crayfish have been shown to substantially disrupt ecosystems they invade. Here, we assess eight non-indigenous crayfish to 21 freshwater ecoregions in Canada using a screening-level risk assessment. We found that ecoregions in Canada that were warmer and contained high native freshwater diversity were most at risk from crayfish invasions, particularly: the Laurentian Great Lakes, St. Lawrence, English-Winnipeg Lakes and Coastal British Columbia ecoregions. Four crayfish species consistently had higher scores: rusty (Faxonius rusticus), virile (Faxonius virilis), signal (Pacifastacus leniusculus), and red swamp (Procambarus clarkii). Of these high-risk crayfish, only the red swamp crayfish is not yet established in Canada but is present in US waters of the transboundary Great Lakes ecoregion. Our study is the first to evaluate the relative risks that non-indigenous crayfish pose to freshwater ecosystems in Canada.


Keywords: None provided.

Bláha and colleagues 2022

Environmental Monitoring and Assessment cover

Bláha M, Weiperth A, Patoka J, Szajbert B, Balogh ER, Staszny Á, Ferincz Á, Lente V, Maciaszek R, Kouba A. 2022. The pet trade as a source of non-native decapods: the case of crayfish and shrimps in a thermal waterbody in Hungary. Environmental Monitoring and Assessment 194(10): 795. https://doi-org.libaccess.lib.mcmaster.ca/10.1007/s10661-022-10361-9


Ornamental aquaculture and the related pet industry are known to be important sources of non-native species worldwide. In the temperate zone, thermal waterbodies are attractive places for irresponsible owners to release unwanted freshwater pets including decapod crustaceans. Several non-native ornamental species have been reported in the thermal locality of Miskolctapolca (a suburb of Miskolc, Hungary). So we surveyed this site in March 2019–November 2021 to update local occurrence records and detect potentially newly released species. A well-established population of Neocaridina denticulata and the occurrence of Caridina cf. babaulti had previously been noted. However, for the first time at this site, we found the shrimps Atyopsis moluccensis, Caridina gracilirostris and C. multidentata, as well as the crayfish Procambarus virginalis, P. clarkii, Cherax quadricarinatus, C. boesemani and C. snowden, and several formally undescribed Cherax species originating from New Guinea. Furthermore, in most species, gravid females carrying eggs were also noticed. Three shrimps, A. moluccensis, C. gracilirostris and C. multidentata, were recorded for the first time in European wild. Further monitoring of this locality and better education of the general public regarding the risks associated with the release of non-native species are strongly recommended.


Keywords: Ornamental species • invasive species • Decapoda • Europe • thermal water

24 August 2022

Boštjančić and colleagues 2022

BMC (BioMed Central) logo
Boštjančić LL, Francesconi C, Rutz C, Hoffbeck L, Poidevin L, Kress A, Jussila J, Makkonen J, Feldmeyer B, Bálint M, Schwenk K, Lecompte O, Theissinger K. 2022. Host-pathogen coevolution drives innate immune response to Aphanomyces astaci infection in freshwater crayfish: transcriptomic evidence. BMC Genomics 23(1): 600. https://doi.org/10.1186/s12864-022-08571-z




For over a century, scientists have studied host-pathogen interactions between the crayfish plague disease agent Aphanomyces astaci and freshwater crayfish. It has been hypothesised that North American crayfish hosts are disease-resistant due to the long-lasting coevolution with the pathogen. Similarly, the increasing number of latent infections reported in the historically sensitive European crayfish hosts seems to indicate that similar coevolutionary processes are occurring between European crayfish and A. astaci. Our current understanding of these host-pathogen interactions is largely focused on the innate immunity processes in the crayfish haemolymph and cuticle, but the molecular basis of the observed disease-resistance and susceptibility remain unclear. To understand how coevolution is shaping the host’s molecular response to the pathogen, susceptible native European noble crayfish and invasive disease-resistant marbled crayfish were challenged with two A. astaci strains of different origin: a haplogroup A strain (introduced to Europe at least 50 years ago, low virulence) and a haplogroup B strain (signal crayfish in lake Tahoe, USA, high virulence). Here, we compare the gene expression profiles of the hepatopancreas, an integrated organ of crayfish immunity and metabolism. 




We characterised several novel innate immune-related gene groups in both crayfish species. Across all challenge groups, we detected 412 differentially expressed genes (DEGs) in the noble crayfish, and 257 DEGs in the marbled crayfish. In the noble crayfish, a clear immune response was detected to the haplogroup B strain, but not to the haplogroup A strain. In contrast, in the marbled crayfish we detected an immune response to the haplogroup A strain, but not to the haplogroup B strain.




We highlight the hepatopancreas as an important hub for the synthesis of immune molecules in the response to A. astaci. A clear distinction between the innate immune response in the marbled crayfish and the noble crayfish is the capability of the marbled crayfish to mobilise a higher variety of innate immune response effectors. With this study we outline that the type and strength of the host immune response to the pathogen is strongly influenced by the coevolutionary history of the crayfish with specific A. astaci strains.

Open access

22 July 2022

Maciaszek and colleagues 2022

European Zoological Journal cover

Maciaszek R, Jabłońska A, Prati S, Wróblewski P, Gruszczyńska J, Świderek W. 2022. Marbled crayfish Procambarus virginalis invades a nature reserve: how to stop further introductions? The European Zoological Journal 89(1): 888-901. https://doi.org/10.1080/24750263.2022.2095046



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.


Keywords: alien species • freshwater crustacean • ornamental pet trade • inland waters • Central Europe


Open access


18 July 2022

Mojžišová and colleagues 2022

Mojžišová M, Svobodová J, Kozubíková-Balcarová E, Štruncová E, Stift R, Bílý M, Kouba A, Petrusek A. 2022. Long-term changes in the prevalence of the crayfish plague pathogen and its genotyping in invasive crayfish species in Czechia. NeoBiota 74: 105–127. https://doi.org/10.3897/neobiota.74.79087



The widespread presence of North American alien crayfish in Europe is a major driver of native crayfish population declines, mainly because they are chronic carriers of the oomycete Aphanomyces astaci responsible for crayfish plague. Screening for the crayfish plague pathogen in host populations has become a common practice across Europe, but sampling usually covers spatial but not temporal variation. Our study focuses on the current situation in Czechia, where screening for A. astaci was first conducted in the mid-2000s. We provide data about the distribution and prevalence of this pathogen at almost 50 sites with three host crayfish: the spiny-cheek crayfish Faxonius limosus, signal crayfish Pacifastacus leniusculus, and marbled crayfish Procambarus virginalis. Among these sites were 20 localities that were resampled several years (usually more than a decade) after the original screening for A. astaci. We did not detect any A. astaci infection in two studied P. virginalis populations but documented several new hotspots of highly infected P. leniusculus in Czechia, and the first site with the coexistence of the latter with F. limosus. Our data suggest that despite some fluctuations, A. astaci prevalence in North American host populations generally does not tend to change significantly over time; we only observed two cases of a significant increase and one of a significant decrease. We no longer detected A. astaci in several originally weakly infected populations, but our data suggest it likely still persists in these areas and threatens native crayfish populations. At the single known site in the country where P. leniusculus and F. limosus coexist, we documented the presence of the same A. astaci genotype group in both crayfish species, likely due to interspecific transmission of the pathogen from the former host to the latter. However, genotyping of A. astaci in infected host individuals still supported the link between specific pathogen genotypes and crayfish hosts, suggesting that assessment of sources of mass mortalities from the pathogen genotyping is feasible in European regions where the mutual contact of different American crayfish species is uncommon.

Keywords: Aphanomyces astaci • infection prevalence • interspecific pathogen transmission • invasive crayfish distribution • microsatellite genotyping • mitochondrial haplogroups • qPCR genotyping

23 June 2022

Tresnakova and colleagues 2022

Logo for journal "Biology"

Tresnakova N, Kubec J, Stara A, Zuskova E, Faggio C, Kouba A, Velisek J. 2022. Chronic toxicity of primary metabolites of chloroacetamide and glyphosate to early life stages of marbled crayfish Procambarus virginalis. Biology 11: 927. https://www.mdpi.com/2079-7737/11/6/927




Degradation products of herbicides, alone and in combination, may affect non-target aquatic organisms via leaching or runoff from the soil. The effects of 50-day exposure of primary metabolites of chloroacetamide herbicide, acetochlor ESA (AE; 4 µg/L), and glyphosate, aminomethylphosphonic acid (AMPA; 4 µg/L), and their combination (AMPA + AE; 4 + 4 µg/L) on mortality, growth, oxidative stress, antioxidant response, behaviour, and gill histology of early life stages of marbled crayfish (Procambarus virginalis) were investigated. While no treatment effects were observed on cumulative mortality or early ontogeny, growth was significantly lower in all exposed groups compared with the control group. Significant superoxide dismutase activity was observed in exposure groups, and significantly higher glutathione S-transferase activity only in the AMPA + AE group. The gill epithelium in AMPA + AE-exposed crayfish showed swelling as well as numerous unidentified fragments in interlamellar space. Velocity and distance moved in crayfish exposed to metabolites did not differ from controls, but increased activity was observed in the AMPA and AE groups. The study reveals the potential risks of glyphosate and acetochlor herbicide usage through their primary metabolites in the early life stages of marbled crayfish.  


Open access