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


15 June 2022

SyFy article spreading the word

There’s been an uptick in my Google Alerts because of a new article about Marmorkrebs on SyFy Wire.


At first, I though the article was recycled from the big burst of coverage when the marbled crayfish genome was sequenced. A good chunk of the article discusses the 2018 paper, and it uses a press photo that came out at that time.


But as I saw back in 2018, when one popular news site does a story, many more will pick it up.


Update, 6 July 2022: Ths story got picked up on Yahoo! News. Good time for me to talk about the misleading title.


The title - “Cloned crayfish accidentally created in an aquarium are conquering the world” suggests people were actively mucking about with crayfish to accomplish something. No evidence of that.


There is zero evidence marbled crayfish were “created” in an aquarium. Again, it suggests human involvement when there was almost certainly none. Triploid (but maybe not reproductive) individuals of the sexual ancestor exist in wild. Early Marmorkrebs may have been collected from the wild and only later got a foothold in the aquarium trade, 


External links


Cloned crayfish accidentally created in an aquarium are conquering the world

01 June 2022

Marn and colleagues 2022

Conservation Physiology cover

Marn N, Hudina S, Haberle I, Dobrović A, Klanjšček T. 2022. Physiological performance of native and invasive crayfish species in a changing environment: insights from Dynamic Energy Budget models. Conservation Physiology 10(1): coac031. https://doi.org/10.1093/conphys/coac031



Crayfish are keystone species important for maintaining healthy freshwater ecosystems. Crayfish species native to Europe, such as Astacus astacus and Austropotamobius torrentium, are facing decline and are increasingly endangered by changing climate and invasions of non-native crayfish, such as Pacifastacus leniusculus and Procambarus virginalis. The success of these invasions largely depends on differences in ontogeny between the native species and the invaders and how changes in the environment will affect the ontogeny. Dynamic Energy Budget (DEB) models can be used to investigate such differences because the models capture dependence of metabolism, and therefore ontogeny, on environmental conditions. We develop DEB models for all four species and investigate key elements of ontogeny and metabolism affecting interspecific competition. We then use the DEB models to predict individual growth and reproduction in current and new conditions that are expected to arise from climate change. Although observations suggest that P. leniusculus poses the major threat to native species, our analysis identifies P. virginalis, in spite of its smaller size, as the superior competitor by a large margin—at least when considering metabolism and ontogeny. Our simulations show that climate change is set to increase the competitive edge of P. virginalis even further. Given the prospects of P. virginalis dominance, especially when considering that it is able to withstand and spread at least some crayfish plague strains that severely affect native species, additional research into P. virginalis is necessary.


Open access


13 May 2022

Convicted by crayfish

Super quick because I’m in the middle of something, but I have to share this new story of a woman convicted of selling marbled crayfish in the United States.



Update, 18 May 2022: I never, ever, thought I would see the day when Marmorkrebs would be mentioned in a US Department of Justice press release. The press release contains more details of the scale of the operation.

Between August 2020 and June 2021, (Alison) Spaulding sold marbled crayfish in 96 different transactions to buyers in 36 states for approximately $2,812.

According to The Guardian article linked above, Spaulding faces “faces a maximum penalty of a year in prison and up to $100,000 in fines, although a federal judge is set to consider a lesser penalty under a plea deal.”

19 April 2022

Bohman and colleagues 2022

Crayfish News

Bohman P, Edsman L, Mrugała A. 2022. Is this a Swedish signal crayfish or an alien marbled crayfish? Crayfish News 44(1): 1, 3-6. https://pub.epsilon.slu.se/27549/1/bohman-p-et-al-220414.pdf




Without abstract. Edited excerpt:


Marble-coloured signal crayfish may superficially look similar to another non-native crayfish species, the Marmorkrebs (the marbled crayfish, Procambarus virginalis), and may therefore be incorrectly identified as that species. Both crayfish species are on the European Union’s list of invasive alien species of Union’s concern (EU regulation 1143/2014) and thus highly unwanted in Sweden. The first illegally introduced Marmorkrebs in natural waters in Sweden was found in 2012. During 2013, several additional marble-coloured morphs of juvenile signal crayfish were discovered in Sweden. Therefore, to properly manage invasive alien species and to take correct and swift mitigation actions, it is imperative to have tools for quick and unambiguous species identification.