31 December 2022

2022 was a slow year for Marmorkrebs research

 This is usually a more optimistic exercise for me.

Graph of publications about Marmorkrebs from 2003 to 2022, with peak in 2018.

After years of being able to write that “This was the best year ever,” the last five years show a downward trend in the number of research publications on Marmorkrebs. This graph shows only journal articles, and excludes one interesting article in Crayfish News. Still, even if I included that, this is the least active year in 6 or 7 years.

This may be because some of the original research questions about Marmorkrebs – their origin and basic biology – are now resolved. It may also be that because this species is more widespread, new records of introductions are less likely to be reported or published.

The biggest story this year was the expanding use of local legislation to ban or regulate the sale of Marmorkrebs in the pet trade. Someone was actually charged under a law for selling Marmorkrebs for the first time. Ontario and Georgia banned Marmorkrebs, and Minnesota is thinking about it.The Ontario ban is quite significant, given the size and population of the province.


Previous year end reviews

2008 was the best year ever for Marmorkrebs research

2009 was tied for the best year ever in Marmorkrebs research

2010 was the best year ever for Marmorkrebs research

2011 was not the best year ever for Marmorkrebs research

2012 was an average year for Marmorkrebs research

2013 was the second best year ever for Marmorkrebs research

2014 was a good year for Marmorkrebs research

2015 was the best year ever for Marmorkrebs research

2016 was the best year ever for Marmorkrebs research

2017 was the second best year ever for Marmorkrebs research

2018 was the second best year ever for Marmorkrebs research

2019 was the second best year ever for Marmorkrebs research

2020 was not the best year for Marmorkrebs research

2021 was the third best year ever for Marmorkrebs research


28 November 2022

Georgia bans Marmorkrebs

Map of USA showing location of state of Georgia
The One Green Planet site is reporting that the southern US state of Georgia has announced plans to ban Marmorkrebs.


The ban would take effect 4 December 2022. A perusal of a public announcement from the Georgia Department of Natural Resources (PDF) seems to show that keeping almost any other crayfish species – except Louisiana red swamp crayfish (Procambarus clarkii) and White river crayfish (Procambarus zonangulus) – would require a permit.


The state and provincial regulations seem to be picking up steam. But I continue to worry about whether these bans are taking into account that there might be researchers who might want to study these animals for scientific purposes.

External links

Georgia Department of Natural Resources Subject 391-4-8 Wild Animals (PDF)

Georgia Rules and Regulations, Subject 391-4-8

Georgia finally expands restrictions on wild animals as pets

Map by TUBS - This SVG locator map includes elements that have been taken or adapted from this locator map:, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15948353

04 November 2022

Minnesota eyes Marmorkrebs ban

 Read the story here.

02 November 2022

Gallardo and colleagues, 2022

Cover to Journal of Applied Ecology

Gallardo B, Sutherland WJ, Martin P, Aldridge DC. 2022. Applying Fault Tree Analysis to biological invasions identifies optimal targets for effective biosecurity. Journal of Applied Ecology 59(10): 2553-2566. https://doi.org/10.1111/1365-2664.14256




  1. The management of invasive species requires analytical tools that can synthesise the increasing and complex information generated through risk assessment protocols. To that end, fault tree analysis (FTA) provides a means to conceptually map all of the events leading to a particular undesired scenario with associated probabilities and uncertainty.
  2. We used a peer-reviewed dataset (the GB Non-Native Species Risk Assessments) to build and quantify a FT of all the events leading to the transport, introduction, establishment and spread of harmful aquatic invasive species in Great Britain. We also simulated management scenarios.
  3. Individual barriers to invasion, either natural or human, were largely unsuccessful in hindering invasion (42%–91% probability of failure in a 5-year period); yet the high interdependence of events in the tree resulted in an overall probability of harmful invasion of about 3%. This figure is much greater than that estimated by the tens rule, which posits that 10% of non-native species manage to colonise a new area, and only 10% of those become invasive, resulting in a 1% overall probability of harmful invasion.
  4. We used the FTA to explore different management intervention scenarios and found that pre-border management reduced the overall risk of invasion by 86%, followed in importance by early action after introduction (85%), and detection at the border (81%). In contrast, post-establishment management techniques, such as eradication and containment, had a limited impact reducing the probability of widespread invasion (18%–24%).
  5. Synthesis and applications. While prevention has been long recognised as the most cost-effective action against biological invasions, here we were able to quantify the reduction in invasion risk under a range of management scenarios. Optimising all management elements included in the FT reduced the overall probability of invasion by three orders of magnitude.
  6. We conclude that FTA provides a baseline to capitalise on a growing source of peer-reviewed risk assessments, which allows systematic assessment of the effectiveness of future actions to prevent and manage invasive species at the national and international levels. The analytical framework can be extended to other biological threats (e.g. pests, pathogens, diseases) and scenarios (e.g. climate change, war), so that breach and leverage points in biosecurity can be identified.

 Keywords: None provided.

Open access

Dobrović and colleagues, 2022

NeoBiota logo

Dobrović A, Geček S, Klanjšček T, Haberle I, Dragičević P, Pavić D, Petelinec A, Boštjančić LL, Bonassin L, Theissinger K, Hudina S. 2022. Recurring infection by crayfish plague pathogen only marginally affects survival and growth of marbled crayfish. NeoBiota 77: 155-177. https://doi.org/10.3897/neobiota.77.87474




Invasive alien crayfish threaten the diversity of freshwater ecosystems and native crayfish fauna. In Europe, this is largely due to transmission of the crayfish plague to susceptible native crayfish. Many invasive species tolerate crayfish plague, but the infection still has the potential to reduce the fitness of a tolerant host due to energy trade-offs between immune response maintenance and life-history traits, such as growth and reproduction. In combination with other unfavourable conditions, such a response could alter further invasion success of an otherwise successful crayfish invader. We examined whether repeated infection with one of the most virulent haplogroups of crayfish plague agent (Aphanomyces astaci) affects growth or survival of the juvenile marbled crayfish (Procambarus virginalis). Juveniles were exposed to i) two levels of pathogen concentrations, and ii) two different feeding regimes under the higher pathogen concentration. In all performed trials, repeated infection reduced growth rates, while the combination of recurring infection and food limitation significantly increased mortality. The average energy cost of the immune response was estimated at 12.07 J/day for individuals weighing 0.3 grams. Since infections were frequent and pathogen concentrations high, results suggest that marbled crayfish is resistant to A. astaci pathogen and its survival is only affected by adding the stress of food limitation. The survival of almost half of the individuals exposed to high pathogen loads and extreme food limitation indicates that chronic infection by crayfish plague is unlikely to be an important factor impeding invasion success of the marbled crayfish, even under harsh conditions. Our results add to the growing body of evidence that marbled crayfish has potential to become one of the most successful freshwater invaders.


Keywords: food limitation • freshwater • immunity cost • infection • invasive species • trade-off

Open access


26 September 2022

Faiad, 2022

University of Washington logo

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


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.

26 March 2022

Retained European Union law says you can’t retain Marmorkrebs in the United Kingdom

Dalek with Union Jack livery
I ran across this article of “pets you can’t have in the United Kingdom” and was a little surprised to see Marmorkrebs on the list. It is banned, along with four other crayfish species (Louisiana red swamp crayfish, signal crayfish, spiny-cheek crayfish, and virile crayfish).

It turns out the regulatory situation in England and Wales (but not Scotland or Northern Ireland?) is a little complicated.


Marmorkrebs were banned in 2016 as part of a European Union intiative. When the United Kingdom left the European Union, the regulations against Marmorkebs stayed as part of “retained EU law.” 

While the government website lists exemptions that people “may” be able to invoke to keep existing pets, it seems none of them would apply to Marmorkrebs. In particular, the “grandfather clause” allowing people to keep existing pets should not apply since Marmrokrebs don’t live as long as the regulations have been in effect.

I also have to snicker a bit about the rule that says if you have one of these animals, you must not let it reproduce. I’m not sure how you are supposed to prevent that in a parthenogenetic animal.

External links


The animals banned as pets in the UK - complete list


Invasive non-native (alien) animal species: rules in England and Wales


Form CRAY2: Application for a licence to keep non-native crayfish

18 March 2022

Katayama and colleagues 2022

COver to journal bioorganic Chemistry

Katayama H, Toyota K, Tanaka H, Ohira T. 2022. Chemical synthesis and functional evaluation of the crayfish insulin-like androgenic gland factor. Bioorganic Chemistry 122: 105738. https://doi.org/10.1016/j.bioorg.2022.105738




Insulin-like androgenic gland factor (IAG) from the marbled crayfish Procambarus virginalis is an insulin-like heterodimeric peptide composed of A and B chains and has an Asn-linked glycan at the B chain. IAG is considered to be a male sex hormone inducing the sex differentiation to male in decapod crustacean, although there is no report on the function of IAG peptide in vivo. In order to characterize P. virginalis IAG, we chemically synthesized it and evaluated its biological function in vivo. A and B chains were prepared by the ordinary solid-phase peptide synthesis, and three disulfide bonds were formed regioselectively by dimethyl sulfoxide oxidation, pyridylsulfenyl-directed thiolysis and iodine oxidation reactions. An IAG disulfide isomer was also prepared by the same manner. Circular dichroism spectral analysis revealed that the disulfide bond arrangement affected the peptide conformation, which was similar to the other insulin-family peptides analyzed so far. On the other hand, the glycan moiety attached at the B chain had no effect on the peptide secondary structure. Injection of the synthetic IAG and its disulfide isomer to female crayfish did not induce male characteristics on the external morphology, but both peptides suppressed the oocyte maturation in vivo. These results suggest that IAG has a pivotal role on the suppression of female secondary sex characteristics.


Keywords: Insulin-like androgenic gland factor •  Procambarus virginalis • peptide synthesis • masculinization

Synthetic insulin-like androgenic gland factor suppressed oocyte formation in marbled crayfish

24 February 2022

Sentis and colleagues 2022

Cover of journal Ecology and Evolution

Sentis A, Veselý L, Let M, Musil M, Malinovska V, Kouba A. 2022. Short-term thermal acclimation modulates predator functional response. Ecology and Evolution 12(2): e8631. https://doi.org/10.1002/ece3.8631




Phenotypic plastic responses to temperature can modulate the kinetic effects of temperature on biological rates and traits and thus play an important role for species adaptation to climate change. However, there is little information on how these plastic responses to temperature can influence trophic interactions. Here, we conducted an experiment using marbled crayfish and their water louse prey to investigate how short-term thermal acclimation at two temperatures (16 and 24°C) modulates the predator functional response. We found that both functional response parameters (search rate and handling time) differed between the two experimental temperatures. However, the sign and magnitudes of these differences strongly depended on acclimation time. Acclimation to 16°C increased handling time and search rate whereas acclimation to 24°C leads to the opposite effects with shorter handling time and lower search rate for acclimated predators. Moreover, the strength of these effects increased with acclimation time so that the differences in search rate and handing time between the two temperatures were reversed between the treatment without acclimation and after 24 h of acclimation. Overall, we found that the magnitude of the acclimation effects can be as strong as the direct kinetic effects of temperature. Our study highlights the importance of taking into account short-term thermal plasticity to improve our understanding of the potential consequences of global warming on species interactions.

Keywords: None provided.


Open access

11 February 2022

Kaliszewicz and colleagues, 2022

The European Zoological Journal cover

Kaliszewicz A, Karaban K, Sierakowski M, Maciaszek R, Kur M, Pyffel Z, Wolny L, Chmiel K, Łuciuk P, Rusin P, Kowalczyk K. 2022. Effect of dietary supplementation with fatty acids on growth, survival, and fatty acid patterns in Procambarus clarkii and Procambarus virginalis: the first comparison of two invasive crayfish species. The European Zoological Journal 89(1): 123-134. https://doi.org/10.1080/24750263.2022.2030420




The red swamp crayfish, Procambarus clarkii, and the marbled crayfish, Procambarus virginalis, are invasive species expanding their ranges on a global scale. Their spread is favored by the fact that these crayfish are also aquaculture species of great economic importance (P. clarkii) or promising prospects in this regard (P. virginalis). This study represents the first attempt to assess the impact of diet supplementation with fatty acids on growth, survival, and fatty acid content in these crayfish species, as well as the first record of fatty acid patterns in the obligate parthenogenetic marbled crayfish. Our results showed that supplementation with saturated palmitic acid increased P. clarkii survival, which has not previously been reported for crustaceans. This positive effect on the part of palmitic acid supplementation was not observed for P. virginalis individuals. Marbled crayfish had significantly higher survival rates than red swamp crayfish regardless of the diet used. The growth of both species was not affected by fatty acid supplementation. Our study indicated that young marbled crayfish had a poorer fatty acid profile than juvenile conspecifics and red swamp crayfish. Fatty acid supplementation and type of diet significantly affected the fatty acid composition in the crayfish tissues. There was an increase in unsaturated α-linolenic acid for P. clarkii and palmitic acid for P. virginalis. Palmitic acid quantitatively dominated in both species regardless of the experimental treatment, with the exception of juvenile P. virginalis, which was fed an oligochaete diet rich in EPA. 


Keywords: red swamp crayfish • marbled crayfish • diet supplementation • saturated fatty acids

05 February 2022

Vogt 2022

The Science of Nature cover

Vogt G. 2022. Studying phenotypic variation and DNA methylation across development, ecology and evolution in the clonal marbled crayfish: a paradigm for investigating epigenotype-phenotype relationships in macro-invertebrates. The Science of Nature 109(1): 16. https://doi.org/10.1007/s00114-021-01782-6


Animals can produce different phenotypes from the same genome during development, environmental adaptation and evolution, which is mediated by epigenetic mechanisms including DNA methylation. The obligatory parthenogenetic marbled crayfish, Procambarus virginalis, whose genome and methylome are fully established, proved very suitable to study this issue in detail. Comparison between developmental stages and DNA methylation revealed low expression of Dnmt methylation and Tet demethylation enzymes from the spawned oocyte to the 256 cell embryo and considerably increased expression thereafter. The global 5-methylcytosine level was 2.78% at mid-embryonic development and decreased slightly to 2.41% in 2-year-old adults. Genetically identical clutch-mates raised in the same uniform laboratory setting showed broad variation in morphological, behavioural and life history traits and differences in DNA methylation. The invasion of diverse habitats in tropical to cold-temperate biomes in the last 20 years by the marbled crayfish was associated with the expression of significantly different phenotypic traits and DNA methylation patterns, despite extremely low genetic variation on the whole genome scale, suggesting the establishment of epigenetic ecotypes. The evolution of marbled crayfish from its parent species Procambarus fallax by autotriploidy a few decades ago was accompanied by a significant increase in body size, fertility and life span, a 20% reduction of global DNA methylation and alteration of methylation in hundreds of genes, suggesting that epigenetic mechanisms were involved in speciation and fitness enhancement. The combined analysis of phenotypic traits and DNA methylation across multiple biological contexts in the laboratory and field in marbled crayfish may serve as a blueprint for uncovering the role of epigenetic mechanisms in shaping of phenotypes in macro-invertebrates.


Keywords: phenotype • development • DNA methylation • ecology • evolution • marbled crayfish

18 January 2022

Marmorkrebs feature in The Guardian

The Guardian
Kate Connolly has written a substantive summary of the state of Marmorkrebs in The Guardian that includes new interviews with several researchers.


The article also prompted some coversation on Twitter about how likely it is that crayfish can help regulate schistosomiasis.


I think my favourite part of the article is a previously undescribed pattern of behaviour: that they are nocturnal:


Lyko recalls driving to a lake about 15 minutes from his lab with his students. Donning head torches and waders and standing ankle deep in the water, “we waited until it got dark, then suddenly they emerged in their hundreds and thousands”, he says.



External links

‘We started eating them’: what do you do with an invasive army of crayfish clones?

Marmorkrebs in Canada?

Premek Hamr drew attention to this record on iN today: a potential Marmorkrebs sighting in City View Park, Burlington, Ontario.


Guenter Schuster suspects that it might be Procambarus, but keying out to species from these pictures is effectively impossible.


That said, local park in an urban environment has been almost exactly the most common pattern we have seen in other locations: someone with an aquarium dumps some unwanted animals into a local park.


This was last October – mere months before Ontario banned Marmorkrebs at the start of 2022. Although Marmorkrebs have done well in some northern locations, it’s hard to tell if they could overwinter in Canada.


Has our luck finally run out? Is this the thin end of the wedge that will be the start of many more invasions of North America?


External links


Marbled crayfish on iNaturalist






15 January 2022

Maiakovska, 2021

University of Heidelberg
Maiakovska O. 2021. Origination, monoclonality and evolution of the marbled crayfish genome Procambarus virginalis. Doctoral dissertation, The Faculty of Bio Sciences, Ruperto Carola University Heidelberg, Germany.




The parthenogenetic marbled crayfish (Procambarus virginalis) sparked interest within the scientific community due to its unique features. Its polyploid and monoclonal genome, high environmental adaptability and phenotypic diversity made the marbled crayfish a suitable laboratory model for genomics, epigenetics and ecology research. The previously established marbled crayfish genome sequence of 3.5 Gbp represents a highly fragmented draft assembly. Initial comparative genomic analyses resulted in confirmation of P. virginalis genome origination from the sexually reproducing freshwater crayfish P. fallax. However, in-depth genomic analysis and interspecies genome comparisons require further refinement of the fragmented genome reference of the marbled crayfish. In this PhD thesis, the first refinement of the marbled crayfish genome has been performed with application of the PacBio Single Molecule Real Time (SMRT) sequencing technology. The new and improved genome assembly of the marbled crayfish resulted in 3.7 Gbp of sequence length and an N50 of 144kb. The refined genome assembly enabled searching parental haplotypes and understanding species origination. The absence of evidence for loss of heterozygosity in the various monoclonal marbled crayfish generations suggests the lack of recombination process during oogenesis. Thus, marbled crayfish suggest to be apomictic parthenogens which are characterized by generating identical copies of the maternal genotype. Moreover, despite of the limited genome variability, monoclonal marbled crayfish genomes consisted of population-specific genetic polymorphisms within the global population. Comparative genomic analysis between geographically distant populations resulted in the identification of population-specific mutational signatures. The calculation of genomic variability of marbled crayfish from the growing population in Lake Reilingen allowed to estimate population dynamics. Thus, the population in Lake Reilingen demonstrates a rapid growth, following the density-independent exponential model. This PhD thesis provides fundamental insights into marbled crayfish research, particularly via making use of an improved genome assembly for comparative genomic analyses, epigenetic studies, and for research on the evolution and genomic adaptation to asexuality.


Keywords: None provided.

14 January 2022

Tŏnges, 2021

University of Heidelberg logo

Tönges SM. 2021. Context-dependent DNA methylation variants in marbled crayfish (Procambarus virginalis). Doctoral dissertation, The Faculty of Bio Sciences, Ruperto Carola University Heidelberg, Germany. https://doi.org/10.11588/heidok.00029299



The marbled crayfish is a recently discovered freshwater crayfish. It is the only known decapod crustacean that reproduces by obligate apomictic parthenogenesis resulting in a clonal, all-female population. All known marbled crayfish have a single origin, and the species is estimated to have an age of about 25-30 years. Furthermore, it has spread already into several countries globally and shows high adaptability to different environments in the absence of genetic adaptation. Epigenetic mechanisms were suggested to play a role in the rapid adaptation of this species. This thesis aims to identify context-dependent DNA methylation variants in marbled crayfish. Samples from two tissues and four distinct habitats were analyzed with a capture-based bisulfite sequencing approach to identify methylation variants. The results were validated by deep amplicon sequencing of tissue-specific and location-specific regions and with newly collected samples from the same tissues and locations as before. The location-specific methylation patterns suggest the existence of epigenetic ecotypes and allow the tracing of the origin of marbled crayfish populations by their DNA methylation fingerprint. In a laboratory trial, single rearing conditions were changed to see the influence of specific parameters on the methylation pattern. Within six months, methylation changes could be observed for the group kept at a lower temperature compared to the control group, indicating the adaptation of the methylation pattern caused by an environmental trigger. Furthermore, the laboratory population showed a different methylation pattern compared to the wild populations. Lastly, the potential of marbled crayfish as an aquaculture livestock was explored, and a framework for an environmentally safe aquaculture was established. Additionally, tracing the origin of marbled crayfish using location-specific methylation patterns was proposed for certifying sustainable and transparent aquaculture practices. These re-sults provide insight into the rapid adaptation in invasive species and provide a proof of concept for environmental origin tracing with DNA methylation fingerprinting.

Keywords: Epigenetics • ecology • aquaculture

Open access

05 January 2022

Marmorkrebs at the ready

Spotted on Reddit:


Marmorkrebs in glass jar labelled, "In case of emergency break glass"


I always worry if Redditors are okay.


External links


Weaponized Marmorkrebs! Don't leave home without one.