29 March 2020

Commerical eDNA testing for Marmorkrebs

SureScreen Scientifics logo

The English company SureScreen Scientifics is offering commercial environmental DNA (eDNA) testing for the detection of Marmorkrebs. This is, as far as I am aware, the first commercial product or service that is specifically designed around Marmorkrebs, besides the sale of animals.

The rationale and context for this service is very much geared to monitoring white-clawed crayfish (Austropotamobius pallipes) populations in the UK.

The white-clawed crayfish is the only native crayfish species in the UK. It is endangered and under threat from invasive crayfish species such as signal crayfish and the crayfish plague. Our simple to use eDNA test provides a cost-effective opportunity to monitor these species.

The company’s main web page says they use eDNA to check for:

  • White-clawed crayfish (Austropotamobius pallipes)
  • Signal crayfish (Pacifastacus leniusculus)
  • Marbled crayfish (Procambarus virginalis)
  • Crayfish plague (Aphanomyces astaci)

The company’s technical white paper (PDF here) say they can also test for Lousiana red swamp crayfish (Procambarus clarkii) and two European species, narrow-clawed crayfish (Astacus leptodactylus) and noble crayfish (Astacus astacus). It’s not clear why these other three species are not listed on the main web page.

The ability to test for Marmorkrebs (and highlighting this on the main web page) is interesting, because there are no confirmed introductions of Marmorkrebs in the islands of Great Britain or Ireland.

On the other hand, the other four crayfish species that the company can tests for (P. leniusculus, P. clarkii, A. leptodactylus, and A. astacus) are already established in the UK (Peay et al. 2010). So are two other species, the virile crayfish (Faxonius limosus) and spiny-cheeked crayfish (Faxonius limosus) are also already in the UK.

I think there’s an interesting question of which should be the priority in developing a test: for the Faxonius species that we already know are there, or for species like Marmorkrebs that could be lurking there, undetected.

While the company is based in England, and is clearly attempting to fill a need for monitoring UK waterways, there is no reason I could see that they couldn’t handle samples from anywhere in the world.

By the way, nobody at SureScreen Scientifics paid me to say this.


Peay S, Holdich DM, Brickland J. 2010. Risk assessments of non-indigenous crayfish in Great Britain. Freshwater Crayfish 17: 109-122. http://iz.carnegiemnh.org/crayfish/iaa/fc17_toc.htm#

External links

SureScreen Scientific crayfish page

Mad about Marmorkrebs (mad angry, not mad interested)

A question on Quora popped up: “If Wikipedia is correct, how can people believe the speciation story of the Marbled Cray actually occurred?” I summarized the available science, which prompted this fascinating comment.

That the MC’ has 3 chromosomes, because it had 3 chromosomes when the scientists, (or whoever claimed a speciation occurred), (Your buddies), went to the German village, collected some live MC’s, thereon the person ‘creating’ the sham event, did put baby MC’s into the tank with Slough Cray’s……

It is obvious that Wiki are driven by Evolutionists like yourself, and writing a paper on how your mates say the sham speciation event occurred, is of no consequence to the reality that: The MC was ‘Created” a very long time ago with 3 chromosomes to be capable of self replication, to help feed the people, the German Traders at the Village has already stated to the world, that they were trading the MC’ for generations, hence, the MC’ simply has, and always had 3 chromosomes….

And your “Manufactured” series of events, are simply a stab in the dark, because the MC’ was placed in the tank, and people like you, then Peddle the sales pitch……… That is the TRUTH is it not

The internet is wonderful, because it lets you know what people think.

External links

If Wikipedia is correct, how can people believe the speciation story of the Marbled Cray actually occurred?

26 March 2020

Maple leaf Marmorkrebs in the future?

The newest issue of Crayfish News from the International Association of Astacology features a nice little article by Premek Hamr on Canadian crayfish, which briefly mentions Marmorkrebs.

(T)wo additional species are likely to expand into Canada in the near future. The marbled crayfish (Procambarus virginalis) is a parthenogenetic species which originated from the German aquarium pet trade and has established in the wild in several European countries as well as Madagascar (Vogt, 2018). It is for sale in Canada from some pet dealers as well as private aquarists over the internet. Single and multiple specimens are available for sale for prices ranging between 1 and 15 CAD (Hamr, unpublished data). Since it survives in the wild in central Europe, it is very likely to escape and establish wild populations in the warmer parts of Canada such as Southern Ontario and coastal British Columbia. So far, it has not been documented in the wild in Canada to date but a release appears to be imminent (Hamr, unpublished data).

Imminent? Maybe. I agree that it will probably happen. But having tracked Marmorkrebs introductions for some years now, I have been surprised that there were not confirmed introductions and established populations in North America years ago now.

For some data on the trade in crayfish in Canada, see this paper.


Hamr P. 2020. The classification, status and distribution of Canadian crayfishes: an update. Crayfish News 42(1): 1, 3-5.

External links

Crayfish News archive

23 March 2020

Linzmaier and Jeschke, 2020

Cover of Freshwater Biology 65(4)
Linzmaier SM, Jeschke JM. 2020. Towards a mechanistic understanding of individual-level functional responses: Invasive crayfish as model organisms. Freshwater Biology 64(4): 657-673. https://doi.org/10.1111/fwb.13456


  1. In novel communities, a rising number of new and emerging invasive species interact with resident species, some of which are non‐native themselves. We implemented an innovative trophic interaction framework for novel communities and quantified the interaction strength and impact potential of a truly novel species (marbled crayfish Procambarus virginalis) with a resident non‐native counterpart (spiny‐cheek crayfish Faxonius limosus). As prey, we used Dreissena mussels, which are non‐native as well and now hold a key position in many European and North American aquatic ecosystems.
  2. For both crayfish species, we predicted functional responses based on a mechanistic model that we parameterised with a set of experimental observations of foraging behaviour and satiation. We compared these predicted functional responses to empirically observed responses. In addition, we incorporated behavioural traits such as aggression, activity, and boldness in the comparisons between the species and individuals to determine their influence on functional responses. We tested individuals from aquarium stocks as well as naturalised individuals from invaded water bodies.
  3. Altogether, we performed 1,095 experiments with 26 individual crayfish. We found that per capita predation of spiny‐cheek crayfish exceeded that of marbled crayfish from aquaria and naturalised individuals. Functional responses differed between species and were mostly higher for spiny‐cheek crayfish males. Marbled crayfish, however, were more voracious and reached satiation more slowly. Consumption rates correlated with aggression for marbled crayfish and with an aggressive threat response for spiny‐cheek crayfish.
  4. We conclude that spiny‐cheek crayfish can reach higher short‐term consumption rates than marbled crayfish, but both species probably do not substantially affect Dreissena mussel populations in the field. For marbled crayfish, high long‐term consumption, interspecific aggression, and reproduction rates can promote their establishment and spread. Risk assessments of these invaders should be improved by considering numerical responses, and different prey organisms and predators.

Keywords: biological invasions • foraging • freshwater crayfish • functional response •  mechanistic model • predator–prey interactions • trait variation

Nature, nurture, noise

A new feature by Jordana Cepelewicz in Quanta Magazine starts off using marbled crayfish to make a point about variation:

In the 1990s, an army of clones invaded Germany. Within a decade, they had spread to Italy, Croatia, Slovakia, Hungary, Sweden, France, Japan and Madagascar — wreaking havoc in rivers and lakes, rice paddies and swamps; in waters warm and cold, acidic and basic. The culprits: six-inch-long, lobster-like creatures called marbled crayfish. ...

New research on crayfish and scores of other organisms is revealing an important role for a third, often-overlooked source of variation and diversity — a surprising foundation for what makes us unique that begins in the first days of an embryo’s development: random, intrinsic noise.
Marmorkrebs are not the point of the article, but it’s nice to see them so prominent featured. It’s a nice example of how marbled crayfish can be used as a model for general biological problems.

External links

Nature Versus Nurture? Add ‘Noise’ to the Debate.

29 February 2020

Yonvitner and colleagues, 2020

Yonvitner Y, Patoka J, Yuliana E, Bohatá L, Tricarico E, Karella T, Kouba A, Reynolds JD. 2020. Enigmatic hotspot of crayfish diversity at risk: Invasive potential of non-indigenous crayfish if introduced to New Guinea. Aquatic Conservation: Marine and Freshwater Ecosystems 30(2): 219-224. https://onlinelibrary.wiley.com/doi/abs/10.1002/aqc.3276


  1. The large island of New Guinea has a rich indigenous astacofauna represented by numerous parastacids from the genus Cherax. The western half of the island is part of Indonesian territory.
  2. Indonesia is known to be the main exporter of ornamental crayfish globally, and certain New Guinean species are exploited as ornamentals within the international pet trade. Moreover, one non‐indigenous species has been previously recorded being cultured in Java, Indonesia. This species, the North American Procambarus clarkii, is a vector of crayfish plague, the disease that is lethal to most parastacids. This population has already tested positive for the disease.
  3. As the transport of non‐indigenous crayfish within the Indonesian territory is not restricted, their introduction to New Guinea can be expected. The Indonesian market was therefore surveyed for ornamental crayfish and their environmental suitability evaluated, as represented by temperature during the drought and rainy seasons in New Guinea.
  4. Four North American and one Australian species were found advertised for sale. One of them, P. clarkii, was assessed as the most damaging species, followed by other North American species. A total ban on the culture and transport of the highest risk crayfish species in Indonesia and Papua New Guinea is recommended.

Keywords: Cambaridae • Cherax • climate matching • EICAT • Indonesia • MaxEnt • Parastacidae • pet trade • risk assessment

Hossain and colleagues, 2020

Hossain MS, Guo W, Martens A, Adámek Z, Kouba A, Buřič M. 2020. Potential of marbled crayfish Procambarus virginalis to supplant invasive Faxonius immunis. Aquatic Ecology: 54: 45-56. https://doi.org/10.1007/s10452-019-09725-0


Biological invasions are a growing threat to global biodiversity due to negative impacts on native biota and ecosystem functioning. Research has expanded from investigating native and alien species interactions to examining relationships among alien species. Invasive crayfish may have similar life histories, niche preferences, and adaptation strategies, but their mutual interactions are little understood. This study aimed to quantify interaction patterns of size-matched calico crayfish Faxonius immunis, established in the Rhine River catchment, and the parthenogenetic marbled crayfish Procambarus virginalis, currently spreading throughout Europe. During agonistic interactions in the absence of shelter, marbled crayfish won a significant majority of fights against calico crayfish, but in the presence of shelter there was no significant difference. When sex of calico crayfish was considered in the analysis without shelter, marbled crayfish won a significantly higher number of fights with female calico crayfish. In the absence of shelter, marbled crayfish dominated calico crayfish females in 83.3% and males in 60% of pairs. With available shelter, the dominance of marbled crayfish was 100% and 54.5% over female and male calico crayfish, respectively. The results suggested that sex and resource availability influence agonistic behaviour in the studied crayfish. Marbled crayfish are confirmed to be competitive against the calico crayfish, which has been shown to be dominant over another serious invader in the Rhine River catchment, the spiny-cheek crayfish Faxonius limosus. In natural sympatric populations, the situation may be affected by factors such as size, reproductive variables, water temperature, and predation pressure.

Keywords: biological invasion • calico crayfish • competition • dominance • interaction • marbled crayfish

Tönges and colleagues, 2020

Tönges S, Masagounder K, Gutekunst J, Lohbeck J, Miller AK, Böhl F, Lyko F. 2020. Physiological properties and tailored feeds to support aquaculture of marbled crayfish in closed systems. bioRxiv: 2020.2002.2025.964114. https://doi.org/10.1101/2020.02.25.964114 (Unreviewed preprint)


The marbled crayfish (Procambarus virginalis) is a new freshwater crayfish species, which reproduces by apomictic parthenogenesis, resulting in a monoclonal, all-female population. The animals have become a popular source for nutritional protein in Madagacar and are increasingly being considered for commercial aquaculture. However, their potential has remained unclear and there are also significant ecological concerns about their anthropogenic distribution. We show here that the size and weight of marbled crayfish is comparable to commonly farmed freshwater crayfish. Furthermore, purification of chitin from marbled crayfish shells revealed a high chitin content, which can be utilized for the synthesis of chitosan and other bioplastics. To allow the further evaluation of the animals in closed aquaculture systems, we used a factorial modeling approach and formulated tailored feeds that were matched to the marbled crayfish amino acid profile. These feeds showed superior performance in a feed trial, with a noticeable feed conversion rate of 1.4. In conclusion, our study provides important data for a balanced assessment of marbled crayfish as a new species for sustainable aquaculture and a feed that allows their culture in closed systems.

Keywords: None provided.

27 February 2020

PhD position with Marmorkrebs

A doctoral position to study “Marbled crayfish as a model organism” is available! The position is in Czechia with Antonín Kouba. More information about the position are here.

24 February 2020

Canadian province of Ontario asks for input on Marmorkrebs

Ontario Ministry of Natural Resources and Forestry logo
Marmorkrebs may be added to Ontario’s invasive species list.

Several news outlets are reporting that the province’s Ministry of Natural Resources and Forestry is seeking public feedback concerning thirteen new species that might be added to the list.

Besides Marmorkrebs, the Louisiana red swamp crayfish (Procambarus clarkii) is another contender for regulation. If either was added, they would join one crayfish that is already regulated in Ontario, the Australian yabby (Cherax destructor).
A link to the Ontario government’s feedback page can be found here. The ministry says it will keep consultation open until 30 March 2020.

I highly recommend any crayfish biologists, particularly those with expertise in Marmorkrebs, complete the feedback form.

External links

Ontario taking action against invasive species
Province asking for feedback on invasive species
MNRF wants your opinion on 13 invasive species from wild pigs to red swamp crayfish

23 January 2020

Velisek and colleagues, 2020

Velisek J, Stara A, Kubec J, Zuskova E, Buric M, Kouba A. 2020. Effects of metazachlor and its major metabolite metazachlor OA on early life stages of marbled crayfish. Scientific Reports 10(1): 875. https://doi.org/10.1038/s41598-020-57740-1


The effects of the herbicide metazachlor and its major metabolite metazachlor OA at two concentrations, including environmentally relevant concentrations of metazachlor (0.0115 µmol/l and 0.0790 µmol/l) and metazachlor OA (0.0117 µmol/l and 0.0805 µmol/l), respectively, were evaluated on early ontogeny, growth, behaviour, oxidative stress, antioxidant enzyme levels, histology, and mortality of marbled crayfish Procambarus virginalis. Both tested concentrations of metazachlor and metazachlor OA were associated with significantly lower growth and delayed ontogenetic development compared to controls. Exposure of metazachlor at 0.0115 µmol/l and metazachlor OA at 0.0117 µmol/l and 0.0805 µmol/l resulted in significantly lower activity of total superoxide dismutase (SOD), catalase (CAT), glutathione s-transferase (GST), glutathione reductase (GR), and reduced glutathione (GSH) compared with control and resulted in gill anomalies ranging from wall thinning to focal disintegration of branchial structure. Metazachlor at the environmentally relevant concentration of 0.0790 µmol/l was associated with significant alterations of crayfish distance moved and walking speed. The potential risk associated with metazachlor use in agriculture related to effects on non-target aquatic organisms.

Keywords: None provided.

21 January 2020

Vogt, 2020

Vogt G. 2020. Biology, ecology, evolution, systematics and utilization of the parthenogenetic marbled crayfish, Procambarus virginalis. In: Ribeiro FB (ed.), Crayfish: Evolution, Habitat and Conservation Strategies, pp. 137-227. Nova Publishers: Hauppauge. https://novapublishers.com/shop/crayfish-evolution-habitat-and-conservation-strategies/


The marbled crayfish, Procambarus virginalis, is the only obligately parthenogenetic species of the 15,000 decapod crustaceans. This chapter describes its detection history, biology, taxonomy, geographical distribution, ecology, evolution and utilization. The marbled crayfish was detected in 1995 in the German aquarium trade. Morphological and genetic evidence suggests that it has arisen by autotriploidy from slough crayfish, Procambarus fallax, which is native to Florida and southern Georgia. Since marbled crayfish was neither described in the extensive biogeographical literature on crayfishs of this region nor found in respective museum collections it is thought to have originated in evolutionarily recent times, perhaps in captivity. Genetic investigations revealed that marbled crayfish is of single origin and monoclonal. Comparison of morphology, life history, genetics, reproduction, behavior, ecology and biogeography between marbled crayfish and its parent species and application of the Evolutionary Genetic Species Concept for Asexuals suggests treating marbled crayfish as a separate species rather than keeping it as a parthenogenetic lineage within Procambarus fallax. Beginning in the late 1990s, marbled crayfish was spread from Germany across the world. Releases have led to the establishment of wild populations in 16 countries on three continents. In Madagascar, marbled crayfish has already invaded a considerable proportion of the country. Behavioral and ecological data suggest that marbled crayfish can compete with other crayfish species, even with much bigger ones. Despite of genetic uniformity, marbled crayfish have adapted to a wide range of habitats in tropical to cold-temperate biomes. This was apparently possible by their capability to produce different phenotypes from the same genome by epigenetic mechanisms. Because of genetic identity, high fecundity, easy rearing, the availability of a draft genome and further advantages, the marbled crayfish is increasingly being used as a laboratory model for research including development, neurobiology, behavior, reproduction, toxicology, stem cell biology, genetics, epigenetics, and invasion biology. In Madagascar, wild marbled crayfish stocks are exploited as a food commodity.

Keywords: biogeography • competition • ecology • evolution • invasion • marbled crayfish • parthenogenesis • research model • systematics • exploitation

14 January 2020

Vogt, 2019

Vogt G. 2019. Estimating the young evolutionary age of marbled crayfish from museum samples. Journal of Natural History 53(39–40): 2353–2363. https://doi.org/10.1080/00222933.2019.1702730


The obligately parthenogenetic, all-female marbled crayfish, Procambarus virginalis, is a triploid descendant of the similarly looking, sexually reproducing slough crayfish, Procambarus fallax, native to Florida and southern Georgia. We have earlier hypothesised that marbled crayfish may have originated from P. fallax only some 25 years ago, perhaps in captivity. In order to investigate the young evolutionary age hypothesis in more detail, I searched the P. fallax collection of the Smithsonian Institution Museum of Natural History (USNM, Washington, D.C.) for evidence of marbled crayfish before its detection in the German aquarium trade in 1995. In particular, I analysed the sex ratio of P. fallax and the frequency of pure female samples throughout its entire distribution range to detect potentially misidentified marbled crayfish among the P. fallax. If marbled crayfish had originated from P. fallax long ago, spread throughout Florida and Georgia and erroneously been sampled as P. fallax, then the sex ratio of the P. fallax in the collection should be significantly biased towards females and pure female samples should be much more frequent than in related Procambarus species. Comparison of P. fallax (n = 2299) with its closest relatives P. seminolae (n = 801) and P. leonensis (n = 150) revealed female proportions of 55.33%, 53.93% and 54.67%, respectively, which are not significantly different from each other. The average female proportion of the 14 Procambarus species investigated (8641 specimens) was 52.54 ± 7.54% (mean ± standard deviation). Moreover, pure female samples consisting of more than 3 specimens that could represent hidden marbled crayfish were not conspicuously more common in P. fallax (2.33%) than in all Procambarus species investigated (1.24 ± 1.79%). These data suggest that the P. fallax collection of the USNM consists of real, sexually reproducing P. fallax and does most likely not include hidden marbled crayfish, supporting the young evolutionary age hypothesis for marbled crayfish.

Keywords: Marbled crayfish • evolution • Procambarus • museum collection • sex ratio

06 January 2020

2019 was the second best year ever for Marmorkrebs research

I am a little late, but the tradition continues!

This is a conservative estimate of the research activity around Marmorkrebs, because it only includes journal articles, not doctoral theses or the Forum Flusskrebse articles and the like.

As with previous years, the articles are roughly evenly split between interest in Marmorkrebs as a lab animal used for basic research, and Marmorkrebs as an potential or actual invasive species. And indeed, reports emerged (not yet published) of Marmorkrebs in three more countries: France, Denmark, and Israel. The latter is the first report from the Middle East.

Like their introductions into natural ecosystems, the research trendline shows no signs of slowing down.

Update, 14 January 2020: Another paper came out with a 2019 cover date, so the graph is now updated!

Related posts

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

04 January 2020

Lyko, 2020

Lyko F. 2020. Epigenetic adaptation in a clonal invasive crayfish. Symposium presentation at Society for Integrative and Comparative Biology, 3-7 January 2020, Austin, Texas, USA. http://vps40083.inmotionhosting.com/~sicb/meetings/2020/schedule/abstractdetails.php?id=3


The parthenogenetic marbled crayfish (Procambarus virginalis) is a novel species that has rapidly invaded and colonized various different habitats. Remarkably, adaptation to different environments appears to be independent of the selection of genetic variants, as marbled crayfish represent an evolutionary young and genetically homogeneous clone. It therefore seems likely that marbled crayfish adaptation depends on epigenetic mechanisms. We have recently established the complete genome sequence of the marbled crayfish and identified an active DNA methylation system, thus establishing the capacity for epigentic regulation of this genome. We are now using integrated analysis of DNA methylation, chromatin and gene expression datasets to characterize the regulatory mechanism(s) used for epigenetic adaptation in marbled crayfish. In addition, we are analyzing epigenetic modification patterns of animals from ecologically distinct habitats at the population scale. Our results provide novel insights into invertebrate DNA methylation and its function in adaptive gene regulation.

Keywords: None provided.

(Note: This presentation was scheduled to be part of the symposium, “Building Bridges from Genome to Phenome: Molecules, Methods and Models.” It was not presented due to author’s inability to travel.)