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