26 June 2020

Link roundup for June 2020

Friend of the blogGünter Vogt has a write-up for non-specialists about Marmorkrebs at the Atlas of Science.

• • • • •

Great Lakes Now has a story about the efforts to keep invasive species out of the Great Lakes. It starts with Marmorkrebs being banned in Michigan, saying that the new policy made headlines. Other crayfish are discussed more in the article, mostly Louisiana red swamp crayfish.

24 June 2020

Rusch and colleagues, 2020

NeoBiota volume 58 cover featuring crayfish image
Rusch JC, Mojžišová M, Strand DA, Svobodová J, Vrålstad T, Petrusek A. 2020. Simultaneous detection of native and invasive crayfish and Aphanomyces astaci from environmental DNA samples in a wide range of habitats in Central Europe. NeoBiota 58: 1-32. https://doi.org/10.3897/neobiota.58.49358


Crayfish of North American origin are amongst the most prominent high-impact invasive invertebrates in European freshwaters. They contribute to the decline of European native crayfish species by spreading the pathogen causing crayfish plague, the oomycete Aphanomyces astaci. In this study we validated the specificity of four quantitative PCR (qPCR) assays, either published or newly developed, usable for environmental DNA (eDNA) screening for widely distributed native and non-native crayfish present in Central Europe: Astacus astacus, Pacifastacus leniusculus, Faxonius limosus and Procambarus virginalis. We then conducted an eDNA monitoring survey of these crayfish as well as the crayfish plague pathogen in a wide variety of habitat types representative for Central and Western Europe. The specificity of qPCR assays was validated against an extensive collection of crayfish DNA isolates, containing most crayfish species documented from European waters. The three assays developed in this study were sufficiently species-specific, but the published assay for F. limosus displayed a weak cross-reaction with multiple other crayfish species of the family Cambaridae. In the field study, we infrequently detected eDNA of A. astaci together with the three non-native crayfish species under examination. We never detected eDNA from A. astaci together with native crayfish, but in a few locations eDNA from both native and non-native crayfish was captured, due either to passive transport of eDNA from upstream populations or co-existence in the absence of infected crayfish carriers of A. astaci. In the study, we evaluated a robust, easy-to-use and low-cost version of the eDNA sampling equipment, based mostly on items readily available in garden stores and hobby markets, for filtering relatively large (~5 l) water samples. It performed just as well as the far more expensive equipment industrially designed for eDNA water sampling, thus opening the possibility of collecting suitable eDNA samples to a wide range of stakeholders. Overall, our study confirms that eDNA-based screening for crayfish and their associated pathogen is a feasible alternative to traditional monitoring.

Keywords: crayfish plague • eDNA monitoring • eDNA sampling methods • quantitative PCR • TaqMan assay validation

Open access

01 June 2020

Bans on Marmorkrebs could hurt research

If you want to talk about a success story in invasive species management, you might want to talk about the province of Alberta, Canada. Alberta like to boast that it is rat free.

But I can let you in on a little secret. I’ve seen rats in Alberta many times, when I was a student at the University of Lethbridge. Last year, the university got a government grant to build a new rat facility.

So there was a disconnect between declaring “We don’t want this invasive species!” and actually having that species in research labs. The two situations are separable.

I am not sure if that separation will exist for Marmorkrebs, though.

This year, Saskatchewan and Michigan banned Marmorkrebs. Ontario and some other US states are thinking about it.  I have been thinking about what the bans might do for Marmorkrebs research. There are several issues.

First, researchers in those states and provinces might not be able to have Marmorkrebs at all. Some of the Marmorkrebs legislation does not appear to have exceptions for bona fide academic researchers.

For example, the Canadian province of Manitoba has a law against owning all crayfish species, not just Marmorkrebs. In the course of doing research, I once asked officials in Manitoba if a researcher might keep crayfish, and was told, “No.”

Second, if the laws work as intended, fewer people in general would have Marmorkrebs. It’s possible that some pet owners would stop keeping Marmorkrebs, even in jurisdictions where it is completely legal. Aquarium keepers might see “the writing on the wall” and decide not to keep Marmorkrebs any more, in case they become illegal.

This could affect researchers, too. When an animal is widely available in the pet trade, it’s easy for researchers to get them, either for a one-off study or to start a colony.

Crayfish researchers have a long history of asking for regulation of the movement and trade of crayfish. It has been hard to get those regulations, but it would be a shame if new laws were not nuanced enough to allow original research.

If there can be rats in labs in Alberta, we should be able to have crayfish in labs, too. After all, an escaped crayfish in a university building probably has a harder time getting far than an escaped rat would.

Poster from here.

28 May 2020

Velisek and colleagues 2020b

Velisek J, Stara A, Zuskova E, Chabera J, Kubec J, Buric M, Kouba A. 2020. Effects of chloridazon on early life stages of marbled crayfish. Chemosphere 257: 127189. https://doi.org/10.1016/j.chemosphere.2020.127189


The effects of chloridazon exposure at concentrations of 2.7 μg/L (maximal real environmental concentration in the Czech Republic), 27 μg/L, 135 μg/L and 270 μg/L on early life stages of marbled crayfish (Procambarus virginalis) were evaluated. Significantly higher glutathione S-transferase activity and reduced glutathione level was observed at all tested concentrations of chloridazon compared with the control. Chloridazon in concentrations 27, 135 and 270 μg/L caused delay ontogenetic development and slower growth. Histopathological changes in hepathopancreas were found in two highest tested concentrations (135 μg/L and 270 μg/L). Crayfish behaviour was not altered in control vs. exposed animals, while the activity parameters tend to decline with increasing chloridazon concentrations.

Keywords: antioxidant biomarkers • behaviour • early ontogenetic • pyridazinone • toxicity

26 May 2020

Marmorkrebs illegal in Saskatchewan

Map of Canada with Saskatchewan highlightedLast month, Saskatchewan became the first Canadian province to specifically prohibit Marmorkrebs, according to this news article.

“New for this year is a regulatory change that prohibits the collection of crayfish from any Saskatchewan waterbody, as well as prohibitions related to their use as bait for angling,” (Environment Minister Dustin) Duncan said.

Rusty crayfish and marbled crayfish were added to the province’s prohibited species list in April.

I am trying to find the specific policy on Saskatchewan’s Ministry of Environment, but I found nothing through a generic Google search. Will continue to search. The difficulty in finding news about this provincial legislation from last month stands in sharp contrast to the ease of finding about the new policy in Michigan just days ago. Ten points from Saskatchewan.

I found it in the April 3 edition of the Saskatchewan Gazette (PDF) (Table 10 on page 193, to be specific) in a list of prohibited fish.

Yes, a crayfish can be legally considered a fish. Policy is not always about entirely accurate biology. You should read about the legal battles that erupted when scientists started to realize that a whale was not a fish.

External links

Saskatchewan remains free of zebra and quagga mussels
Sakskatchewan Ministry of Environment
Saskatchewan Gazette, 3 April 2020 (PDF)
Trying Leviathan: The Nineteenth-Century New York Court Case That Put the Whale on Trial and Challenged the Order of Nature

23 May 2020

Marmorkrebs in The Times

This a Jeopardy! style post. The answer is:

17 Marbled crayfish or marmorkrebs (Procambarus virginalis). It makes clones of itself from eggs unfertilised by sperm.

The question is one of twenty in today’s Saturday Quiz in The Times!

External links

The Times Saturday Quiz: May 23, 2020

15 May 2020

No Marmorkrebs in Michigan

As expected, Michigan has become the fourth American state (that I know of) to specifically prohibit Marmorkrebs.

This article is quite detailed, and includes a FAQ about what to do if you have marbled crayfish already. To wit:

  • Dispose of it humanely
  • Do not flush it
  • Don’t sell it to someone in another state (that’s also illegal)

It is probably the best resource I have seen from any state that has regulated Marmorkrebs so far.

Update, 18 May 2020: Associated Press (AP) has put this out as one of their syndicated wire stories (e.g., here and here), which is surprisingly wide coverage.

Update, 23 May 2020: Michigan has definitely done the best job of publicizing the policy on Marmorkrebs, probably because of the AP wire story. It’s been reprinted and redistributed by more news organizations than I’ve ever seen for a state. ANd it’ not just reprints. There is some journalism here. For instance, this is a new quote, I think:

“It’s pretty popular in the pet trade, and the decision was not made lightly in terms of it will impact some of the pet trade industry,” said Lucas Nathan, aquatic invasive species coordinator for the Michigan Department of Natural Resources.

As sometimes happens when Marmorkrebs makes the news, I’m happy to see a picture I took being used to illustrate the species.

The coverage here made me laugh:

The (Department of Natural Resources) warns against flushing them down toilets because they may survive. What the DNR probably MEANT to say is, “that's how you get giant self-cloning crayfish roaming the sewer system.”

Related posts

Michigan considering prohibiting Marmorkrebs

External links

Invasive, self-cloning marbled crayfish now a prohibited species in Michigan (Michigan Department of Natural Resources)

Marbled crayfish added to Michigan’s prohibited species list (Associated Press)

Michigan adds invasive marbled crayfish to prohibited species list

Michigan bans marbled crayfish, which reproduces rapidly by genetic cloning

Michigan Outlaws Self-Cloning “Marbled Crayfish”

Self-cloning marbled crayfish banned from Michigan

Great Lakes Commission

Marbled crayfish placed on Michigan’s prohibited species list

12 May 2020

Celebrate diversity: All females, all prawns

Ars Technica has a big feature article on all female crustaceans being used for food, but it’s not Marmorkrebs.

Marmorkrebs are being used as food in Madagascar (see Andriantsoaet al. 2019, 2020) and there is interest in developing them for commercial aquaculture (Jurmalietiset et al. 2019), but there is not much of an existing market for crayfish this small.

Freshwater prawns (Macrobrachium rosenbergii) are another matter. They are widely cultivated and harvested for food in many countries. There was a challenge on The Amazing Race (American version, Season 31, Episode 3) where teams caught them from an indoor fishing center in Vietnam.

I hadn’t been paying close attention to a company called Enzootic that has created a way of making prawns all female. Unlike Marmorkrebs, which are genetically distinct, this company takes advantage of plasticity in sex determination in this species:

It starts by surgically extracting the hormone-producing organ from “donor” males, which are then broken down into individual cells. When the cells are injected into young females, the hormones they produce cause the females to develop as males, despite their chromosomes. Just like natural male prawns, they can mate normally with other females, but some of their offspring possess a unique trait. Known as “super females,” they produce offspring that will develop as females regardless of the chromosomes they carry.

Enzootic has set up the genetics of its shrimp so that these super females are relatively easy to identify, and they can be used to quickly produce large populations of nothing but females.

Some technical papers on this process are Sagi and Aflalo (2005) Mohanakumaran et al. (2006), and Levy et al. (2017).


Andriantsoa R, Jones JPG, Achimescu V, Randrianarison H, Raselimanana M, Andriatsitohaina M, Rasamy J, Lyko F. 2020. Perceived socio-economic impacts of the marbled crayfish invasion in Madagascar. PLOS ONE 15(4): e0231773. https://doi.org/10.1371/journal.pone.0231773

Andriantsoa R, Tönges S, Panteleit J, Theissinger K, Carneiro VC, Rasamy J, Lyko F. 2019. Ecological plasticity and commercial impact of invasive marbled crayfish populations in Madagascar. BMC Ecology 19(1): 8. https://doi.org/10.1186/s12898-019-0224-1

Jurmalietis R, Grickus A, Elstina A. 2019. Marbled crayfish (Procambarus virginalis) as a promising object for aquaculture industry. In: Environment. Technology. Resources. Proceedings of the 12th International Scientific and Practical Conference, Volume 1, pp. 92-95. http://dx.doi.org/10.17770/etr2019vol1.4174

Levy T, Rosen O, Eilam B, Azulay D, Zohar I, Aflalo ED, Benet A, Naor A, Shechter A, Sagi A. 2017. All-female monosex culture in the freshwater prawn Macrobrachium rosenbergii – A comparative large-scale field study. Aquaculture 479: 857-862. https://doi.org/10.1016/j.aquaculture.2017.07.039

Mohanakumaran Nair C, Salin KR, Raju MS, Sebastian M. 2006. Economic analysis of monosex culture of giant freshwater prawn (Macrobrachium rosenbergii De Man): a case study. Aquaculture Research 37(9): 949-954. https://doi.org/10.1111/j.1365-2109.2006.01521.x

Sagi A, Aflalo ED. 2005. The androgenic gland and monosex culture of freshwater prawn Macrobrachium rosenbergii (De Man): a biotechnological perspective. Aquaculture Research 36(3): 231-237. https://doi.org/10.1111/j.1365-2109.2005.01238.x

External links

Can gender-bending Israeli superprawns help feed the world?

Jurmalietis and colleagues, 2019

Jurmalietis R, Grickus A, Elstina A. 2019. Marbled crayfish (Procambarus virginalis) as a promising object for aquaculture industry. In: Environment. Technology. Resources. Proceedings of the 12th International Scientific and Practical Conference, Volume 1, pp. 92-95. http://dx.doi.org/10.17770/etr2019vol1.4174


Marbled crayfish / marmorkrebs, parthenogenetically reproducing decapod crustacean of pet aquarium origin conventionally has been recognized as an undesirable species since it a) is an invasive pest dangerous for aquatic ecosystem resources because of its hardiness, omnivorousness, fast growth, self-cloning abilities; b) has little commercial value for food industry. However, recently an idea has been introduced about marmorkrebs as a promising cheap protein source, which can help to fight world hunger. Accordingly, research performed at Liepaja University (Latvia) was focused on marbled crayfish farming system design issues. Research paper presented discusses marmorkrebs survival capacities in small-volume microcosm tanks (made from recycled material), under harsh abiotic conditions. Pilot research results obtained will be used to develop experimental project on low-input microcosmic indoor aquaculture for marmorkrebs.

Keywords: crayfish • aquaculture • ecological microcosms

27 April 2020

False alarm! There are no Marmorkrebs loose in Canada (that we know of)

There are no Marmorkrebs in Alberta. Well, there are no Marmorkrebs in the wild in Alberta.

After reading this article claiming marbled crayfish had been found in Alberta for years, I reached out to interviewee Nichol Kimmel at Alberta Environment and Parks for more details.

She wrote that the article replaced “Northern crayfish” (also known as the virile crayfish, or Faxonius virilis, formerly known as Orconectes virilis) with “marbled crayfish.” Furthermore, Environment and Parks does not know of any released locations of Marmorkrebs.

This would explain why B.W. Williams, who has extensive knowledge of Canadian crayfish, looked at the article and tweeted:

Right, but most of their photos in that article are of Faxonius virilis, which has spread on its own (expedited postglacial expansion) in many rivers of Alberta; and by bait bucket dumps in portions of the upper South Saskatchewan River (including Bow).

I have removed the Alberta entries in the map of Marmorkrebs introductions.

Related posts

Canadian Marmorkrebs: The North American invasion has begun

External links

This self-cloning crayfish is scuttling into rivers and streams throughout Alberta

25 April 2020

Talasu 2020

Talasu S. 2020. Identifying dopamine receptor genes and transcription marbled crayfish. Presentation given to Illinois Mathematics and Science Academy, 22 April 2020. https://digitalcommons.imsa.edu/sir_presentations/2020/session1/76/


Modulatory transmitters are major contributors to nervous system plasticity and behavioral flexibility, they determine motivational states and are involved in psychiatric and neurological disorders. Neuromodulators act through distinct receptors and the diversity in receptor subtypes and distribution allows a single neuromodulator can exert many different actions. A prerequisite to understand the ways modulators work is to identify which receptors are expressed in an animal.

I studied which Dopamine receptors are present in the Procambarus virginalis also known as Marbled Crayfish, a highly invasive female species with high quality genome and transcriptomes. Their broad behavioral repertoire makes them ideal for studying the actions of neuromodulator receptors. We focused on Dopamine receptors as they play a role in Parkinson’s disease and the reward system of vertebrates and invertebrates.

Using bioinformatics, we identified which dopamine receptors (D2Alpha and D2beta) exist in marbled crayfish. After identifying homologs of both receptors, a conserved domains search revealed no direct functional domains for these putative D2alpha and D2beta receptors. PCR with D2alpha primers on ventral nerve cord mRNA further revealed that this putative receptor is notexpressed in the marbled crayfish nervous system. We are currently testing the expression of D2beta in in the ventral nerve cord.

Keywords: None provided.

24 April 2020

Marmorkrebs are illegal in Idaho

While doing some updates related to the announcement that Marmorkrebs are apparently all over the place in Alberta, I stumbled upon legislation that I was unaware of.

In Idaho, Marmorkrebs is designated “Aquatic Invertebrate Invasive Species” (AIIS). So says the IDAPA 02.06.09 “Rules Governing Invasive Species and Noxious Weeds.” In fact, they are so worried about it that it is listed twice in the current regulations: once as “Marbled Crayfish (Procambarus marmorkrebs)” (sic) and once as “Marmorkrebs Procambarus sp.” (Section 140).

As an invasive species, Idaho says, “No person may possess, cultivate, import, ship, or transport any invasive species.” Unless, that is, you want to eat them. If you want to eat crayfish, you need a permit.

Trying to find when Marmorkrebs was added to this list was difficult, but it seems to have been way back in 2010, based on this administrative bulletin (PDF).

I continue to be extraordinarily frustrated by how hard it is to finding regulations about crayfish on a state to state and province to province level. This law was passed at which this website and blog was already a few years old. Yet it took me a decade to discover this law, even when I keep a specific look out for anything Marmorkrebs related, with Google alerts and more.

I’m reminded of Douglas Adams’s description of what bureaucrats consider “public notice.”

“But the plans were on display…”

“On display? I eventually had to go down to the cellar to find them.”

“That’s the display department.”

“With a flashlight.”

“Ah, well, the lights had probably gone.”

“So had the stairs.”

“But look, you found the notice, didn’t you?”

“Yes,” said Arthur, “yes I did. It was on display in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying ‘Beware of the Leopard.’”

From The Hitchhiker’s Guide to the Galaxy, of course.

External links

Marbled crayfish / Marmorkrebs fact sheet (PDF)
Invasive species of Idaho
IDAPA 02.06.09, Rules Governing Invasive Species and Noxious Weeds (PDF)
Idaho Administrative Bulletin, Volume 10-1 (PDF)

Canadian Marmorkrebs: The North American invasion has begun

Update, 24 April 2020: The CBC news article was wrong. There are no Marmorkrebs in the wild in Canada. See this follow-up post.

I have been wondering for years when I would hear the first confirmed reports of marbled crayfish in the wild in North American, and today is the day.

The Canadian Broadcasting Company (CBC) is reporting not only that Marmorkrebs are in the province of Alberta, but they have apparently been there for some time.

In the last 10 to 20 years however, the marbled crayfish — a crustacean not native to the Bow River — has begun spreading to rivers and lakes throughout Alberta.

It's a problem that Nicole Kimmel, aquatic invasive species specialist for Alberta Environment and Parks, is trying to tackle.

Historically, the crustaceans are normally found in between Wainwright and Ryley in the Beaver River watershed south of Edmonton, Kimmel told The Calgary Eyeopener.

But now they’ve been showing up in water bodies anywhere from the Edmonton area, down to Calgary and Medicine Hat, as well as in the Milk River region.

I’m gobsmacked that marbled crayfish have apparently been out in Alberta for years in multiple locations but that this information apparently never made it out of Alberta, never mind into the scientific literature.

And yet again, people put out origin stories for Marmorkrebs that are not supported by evidence.

Kimmel calls the marbled crayfish a kind of “freak accident” of two crayfish species that may have been imported from Florida into Germany in the ‘90s and were able to mate.

There is no evidence that Marmorkrebs were created by hybridization.

I’ll be following up with the province and seeing if I can discover more. I have not updated the map of Marmorkrebs introductions, but should do soon.

Update: The map of Marmorkrebs introductions now contains general Alberta locations.

External links

This self-cloning crayfish is scuttling into rivers and streams throughout Alberta

23 April 2020

Laurenz and colleagues 2020

Laurenz J, Georg A, Brendelberger H, Lehmann K. 2020. Effects of nitrate on early life stages of Astacus astacus (Linnaeus, 1758) and Procambarus virginalis (Lyko, 2017). International Aquatic Research 12(1): 53-62. https://doi.org/10.22034/iar(20).2020.671232


We examined the effects of nitrate on the embryonic development of two freshwater crayfish species, the indigenous noble crayfish (Astacus astacus) and the invasive marbled crayfish (Procambarus virginalis). Nitrate measurements show concentrations of 50 mg/L in surface waters of Germany, while concentrations in groundwater measure up to 100 mg/L. Performing a chronic exposure experiment, we exposed embryos of both species to nitrate concentrations of between 0.0 mg/L and 500 mg/L to estimate the influences of nitrate concentrations on survival, hatching development time, malformations and growth. We observed the first effects on survival at 14 mg/L LOEC (lowest observed effective concentration) nitrate for marbled crayfish. For noble crayfish, we estimated an EC50 value of 55.7 mg/L on hatching rate. Our results show that eutrophication of surface waters can negatively affect the embryonic development of freshwater crayfish with serious consequences on recruitment.

Keywords: marbled crayfish • noble crayfish • juveniles • nitrate • embryonic

17 April 2020

Michigan considering prohibiting Marmorkrebs

Yesterday, there was a conference call meeting of the Michigan Natural Resources Commission that included discussion of adding Marmorkrebs to the state’s list of invasive species.

The presentation slide deck makes some... interesting statements.

Slide 14 in the deck says, “No native range, presumed product of captive breeding”. This implies that someone deliberately set out to create an asexual crayfish, and that’s misleading at best. There is zero evidence I am aware of that anyone deliberately set out to create an asexual crayfish. Marmorkrebs may have originated in captivity, but nobody planned it. Nobody thought an asexual crayfish was even possible. Nobody was “breeding” for it

Slide 15 says, “Threat to natural resources: Aggressive behavior traits”. This is an odd item to list first. There is no evidence that Marmorkrebs are more aggressive than other crayfish species. The papers on Marmorkrebs fighting to date have shown that they are competitive in when they are facing size-matched individuals from other species. The qualifier is important, because Marmokrebs are smallish crayfish. Many other species get larger, and large animals win. Further, Marmorkrebs have only been compared with a couple of other crayfish species.

The same slide lists another threat as “Introduce disease”. Maybe? Disease has been a big problem with introduced crayfish in Europe, but last I looked at a map, Michigan is not Europe. In the US, disease has usually not been a significant problem with crayfish impacts. It could be. But so far, this seems like one of the lower risks.

I would have inverted this list, and started with “Alter fish communities” and “Degrade water quality”.

The bottom line? The slide deck lists the “next steps” as:
  • Recommend listing Marbled Crayfish as prohibited to DNR-Director
  • Officially list in May, if recommendation is approved
So this process looks quite advanced and likely to happen.

If this went through, this would make Michgan the third North American jurisdiction to regulate Marmorkrebs specifically.

External links

16 April 2020 agenda of Natural Resource Commission (PDF)
Presentations given to the NRC - 16 April 2020, Fish (PDF)

Join in this week’s NRC meeting online or by conference call

16 April 2020

Andriantsoa and colleagues, 2020

Andriantsoa R, Jones JPG, Achimescu V, Randrianarison H, Raselimanana M, Andriatsitohaina M, Rasamy J, Lyko F. 2020. Perceived socio-economic impacts of the marbled crayfish invasion in Madagascar. PLOS ONE 15(4): e0231773. https://doi.org/10.1371/journal.pone.0231773

The negative environmental and economic impacts of many invasive species are well known. However, given the increased homogenization of global biota, and the difficulty of eradicating species once established, a balanced approach to considering the impacts of invasive species is needed. The marbled crayfish (Procambarus virginalis) is a parthenogenetic freshwater crayfish that was first observed in Madagascar around 2005 and has spread rapidly. We present the results of a socio-economic survey (n = 385) in three regions of Madagascar that vary in terms of when the marbled crayfish first arrived. Respondents generally considered marbled crayfish to have a negative impact on rice agriculture and fishing, however the animals were seen as making a positive contribution to household economy and food security. Regression modeling showed that respondents in regions with longer experience of marbled crayfish have more positive perceptions. Unsurprisingly, considering the perception that crayfish negatively impact rice agriculture, those not involved in crayfish harvesting and trading had more negative views towards the crayfish than those involved in crayfish-related activities. Food preference ranking and market surveys revealed the acceptance of marbled crayfish as a cheap source of animal protein; a clear positive in a country with widespread malnutrition. While data on biodiversity impacts of the marbled crayfish invasion in Madagascar are still completely lacking, this study provides insight into the socio-economic impacts of the dramatic spread of this unique invasive species. “Biby kely tsy fantam-piaviana, mahavelona fianakaviana” (a small animal coming from who knows where which supports the needs of the family). Government worker Analamanga, Madagascar.

Keywords: None provided.

Note: Co-author Julia Jones provides a summary of this paper and some personal commentary in a Twitter thread. Excerpt:

Fozaorana (Procambarus virginalis to give them their scientific name) became synonymous in Malagasy with something cheap and poor quality. Cheap burner phones are called fozaorana for example. ... (O)ur recent paper shows that (especially in areas which have been invaded longer), people tend to quite appreciate the crayfish & feel they make a positive impact in food security and livelihoods.

09 April 2020

Coronavirus cancels crayfish conference

This year’s International Association of Astacology conference is not happening, due to COVID-19 concerns. The next meeting is scheduled for 2021.

(I should say, “tentatively scheduled,” since we don’t know how long this pandemic is going to go on.)

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
Province seeks input on 13 invasive species

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.)