01 September 2020

Hossain and colleagues, 2021

Science of the Total Environment cover

Hossain MS, Kubec J, Guo W, Roje S, Ložek F, Grabicová K, Randák T, Kouba A, Buřič M. 2021. A combination of six psychoactive pharmaceuticals at environmental concentrations alter the locomotory behavior of clonal marbled crayfish. Science of The Total Environment 751: 141383. https://doi.org/10.1016/j.scitotenv.2020.141383


Pharmaceutically active compounds (PhACs) are ubiquitous in the aquatic environment worldwide and considered emerging contaminants. Their effects on growth, behavior, and physiological processes of aquatic organisms have been identified even at very low concentrations. Ecotoxicological investigations have primarily focused on single compound exposure, generally at a range of concentrations. In the natural environment, pollutants seldom occur in isolation, but little is known about the effects and risks of combinations of chemicals. This study aimed to investigate the effects of concurrent exposure to six psychoactive PhACs on locomotory behavior and life history traits of clonal marbled crayfish Procambarus virginalis. Crayfish were exposed to ~1 μg L−1 of the antidepressants sertraline, citalopram, and venlafaxine; the anxiolytic oxazepam; the opioid tramadol; and the widely abused psychostimulant methamphetamine. In the absence of shelter, exposed crayfish moved significantly shorter distances and at lower velocity and showed significantly less activity than controls. With available shelter, exposed crayfish moved significantly more distance, showed higher activity, and spent a significantly more time outside the shelter than controls. Molting, mortality, and spawning frequency did not vary significantly between the groups. Hemolymph glucose level did not vary among groups and was not correlated with observed behaviors. Results suggest that environmental concentrations of the tested compounds in combination can alter the behavior of non-target aquatic organisms as individual exposure of these compounds, which may lead to disruption of ecosystem processes due to their reduced caution in stressful conditions. Further research is needed using varied chemical mixtures, exposure systems, and habitats, considering molecular and physiological processes connected to behavior alterations.

Keywords: antidepressant • ethology • emerging contaminant • opioid • Procambarus virginalis

21 August 2020

Benson 2020

Illinois State UNiversity seal
Benson AM. 2020. Identification of innexins contributing to giant-fiber escape responses in marbled crayfish. Master's thesis, School of Biological Sciences, Illinois State University. Stein W, Vidal-Gadea A, advisors. http://doi.org/10.30707/ETD2020.Benson.A


Gap junctions form intercellular pores that coordinate the flow of electrical signals between adjacent cells in the nervous system. While the physiology of electrical synapses has been investigated in sophisticated detail, the molecular underpinnings of electrical signal spread between neurons are not well understood. Even in the crayfish tail flip escape circuit, where electrical synapses have been studied for more than six decades, the gap junction proteins underlying electrical synaptic transmission are unknown. Invertebrate gap junctions are assembled from a diverse family of proteins called innexins (inx), and previous studies have suggested that in each species multiple innexins can contribute to electrical signal spread between cells. In this study, I used the genome and transcriptome assembly of the marbled crayfish, Procambarus virginalis, to identify which innexins are present and expressed in crayfish, and which contribute to the giant fiber tail flip escape response.

My bioinformatics analyses identified 8 putative innexin genes (termed inx1- inx8), only five of which were present in the transcriptome, suggesting that inx6-8 are not necessary for the tail flip. A conserved domain search of inx1 - 5 revealed that only inx1 - 3 contained the sequence signature common to innexins, indicating that inx4 and 5 may not contribute to the functioning of electrical synapses. RNA isolation from the ventral nerve cord (VNC) and brain, which contain distinct giant neurons that mediate the two major crayfish tail-flip responses, further suggested that inx1 - 3 could contribute to the tail flip: the brain expressed two innexins (inx2- 3), whereas the ventral nerve cord expressed three innexins (inx1-3). Basic Local Alignment Search Tool (BLAST) comparisons additionally revealed that inx1 and 2 were homologous to two innexins previously identified to contribute to giant fiber escape responses in insects. To test whether inx1 or 2 contribute to giant fiber tail flips in crayfish, I reduced inx1 and 2 gene expression through RNA interference (RNAi) and measured the behavioral consequences of this diminishment on the tail flip escape response. To elicit RNAi, I created innexin-specific double-stranded RNA (dsRNA) and verified the presence of intact innexin-½ dsRNA at the expected product size of 547 bp.

Animals receiving treatment were injected with 3 µg dsRNA/ g of body weight. A comparison of innexin expression levels between untreated (n = 2), control dsRNA (n = 1), and RNAi (n = 10) treatment groups using quantitative real-time PCR (qPCR) revealed that innexin expression levels diminished two days post-treatment. Behavioral measurements showed that the response latency onset of the tail flip response correlated with innexin expression levels (n = 6). A linear regression revealed a significant correlation between innexin expression and differences in response latency onset for abdominal flexion (p < 0.05, R2 = 0.77) and subsequent extension (p < 0.05, R2 = 0.82). In contrast, the tail flip strength was unaffected by the RNAi treatment (Fig. 20; p > 0.05, R2 = 0.27). Thus, at least one of the two innexins contributes to electrical synaptic transmission in the crayfish tail flip circuit.

Keywords: None provided.

28 July 2020

Marmorkrebs and messed-up childhoods

"What Do You Think You Are?" cover
Brian Clegg is promoting his new book, What Do You Think You Are?, which is coming out next week. As part of his promotion, he has an article in i newspaper about what shapes adult life. (Really, the name of the paper is a single lower case letter i.) The thesis of the article is that your parents and school don’t matter much to your adult life.

Somewhat strangely, Marmorkrebs make an appearance to argue for “chaos” in life outcomes. Clegg writes:

Batches of Marmorkrebs were raised in nearly identical environmental conditions, yet they differed widely. Some were 20 times bigger than others. Some lived twice as long. Their behaviour was totally different. The tiny genetic and environmental differences made a huge difference in outcomes.

The claims here seem to be based on Vogt and colleagues (2008), and they deserve a little examination.

The “nearly identical” environment is bit misleading. Vogt and colleagues noted that the most variation in growth came when crayfish were raised together, and “without shelters, i.e. under conditions of social stress” (emphasis added).

It’s like saying Harry Potter and Dudley Dursley were raised in “nearly identical” conditions. Well, yes, they were generally in the same physical space. But the social reality for the two boys could hardly be more different. Dudley is spoiled. Harry is tolerated at best and harassed at worst.

Similarly, crayfish fight and form hierarchies. Just because crayfish were in the same tank and had ample food does not mean that their experience in the Dursley house – I mean, crayfish tank – is necessarily the same. Nor is it accurate to call that a “tiny” environment difference.

“20 times bigger” is a bit ambiguous. I image that people might imagine one crayfish an inch long and another 20 inches (over a foot and a half) long. But the measurements are mass, not length. Since mass increases with the cube of length, that means one crayfish is about 2.5 longer than another.

I am not sure how different behaviour has to be to count as “totally different.” I’ve watched a lot of crayfish. You can tease differences apart in experiment, but I think most people would have a hard time distinguishing the behaviour of one Marmorkrebs from another. It’s not obvious, like the relaxed dog you see chilling in the dog park and the barky aggro dog you have to keep on the leash.

I don’t know if Marmorkrebs also appear in the book. I hope they do but with perhaps a little more nuance than in this short article.

Related posts

External links
What makes us ourselves? Why your parents might not f*** you up as much as you think


Vogt G, Huber M, Thiemann M, van den Boogaart G, Schmitz OJ, Schubart CD. 2008. Production of different phenotypes from the same genotype in the same environment by developmental variation. The Journal of Experimental Biology 211(4): 510-523. http://jeb.biologists.org/cgi/content/abstract/211/4/510

15 July 2020

Map of Marmorkrebs introductions, now with Austria!

Map of Europe highlighting Austria
I made multiple additions to the big map of Marmorkrebs introductions. The biggest change is the addition of Austria to the list of countries with established Marmorkrebs populations.

The discovery of Marmorkrebs in Salzburg, Austria was published back in 2018 (Latzer and Pekny 2018), but I only just caught up to it today.

Trying to understand that paper (since it was in German) led me to another short abstract describing another Marmorkrebs finding in Austria, this time in Vienna (Moog et al. 2019). This description is brief, so the map position is not precise:

According to Thomas Ofenböck (Municipal Department 45 - Water Management), in August 2018 a single specimen was found in the 22nd district and released in the Mühlwasser.

Released? Oh, that hurts to read.

Finally, I have a more precise position for the location where Marmorkrebs were found in France. Previously, I only had a description of the area from Marc Collas’s tweet. Again, I stumbled upon a much lengthier description of the finding (Collas 2019), which included a map. That allowed me to get a more exact position.

And just to round things out, I added a couple more of sites from Hungary mentioned in Szendőfi and colleagues (2018).

Busy day. Wish I had done this before this year!


Collas M. 2019. Premier signalement de l’écrevisse marbrée (Procambarus virginalis) en Centre de ressources espèces exotiques envahissantes. http://especes-exotiques-envahissantes.fr/premier-signalement-de-lecrevisse-marbree-procambarus-virginalis-en-france/

Latzer D, Pekny R. 2018. Erstnachweis des Marmorkrebses für Österreich in Salzburg. Salzburgs Fischerei 49(3): 24-30. https://issuu.com/lfvs/docs/safisch_3-18

Moog O, Leitner P, Huber T, W. R, Graf W. 2019. Marbled Crayfish (Procambarus virginalis Lykow, (sic) 2017) – a supplement to the list of Aquatic Invertebrate Neozoa in Austria. ECOPROF. https://www.ecoprof.at/index.php/faunaaquaticaaustriaca.html?file=files/ep_downloads/faa/New_Neozoon_Marbled%20Crayfish.pdf

Szendőfi B, Bérces S, Csányi B, Gábris V, Gál B, Gönye Z, Répás E, Seprős R, B. T, Kouba A, Patoka J, Weiperth A. 2018. Egzotikus halfajok és decapodák a Barát‐ és Dera‐patakban, valamint a torkolatuk dunai élőhelyein. Pisces Hungarici 12: 47-51. http://www.haltanitarsasag.hu/ph12/Szendofi_et.al_Pisces.Hungarici_2018.pdf

Collas, 2019

Collas M. 2019. Premier signalement de l’écrevisse marbrée (Procambarus virginalis) en France.   Centre de ressources espèces exotiques envahissantes. http://especes-exotiques-envahissantes.fr/premier-signalement-de-lecrevisse-marbree-procambarus-virginalis-en-france/

(Approximate English translation of title: First report of the marbled crayfish (Procambarus virginalis) in France)


Without abstract. Translated excerpt: 

Following surveys carried out by the Moselle fishing federation, P. virginalis has just been reported for the first time in a natural environment in France, in a body of water in the context of ballast pits on the Moselle catchment area, near Metz. This morphological identification was confirmed by molecular analysis using a mitochondrial gene.

Keywords: None provided.

Moog and colleagues, 2019

Moog O, Leitner P, Huber T, W. R, Graf W. 2019. Marbled Crayfish (Procambarus virginalis Lykow, (sic) 2017) – a supplement to the list of Aquatic Invertebrate Neozoa in Austria. ECOPROF. https://www.ecoprof.at/index.php/faunaaquaticaaustriaca.html?file=files/ep_downloads/faa/New_Neozoon_Marbled%20Crayfish.pdf


The marbled crayfish (Procambarus virginalis Lykow (sic), 2017) is added to the list of aquatic invertebrate neozoa in Austria. The scientifically proven first evidence of marbled crayfish in Austria took place in June 2018 and was published by Latzer & Pekny (2018). The occurrence of the marbled crayfish is so far known only from two ponds in Salzburg (Karlsbader Weiher and pond FBZ I/135; Latzer & Pekny, 2018) and one finding in Vienna. According to Thomas Ofenböck (Municipal Department 45 - Water Management), in August 2018 a single specimen was found in the 22nd district and released in the Mühlwasser. The Mühlwasser is a former branch of the Danube at Stadlau (Vienna, 22. District); since 1875, there is no connection to the river anymore. Although the establishment status of the marble crayfish is unknown, there are two reasons for its inclusion in the list of Austrian aquatic neozoa. 1) the management of the Salzburg state fishing association (Salzburger Landesfischereiverband) must assume that the population cannot be eradicated (personal communication Mrs. Daniela Latzer, Salzburg); 2) an establishment (in the sense of permanent, reproducing populations) is to be assumed since the species reproduces parthenogenetically.

Keywords: None provided.

Latzer and Pekny, 2018

Salzburgs Fischerei 49(3) cover featuring Marmorkrebs
Latzer D, Pekny R. 2018. Erstnachweis des Marmorkrebses für Österreich in Salzburg. Salzburgs Fischerei 49(3): 24-30. https://issuu.com/lfvs/docs/safisch_3-18


Der landesfremde Marmorkrebs wurde nun erstmals in Österreich, und zwar in Salzburg gefunden: dieser Krebs ist auch als sog. „Klon-Krebs" bekannt. Es kommen nur weibliche Tiere vor, die sich parthenogenetisch, also per Jungfernzeugung, fortpflanzen.

Keywords: None provided.

Approximate English translation of abstract:

The foreign marbled crayfish was now in Austria for the first time, specifically found in Salzburg: this crayfish is also known as the “clone crayfish.” Only females come from these animals, which reproduce parthenogenetically, i.e. by means of virgin generation.

Szendőfi and colleagues, 2018

Pisces Hungarici XII cover
Szendőfi B, Bérces S, Csányi B, Gábris V, Gál B, Gönye Z, Répás E, Seprős R, B. T, Kouba A, Patoka J, Weiperth A. 2018. Egzotikus halfajok és decapodák a Barát‐ és Dera‐patakban, valamint a torkolatuk dunai élőhelyein. Pisces Hungarici 12: 47-51. http://www.haltanitarsasag.hu/ph12/Szendofi_et.al_Pisces.Hungarici_2018.pdf

(English title: Occurrence of exotic fish and crayfish species in Barát and Dera
creeks and their adjacent section of the River Danube)


Thermal and urban waters are frequently subjected to the releases of aquatic pets, which often occur in unexpected assemblages of native and non‐native species. To document this, we conducted a half‐year‐long (January – July 2018) field survey the crayfish and fish species present in Barát and Dera creeks (two sampling sites per each) and sections adjacent to their mouth in the River Danube. Sampling sites were inspected monthly using a combination of catching methods. Altogether, four non‐native crayfish, ten nonnative and twelve native fish were recoded. Several individuals of spiny‐cheek crayfish (Faxonius limosus), marbled crayfish (Procambarus virginalis), red swamp crayfish (Procambarus clarkii) and Australian redclaw (Cherax quadricarinatus) were sampled in the thermal water tributary of Barát creek. The Dera creek was not influenced with the thermal or industrial warm water, but the urbanised area affected the water quality, which was still acceptable for occurrence of spiny‐cheek crayfish, marbled crayfish and red swamp crayfish. Besides already well established population of spiny‐cheek crayfish, also marbled crayfish and red swamp crayfish inhabited the River Danube itself. Seven non‐native decapods have been reported in the Hungarian wild so far. However, this is to our knowledge the first published report on co‐occurrence of three North‐American crayfish as well as a combination of North‐American and Australasian crayfish species in Europe. The new faunistic records of exotic live‐bearing fish species from the family Poeciliidae and their hybrids from Barát creek were also obtained. These findings highlight the significance of pet trade as an introduction pathway and thermal as well as urban waters as target sites for new introductions. Roles of established nonnative species and their possible spread are issues requiring further targeted research.

Keywords: biological invasion • thermal water • tributary • Danube

Open access

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. 

External links

Extinction agenda: How border patrols enforce a uniquely rat-free Alberta

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