24 October 2020

Poland also has Marmorkrebs

Map of Poland in Europe
While I was busy updating the marbled crayfish Wikipedia page with yesterday’s news that Marmorkrebs had been found in the waters of Belgium, I noticed another country on the list I hadn’t seen before.


Poland. Poland?


Yes. Last month, news reports came out about Marmorkrebs in Poland. And nobody told me! Presumably my automatic email alerts failed because I don’t have alerts for whatever the Polish word for “crayfish” is.


Not only are they in Poland, one article says that these may be amo ng the largest populations. The Polish lakes are estimated to have tens of thousands of individuals.


As usual, I have some fact-checking to do on the news report, since there is no scientific paper yet. Both articles say:


(T)he young produce eggs by themselves after about 2-3 months.


That’s much faster than the reproductive cycle in the literature. From hatching to first reproduction usually takes 7 months (Seitz et al 2005).


One article says:

The lack of males in this species makes it impossible to use pheromone methods or introduce genetically modified males as competition - the scientist explains.


Agree that genetically modified males wouldn’t work. 


I’m not sure what “pheromones” is referring to. I don’t know off the top of my head of any attempt to use pheromones to control crayfish populations. But the lack of males may not be an obstacle, since Marmorkrebs still show sexual behaviour (Vogt et al. 2015). They might still respond to pheromones.


Predatory species of fish also cannot cope with it. Marbled crayfish kills catfish, pike, zander and perch.


This is a weird claim. I don’t know of any fish that has too much of a problem taking out crayfish. Marbled crayfish could kill fish when they’re small, maybe. But this makes it sound like Marmorkrebs are somehow invincible to these fish regardless of size.

The Epicrates Foundation has been doing quite a bit of work on this, working with a nearby national park to try to stem the Marmorkrebs from entering park waters.

Additional: Gregor Kasimatis mentions a 2018 survey in Poland found no Marmorkrebs.

External links


Epicrates Foundation (Facebook)


Raki mutanty już tu są. Niosą zagrożenie koło Włodawy i nie potrzebują do rozmnażania samców (Translation: “Crayfish mutants are already here. They pose a threat near Włodawa and do not need males to breed”)


W naszym regionie odkryto ogromną populację zmutowanych raków. Stanowią one ogromne zagrożenie dla ekosystemu (zdjęcia) (Translation: “A huge population of mutant crayfish has been discovered in our region. They pose a huge threat to the ecosystem (photos)”


Rak marmurkowy zagrożeniem dla Poleskiego Parku Narodowego (Translation: Marbled crayfish as a threat to the Poleski National Park) 




Seitz R, Vilpoux K, Hopp U, Harzsch S, Maier G. 2005. Ontogeny of the Marmorkrebs (marbled crayfish): a parthenogenetic crayfish with unknown origin and phylogenetic position. Journal of Experimental Zoology A 303(5): 393-405. http://dx.doi.org/10.1002/jez.a.143


Vogt G, Falckenhayn C, Schrimpf A, Schmid K, Hanna K, Panteleit J, Helm M, Schulz R, Lyko F. 2015. The marbled crayfish as a paradigm for saltational speciation by autopolyploidy and parthenogenesis in animals. Biology Open 4(11): 1583-1594. http://dx.doi.org/10.1242/bio.014241

23 October 2020

Belgium falls to Marmorkrebs

Map of Europe highlighting Belgium

The Brussels Times is reporting that Marmorkrebs popping up in several locations in Brussels. It’s not clear when they were first spotted, but their success in one location, a cemetery in Antwerp, was enough to warrant coverage.


The map of Marmorkrebs introductions has been updated accordingly.


It’s almost reaching the point where it will be faster to list European countries without Marmorkrebs rather than with.


An article in the Telegraph is paywalled, but I’m not hopeful about it given the preview text says:


 Escaped self-cloning mutant crayfish created in experimental breeding programmes...


No. That’s some bullshit right there. There is no evidence Marmorkrebs were “created” by experiments. It’s a weird myth that seems to have no discernible origin.


External links


Hundreds of self-cloning crayfish invade Antwerp cemetery


Escaped cloned female mutant crayfish take over Belgian cemetery

20 October 2020

Linzmaier and colleagues 2020

BIological Invasions cover
Linzmaier SM, Musseau C, Matern S, Jeschke JM. 2020. Trophic ecology of invasive marbled and spiny-cheek crayfish populations. Biological Invasions 22: 33393356. https://doi.org/10.1007/s10530-020-02328-z




North American cambarid crayfish have been highly successful in establishing and spreading across Europe and are now over-invading earlier arrivals in many water bodies. Parthenogenetic marbled crayfish (Procambarus virginalis), which originated from aquarium stocks, are relatively recent invaders and have established in lakes previously invaded by spiny-cheek crayfish (Faxonius limosus). However, the feeding ecology of marbled crayfish and consequential impacts on the non-native species’ coexistence are largely unexplored. By combining laboratory experiments with stable isotope analyses of field samples, we were able to (1) determine food preferences of both species under controlled conditions and (2) explore their trophic niches in three lakes where both species co-occur. In the food-choice laboratory experiments, the two species showed similar food preferences and consumption rates. Consistently, the stable isotope analyses (δ13C and δ15N) highlighted the intermediate trophic position of both species. Marbled crayfish and spiny-cheek crayfish occupied a wide range of trophic positions corresponding to a very generalist diet. However, marbled crayfish were more relying on arthropod prey than spiny-cheek crayfish which fed more on mollusks. This is the first work providing evidence for trophic plasticity of marbled crayfish in lake food webs. Our results suggest that the addition of marbled crayfish increases grazing pressure on macrophytes and macrophyte-dependent organisms and the allochthonous detritus decomposition in ecosystems already invaded by spiny-cheek crayfish. Since both species are listed as invasive alien species of EU concern, further assessments of potentially endangered food organisms are needed.

Keywords: prey choice • food selection • stable isotope analysis • over-invasions • MixSIAR • functional equivalence • trophic niche

Roje and colelagues 2020

Aquatic Sciences cover
Roje S, Švagrová K, Veselý L, Sentis A, Kouba A, Buřič M. 2020. Pilferer, murderer of innocents or prey? The potential impact of killer shrimp (Dikerogammarus villosus) on crayfish. Aquatic Sciences 83(1): 5. https://doi.org/10.1007/s00027-020-00762-8


Freshwater ecosystems worldwide are facing the establishment of non-native species, which, in certain cases, exhibit invasive characteristics. The impacts of invaders on native communities are often detrimental, yet, the number and spread of non-native invasive species is increasing. This is resulting in novel and often unexpected combinations of non-native and native species in natural communities. While the impact of invaders on native species is increasingly well-documented, the interactions of non-native invaders with other non-native invaders are less studied. We assessed the potential of an invasive amphipod, the killer shrimp Dikerogammarus villosus (Sowinsky, 1894), to cope with other established invaders in European waters: North American crayfish of the Astacidae family—represented by signal crayfish Pacifastacus leniusculus (Dana, 1852), and the Cambaridae family—represented by marbled crayfish Procambarus virginalis Lyko, 2017. The main goal of this study was to investigate if killer shrimp, besides their role as prey of crayfish, can significantly influence their stocks by predating upon their eggs, hatchlings and free-moving early juveniles. Our results confirmed that killer shrimp can predate on crayfish eggs and hatchlings even directly from females abdomens where they are incubated and protected. As marbled crayfish have smaller and thinner egg shells as well as smaller juveniles than signal crayfish, they were more predated upon by killer shrimp than were signal crayfish. These results confirmed that the invasive killer shrimp can feed on different developmental stages of larger freshwater crustaceans and possibly other aquatic organisms.

Keywords: freshwater • Crustacea • amphipod • invasive species • interaction • predation

Open access

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