31 October 2020

Marmorkrebs map update

I am experimenting with a change to the map of Marmorkrebs introductions. A new paper (Son et al. 2020) describes a location where Marmorkrebs seem to have been eradicated with some certainty.


One of the first recorded localities of P. virginalis — a cascade of ornamental ponds in Odesa, where three live individuals were observed in June 2015 — was also surveyed. Shortly after that discovery, those reservoirs underwent multi-stage cleaning and renovation. During the winter-spring period of 2017–2018, a consistent complete drying of all ponds was carried out. In the course of those activities, large animals such as fish and turtles, including invasive red-eared sliders Trachemys scripta (Schoepff, 1792), were placed in aquariums and released back later. Conversely, soft sediment accumulated at the bottom along with benthic invertebrates was removed from these water bodies. As a result, we can confidently assert that P. virginalis was eradicated in that locality.


Günter Vogt emailed me to say that there are no known active populations in Sweden or the Netherlands.


I have added a new symbol to the map: a vertical line on top of a horizontal line. This is a symbol used in Japanese maps to indicate a graveyard. I am aware that maps like this sometimes can solidify hypotheses or tentative claims into “fact,” so I am not sure right now what criteria to use for adding an “removed” symbol to the map.


The map is, as always, a work in progress.




Son MO, Morhun H, Novitskyi RO, Sidorovskyi S, Kulyk M, Utevsky S. 2020. Occurrence of two exotic decapods, Macrobrachium nipponense (de Haan, 1849) and Procambarus virginalis Lyko, 2017, in Ukrainian waters. Knowledge and Management of Aquatic Ecosystems 421: 40. https://doi.org/10.1051/kmae/2020032

Son and colleagues, 2020

Knowledge and Management of Aquatic Ecosystems coverSon MO, Morhun H, Novitskyi RO, Sidorovskyi S, Kulyk M, Utevsky S. 2020. Occurrence of two exotic decapods, Macrobrachium nipponense (de Haan, 1849) and Procambarus virginalis Lyko, 2017, in Ukrainian waters. Knowledge and Management of Aquatic Ecosystems 421: 40. https://doi.org/10.1051/kmae/2020032




New information on the occurrence of two alien decapod crustaceans, Macrobrachium nipponense and Procambarus virginalis, was summarized for Ukraine. The invasive potential of both species was estimated in the context of local environmental and socio-economic issues. Their history as non-native species is marked by the early use of alien decapods as a natural resource by local residents. Both intentional and unintentional introductions occurred for M. nipponense, while the ornamental trade was an important source of non-native P. virginalis. New records of M. nipponense and P. virginalis from open freshwater habitats in the Odesa and Kharkiv provinces suggest continuing expansion of these decapods. We conducted a molecular phylogenetic analysis of COI sequences, which confirmed morphological identifications of invasive M. nipponense. This reinforces the presumed pathway of this species, including its pathway from China to south-western Ukraine. Procambarus fallax was found to be paraphyletic in relation to P. virginalis, which was probably caused by analyzing only one mitochondrial gene, which could be impacted by the recent emergence of the latter species.


Keywords: Decapoda • Macrobrachium nipponenseProcambarus virginalis • Ukraine • invasive species



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 Kalinkat 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.


Additional, 25 October 2020: The story has made it into a US newspaper. Weirdly, they chose to illustrate the story with what appears to be a signal crayfish (Pacifastacus leniusculus) instead of Marmorkrebs.


External links


Hundreds of self-cloning crayfish invade Antwerp cemetery


Escaped cloned female mutant crayfish take over Belgian cemetery


Self-cloning mutant crayfish take over Belgian cemetery


Mutant crayfish clones take over cemetery after aquarium escape


Self-cloning mutant crayfish are invading a Belgian cemetery


Self-cloning mutant crayfish are invading a Belgian cemetery and will wreak havoc on the local biodiversity if not controlled, expert warns


Honderden rivierkreeften in slotgrachten Schoonselhof (With video clip)


What are marbled crayfish? Know everything about these dangerous species invading in Belgium


Self-cloning crayfish have taken over a cemetery in Belgium


Belgium: Self-cloning mutant crayfish invade historic cemetery, scientists concerned


Hundreds of self-cloning mutant crayfish invade cemetery in Belgium. 2020 isn't over yet

Maagdelijke kreeft op Antwerpse begraafplaats (roughly translated, “Virgin crayfish in Antwerp 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