22 June 2018

Vogt, 2018

Vogt G. 2018. Glair glands and spawning in unmated crayfish: a comparison between gonochoristic slough crayfish and parthenogenetic marbled crayfish. Invertebrate Zoology 15(2): 215–220. https://doi.org/10.15298/invertzool.15.2.02, http://kmkjournals.com/journals/Inv_Zool/IZ_Index_Volumes/IZ_15/IZ_15_2_215_220_Vogt


In the period before spawning, freshwater crayfish females develop glair glands on the underside of the pleon. These glands produce the mucus for a gelatinous tentlike structure in which the eggs are fertilized and attached to the pleopods. Long-term observation of females of the sexually reproducing slough crayfish, Procambarus fallax, kept in captivity revealed that the glair glands developed in late winter and late summer of each year independently of the presence of males. In mated females, they secreted their contents shortly before spawning. In contrast, unmated females of slough crayfish did
neither empty their glair glands nor spawn. Their glands persisted for an unusually long period of time and disappeared only during the next moult. Apparently, slough crayfish females use information on sperm availability to either spawn or save the resources. Females of marbled crayfish, Procambarus virginalis, a parthenogenetic all-female descendant of slough crayfish, developed glair glands in approximately the same periods of the year but generally spawned despite of the lack of males. These findings suggest that in marbled crayfish glair secretion and spawning is decoupled from mating. Therefore, the species pair P. fallax and P. virginalis seems to be particularly suitable to investigate the regulation of spawning in freshwater crayfish.

Keywords: freshwater crayfish • glair gland • spawning • mating • Procambarus fallaxProcambarus virginalis

Zoo babies

Marbled crayfish are featured in this year’s Cincinnati Zoo’s Zoo Babies display! The Zoo’s website shows they are part of the display, but no more. I do complement their photographer for the particularly cute crayfish pic (above) on their site.

I reached out to the Zoo, and heard back from Mandy Pritchard, who is the “World of the Insect Team Leader” at the zoo. (Now there’s a great job title.) She was kind enough to send me a couple of pictures of the display:

There’s a very nice shirt available. Unfortunately, it’s doesn’t seem to be available in adult sizes.

Based on the description in the display, I think these are the sexual slough crayfish and not Marmorkrebs. But it’s fun to see crayfish on display nevertheless!

External links

Zoo Babies
The "Amazing" Marbled Crayfish - Youth Garments

19 June 2018

Herrmann and colleagues, 2018

Herrmann A, Schnabler A, Martens A. 2018. Phenology of overland dispersal in the invasive crayfish Faxonius immunis (Hagen) at the Upper Rhine River area. Knowledge and Management of Aquatic Ecosystems 419: 30. https://doi.org/10.1051/kmae/2018018


The non-indigenous crayfish Faxonius immunis (Hagen) is the dominant crayfish species at the Upper Rhine River system since his detection in 1993. As an invasive alien species, it is one of the biggest threats to aquatic biodiversity in the area. By dispersing over land, the species has a high potential to colonize small ponds created for threatened amphibians and dragonflies. Shortly after invasion, the fast growing population of F. immunis is changing the habitat drastically. In June 2016, our team started a local information campaign including citizen science project where the local people south of Karlsruhe, Baden-Wuerttemberg, Germany, could contact us when they spot a crayfish migrating over land to assess the activity of overland dispersal on a regional scale. Until January 2018, we got a total of 98 responses. Thirty-nine include suitable information including 33 records of overland dispersal of F. immunis. The species was recorded on land throughout the year, except February and July. Additionally, single observations of overland dispersal of other invasive crayfish species, naming Procambarus clarkii (Girard), Pacifastacus leniusculus (Dana), Procambarus virginalis (Lyko) and Faxonius limosus (Rafinesque), were recorded.

Keywords: amphibian conservation • citizen science • management • biological invasions • non-indigenous species

08 June 2018

If this is 2018, this must be Estonia

Estonia has now become the...

Wait a second, I’ve lost count.

  1. Germany.
  2. Italy.
  3. Netherlands.
  4. Hungary.
  5. Croatia.
  6. Slovakia.
  7. Romania.
  8. Sweden.
  9. Ukraine.
  10. Czech Republic.
  11. ...
Eleventh European country where Marmorkrebs have been found in outdoors. This is according to a press release from the Estonian Research Council. The crayfish were collected last year, not recognized as Marmorkrebs until the end of the year, and a repeat visit at the end of May confirmed a population was there.

I have updated the map of Marmorkrebs introductions accordingly.

External links

The marbled crayfish have established themselves in Narva power plant

30 May 2018

Scholz and colleagues, 2018

Scholz S, Richter S, Wirkner CS. 2018. Constant morphological patterns in the hemolymph vascular system of crayfish (Crustacea, Decapoda). Arthropod Structure & Development 47(3): 248-267. https://doi.org/10.1016/j.asd.2017.12.005


We present a study of the hemolymph vascular system of the marbled crayfish, Procambarus fallax f. virginalis, the only crayfish species known to be parthenogenetic. To identify potential evolutionary patterns, we compared data from a total of 48 specimens of P. fallax with 22 specimens of Orconectes limosus. Visualizations (2D and 3D) were carried out using a combination of classical and modern morphological techniques. Our data were compared to the existing literature. Like all Decapoda, both P. fallax and O. limosus have a hemolymph vascular system, consisting of a globular heart with seven off-branching arteries. We were able to visualize in detail the heart of crayfish for the first time, i.e., the heart muscle itself, with its loose bundles of myofibrils, as well as the valves and flaps of ostia and arteries. Furthermore, the branching patterns of the seven artery systems were analyzed. Anatomical structures identified to be consistent in all specimen of both species were combined, and a proposed schematic anatomy established of the hemolymph vascular system of crayfish.

Keywords: artery • circulatory system • evolutionary morphology • heart

Nentwig and colleagues, 2018

Nentwig W, Bacher S, Kumschick S, Pyšek P, Vilà M. 2018. More than “100 worst” alien species in Europe. Biological Invasions 20(6): 1611–1621. https://doi.org/10.1007/s10530-017-1651-6


“One hundred worst” lists of alien species of the greatest concern proved useful for raising awareness of the risks and impacts of biological invasions amongst the general public, politicians and stakeholders. All lists so far have been based on expert opinion and primarily aimed at representativeness of the taxonomic and habitat diversity rather than at quantifying the harm the alien species cause. We used the generic impact scoring system (GISS) to rank 486 alien species established in Europe from a wide range of taxonomic groups to identify those with the highest environmental and socioeconomic impact. GISS assigns 12 categories of impact, each quantified on a scale from 0 (no impact detectable) to 5 (the highest impact possible). We ranked species by their total sum of scores and by the number of the highest impact scores. We also compared the listing based on GISS with other expert-based lists of the “worst” invaders. We propose a list of 149 alien species, comprising 54 plants, 49 invertebrates, 40 vertebrates and 6 fungi. Among the highest ranking species are one bird (Branta canadensis), four mammals (Rattus norvegicus, Ondatra zibethicus, Cervus nippon, Muntiacus reevesi), one crayfish (Procambarus clarkii), one mite (Varroa destructor), and four plants (Acacia dealbata, Lantana camara, Pueraria lobata, Eichhornia crassipes). In contrast to other existing expert-based “worst” lists, the GISS-based list given here highlights some alien species with high impacts that are not represented on any other list. The GISS provides an objective and transparent method to aid prioritization of alien species for management according to their impacts, applicable across taxa and habitats. Our ranking can also be used for justifying inclusion on lists such as the alien species of Union concern of the European Commission, and to fulfil Aichi target 9.

Keywords: Aichi target 9 • environmental impacts • generic impact scoring system (GISS) • prioritization of alien species • risk assessment • socio-economic impacts

23 May 2018

Rymut, 2018

Rymut, JA. 2018.Determining the effects of nitric oxide on Procambarus fallax forma virginalis. Poster given at the International Crustacean Congress IX, Washington DC, USA, 22-25 May 2018. http://www.birenheide.com/ICC2018/program/singlesession.php3?sessid=P, poster P.33.


Ethanol (EtOH) effects inducible nitric oxide synthase (iNOS) activity by inhibiting the production of iNOS in cells. Acute doses increase the production of nitric oxide (NO) and endothelial NOS (eNOS). At higher dosages, ethanol impairs endothelial functions. NO has been found to suppress the feeding response in pond snails, Lymnaea stagnalis, induce synaptic depression in crayfish, and inhibit the swimming rhythm of Xeonpus laevis tadpoles. This in vivo study will be performed in order to determine if synaptic depression is caused by free radical NO and determine if overall movements are decreased in Procambarus forma fallax virginalis (P.f.f virginalis) in the presence of NO. It was hypothesized that there will be a depression in synaptic activity and less movement in crayfish exposed to free radical NO. A probe will be inserted near the cerebral ganglion to assess depression in synaptic inputs. Movement will be tested by placing crayfish into a partitioned tank and counting each movement across a partition as one movement. Movement will be tested on both an individual and group level to determine if group activity will be a variable factor. NO will be introduced through the usage of ethanol, an L-arginine supplement, and chlorhexidine​ in an approximate range of five to ten​ parts per million (​5 ​mg/L​ and 10 mg/L​).

Keywords: None provided.

Update, 30 May 2018: At the author’s request, here is the updated abstract from the poster as it was presented at the meeting (above).

Ethanol (Et-OH) effects inducible nitric oxide synthase (iNOS) activity by inhibiting the production of iNOS in cells. Acute doses increase the production of nitric oxide (NO) and endothelial NOS (eNOS). At higher dosages, ethanol impairs endothelial functions. NO has been found to suppress the feeding response in pond snails, Lymnaea stagnalis, induce synaptic depression in crayfish, and inhibit the swimming rhythm of Xenopus laevis tadpoles (Aonuma, et al. 2000). This in vivo study has been performed in order to determine if synaptic depression is caused by NO, and if overall movements are decreased in Procambarus forma fallax virginalis (P.f.f virginalis) and Procambarus blandingii, in the presence of NO. Movement was assessed in a labeled gridded tanks of water, denatured ethanol (3 ppm), L-arginine (Reagent grade, 1ppb) and chlorhexidine (99.95%, 1ppb). There was an evident trend over a time interval of 6 minutes ≤ t ≤ 8 minutes, where the control, ethanol and chlorhexidine all had a stark drop off in activity, whilst L-arginine had a stark increase. It is hypothesized that this could be due to a metabolic pathway of L-arginine is converted through nitric oxide synthase (NOS) to L-citrulline (Racke, et al. 2010); whereas ethanol has proven to inhibit iNOS, and due to the cytostatic characteristics of chlorhexidine, it can be assumed that the correlation of chlorhexidine to ethanol lies in this pathway as well. Synaptic depression is shown where L-arginine is present, over a time interval of 0 ms ≤ t ≤ 10ms (Aonuma et al. 2010); as found in the study, there is a correlation between L-arginine and chlorhexidine pre-wash, and it is hypothesized that this is from the terminal guanylyl group.

16 May 2018

Faulkes and colleagues, 2018

Faulkes Z, DeLeon H, Thomas J. 2018. Cloning crayfish cell culture. Poster presentation given at the International Crustacean Congress IX, 22-25 May 2018, Washington, DC, USA. http://www.birenheide.com/ICC2018/program/singlesession.php3?sessid=P, poster P.81.


The parthenogenetic marbled crayfish, Marmorkrebs, is an emerging model organism. For example, it is the only decapod crustacean with a sequenced genome, and several labs have used Marmorkrebs as a model for embryonic development. One difficulty in studying embryonic cells is that eggs contain a large amount of yolk, which can make imaging embryonic cells difficult. We successfully isolated and cultured cells from early stage Marmorkrebs embryos, and confirmed their identity using DNA sequencing. Cellular and molecular tools for use in crayfish are underdeveloped compared to other model organisms, and cultured embryonic cells could provide a new testbed for those techniques.

Keywords: None provided.

09 May 2018

Vogt, 2018b

Vogt G. 2018. Annotated bibliography of the parthenogenetic marbled crayfish Procambarus virginalis, a new research model, potent invader and popular pet. Zootaxa 4418(4): 301-352. https://doi.org/10.11646/zootaxa.4418.4.1


The marbled crayfish Procambarus virginalis is a new obligately parthenogenetic species that was detected in the mid-1990s in the German aquarium trade. Since then it has become a popular pet in many countries throughout the world and a valuable laboratory model for a broad range of biological disciplines. Releases have led to the establishment of wild
populations in several European countries, Madagascar and probably Japan, making marbled crayfish an interesting paradigm of evolutionarily young and ongoing bioinvasions. This article provides an annotated bibliography of the scientific and popular scientific literature on marbled crayfish from its detection until today. Each reference is assigned to a publication format and one or more biological categories. The content is shortly described and its significance for marbled crayfish research and general biology is assessed. Of the 239 references listed 140 (58.6%) deal primarily with laboratory experiments on the biology of marbled crayfish and the establishment and use of marbled crayfish as a research model, 74 (31.0%) with its biogeography, invasions and ecology and 25 (10.4%) with hobby aquarist issues and the pet trade.

Keywords: Crustacea • Decapoda • development • ecology • genetics • morphology • neurobiology • physiology • speciation • stem cell biology • toxicology

08 May 2018

Zeng and Yeo, 2018

Zeng Y, Yeo DCJ. 2018. Assessing the aggregated risk of invasive crayfish and climate change to freshwater crabs: A Southeast Asian case study. Biological Conservation 223: 58-67. https://doi.org/10.1016/j.biocon.2018.04.033


Primary freshwater crabs represent a culturally and ecologically significant component of freshwater habitats globally that has a high percentage of threatened species. Invasive species (especially non-indigenous crayfish) and climate change are not only important standalone threats, but are also expected to compound existing threats (e.g., habitat loss/modification, pollution) and challenge the long-term survival of these decapod crustaceans. This study illustrates the importance of considering these two emerging and growing threats in conservation or management strategies by quantifying (via species distribution models) the individual and aggregated risks of these threats in Southeast Asia, a region with the highest diversity of primary freshwater crabs and a high proportion of imperiled species. Results predicted that most species of crabs (82.1%) will co-occur (and hence interact) with invasive crayfish to a moderate to high degree, and most species (69.2%) will also experience a reduction in suitable climate conditions in the future. In terms of aggregated risk, the results also predict an increased overlap between invasive crayfish and native crabs for three out of the seven species analyzed (namely Procambarus virginalis, Cherax destructor and Orconectes rusticus). Findings from this study provide a quantitatively derived rationale for the development of adaptive regulations and conservation plans in the region to minimize the risk of invasive species in a cost-effective way, thereby enabling the protection of Southeast Asia's natural heritage and its vital ecosystem services.

Keywords: alien species • Cherax • environmental niche model • non-indigenous species • Procambarus • radiative forcing target levels • species distribution model

Oleh and colleagues, 2018

Oleh M, Kyrylo B, Olena K. 2018. Biological and biomechanical principles of the controlling molluscs Melanoides tuberculata (Müller 1774) and Tarebia granifera (Lamarck, 1822) in reservoirs of strategic importance World Scientific News 99: 71-83. http://www.worldscientificnews.com/wp-content/uploads/2018/04/WSN-99-2018-71-83.pdf


The article presents the results of complex laboratory investigations on the biological and biomechanical ways of control of Melanoides tuberculata (Müller 1774) and Tarebia granifera (Lamarck, 1822) molluscs in simulated conditions close to the conditions of the cooling pond of the Zaporizhia Nuclear Power Plant. It was determined that molluscs have naturalized in the Zaporizhia Nuclear Power Plant cooling pond, quickly increased their number and created a threat to hydraulic structures. Taking into account biological features of Thiaridae mollusks and technical and ecological features of Zaporizhia NPP, we carried out a series of experiments using biological control measures (the use of predatory species of hydrobionts) and mechanical means for controlling mollusks. Representatives of different taxons of the Animalia Kingdom were selected as predatory species of hydrobionts, which potentially can consume gastropods: Mollusca, Crustaceans and Fish. It has been found experimentally that the use of marbled crayfish Procambarus virginalis (Lyko, 2017), pumpkinseed Lepomis gibbosus (Linnaeus, 1758) and Botia lohachata Chaudhuri, 1912 has not given positive results in the development of measures to control the number of molluscs. Positive results were obtained in a series of experiments with predatory mollusc assassin snail Clea helena (von dem Busch, 1847), but it was noted that in the presence of more accessible feeds, assassin snail Clea helena (von dem Busch, 1847) consumes smaller quantities of Thiaridae mollusks. The most successful results we obtained in experiments with traps for molluscs. We have developed experimental constructions of traps with lower and upper inlets that act as mollusk accumulator and can be installed in the coastal zone of the reservoir and Zaporizhia NPP cooling system channels for reducing the number of reproductive individuals of Melanoides tuberculata (Müller 1774) and Tarebia granifera (Lamarck, 1822). The most effective were the traps with the lower inlet to which the mollusks could get faster. In order to attract mollusks to traps, we have conducted studies on the use of feed baits for molluscs. Most effectively, molluscs fell into traps that contained lime feed, feedstock sunflower oil and anise oil. The most effective among mollusks was the bait with the addition of anise oil. During the exposure, traps with anise bait traps accumulated 14.1% of molluscs. The conducted researches can serve as the basis for the development of biomelioration measures aimed at reducing the negative impact of accidental introduction of new species of molluscs into technical reservoirs of strategic importance.

Keywords: Clea helenaMelanoides tuberculataTarebia granifera • Zaporizhia Nuclear Power Plant • assassin snail • biological invasion • cooling pond • red-rimmed melania • thiarids

28 April 2018

Allo or auto? Betting on Marmorkrebs origins

Picture of Bugatti car with text, 'Why not hybrid?'

In a new article in PNAS, James Mallet writes:

An extraordinary recent case is the marbled crayfish Procambarus virginalis, which seems to have originated via a hybrid between two North American Procambarus species and was likely spread via the pet trade. The marbled crayfish is a triploid hybrid, very likely created in captivity, and is entirely parthenogenetic. After escaping from captivity, it has since spread to become invasive in many European countries as well as in Madagascar.

Mallet cites Gutekunst and colleagues (2018) to support this. But they specifically said, “We do not think Marmorkrebs is a hybrid.”

Alternative hypotheses involving allopolyploid formation with P. alleni appear unlikely due to the lack of hybrid morphological features and the considerable genetic differences.

And it’s not just them. Vogt and colleagues (2016) wrote:

The morphological features and microsatellite patterns strongly suggest that marbled crayfish originated by autopolyploidisation and not by hybridisation with a closely related species, which is by far the most frequent cause of triploidy in animals.

There is some overlap in the author lists of Gutekunst et al. (2018) and Vogt et al. (2016). Having the some of the same authors makes it not surprising that the two papers reach the same conclusions. But they are not the only ones. Martin and colleagues (2016) reached the same conclusion:

Martin et al. (2010) suggested that the Marmorkrebs originated directly from sexual P. fallax without hybridization.

Our data tentatively support this conclusion. Based on the assumption of a hybridization between P. fallax and P. alleni, one would expect that the numerically different karyotypes of these two species would have led to a chromosome number higher than that counted in Marmorkrebs. Furthermore, a preliminary comparison of the nuclear protein coding histone H3 gene (H3) and the nuclear elongation factor 2 gene (EF-2) revealed at least seven polymorphic positions within the EF-2 intron that suggest a non-hybrid origin of the Marmorkrebs.

For a very long time, I would have bet money that Marmorkrebs was a hybrid, because so many cases of asexual reproduction trace back to hybridization events. All of the papers above go on to say that, strictly speaking, there is still a very slight possibility that Marmorkrebs is a hybrid. But hybridization isn’t the way to bet any more.


Gutekunst J, Andriantsoa R, Falckenhayn C, Hanna K, Stein W, Rasamy J, Lyko F. 2018. Clonal genome evolution and rapid invasive spread of the marbled crayfish. Nature Ecology & Evolution 2(3): 567–573. https://doi.org/10.1038/s41559-018-0467-9

Mallet J. 2018. Invasive insect hybridizes with local pests. Proceedings of the National Academy of Sciences: in press. https://doi.org/10.1073/pnas.1804081115

Martin P, Thonagel S, Scholtz G. 2016. The parthenogenetic Marmorkrebs (Malacostraca: Decapoda: Cambaridae) is a triploid organism. Journal of Zoological Systematics and Evolutionary Research 54(1): 13-21. http://dx.doi.org/10.1111/jzs.12114

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

10 April 2018

Maughan, 2018

Maughan M. 2018. Cyclical parthenogenesis in crustaceans. Poster presentation, Utah State University, 12 April 2018. https://digitalcommons.usu.edu/researchweek/ResearchWeek2018/All2018/283/


Apomixis is the replacement of sexual reproduction with asexual reproduction in plants. Some scientists hypothesize that apomixis is caused by genetics that evolved after sexual reproduction and apomixis mutated from sexual reproduction. However, we hypothesize that sexual reproduction and apomixis evolved simultaneously during eukaryogenesis, the evolution of eukaryotic life. We think that most organisms retain the capacity for apomixis and sexual reproduction in their genome. Many taxa, including plants and crustaceans, should have a single genome able to express both sexual and asexual reproduction as long as the correct metabolic signaling is provided to the germline cells. In Professor John Carman’s lab, researchers have successfully induced onset of apomixia in sexual plants. These successes support our hypothesis and suggest that some animals could also have the pathogenesis and sexual reproduction capabilities in their genome. The equivalent of plant apomixis in animals is apomictic parthenogenesis. We focus on cyclical parthenogenesis. In cyclical parthenogenesis animals alternate between sexual and asexual reproduction. Daphnia magna and Procambarus virginalis (marbled crayfish) are both cyclically parthenogenetic. The TOR (rapamycin complex 1) signaling pathway in plants and animals is a regulator of cell growth and it affects the pathway of reproduction. Oxidative stress turns off the TOR signaling pathway and turns SnRK1(SNF1-related kinase 1 in yeast and AMPK in animals) on. SnRK1 makes cells begin the process of sexual reproduction. To test this hypothesis, I will be researching how to switch asexual organisms to reproduce sexually. I will inject the ovaries of crayfish with chemicals designed to alter their glucose levels and place the Daphnia in a solution containing the appropriate chemicals. The presence of an egg sack from the Daphnia and the presence of male crayfish will show the success of the expirement (sic).

Keywords: None provided.

02 April 2018

Neff, 2018

Neff EP. 2018. The Marmorkrebs model. Lab Animal 47(4): 107-107. https://doi.org/10.1038/s41684-018-0030-y


Without abstract. First paragraph:

In his lab at the German Cancer Research Center in Heidelberg, Frank Lyko studies epigenetics, how the environment can change an organism’s phenotype without altering its underlying DNA. About 15 years ago, a colleague introduced him to the marbled crayfish, a triploid, clonal, parthenogenic, and only very recently speciated invertebrate that’s proven to be quite the invasive pest across the globe. At the time, the Marmorkrebs (as it’s known in German) didn’t register in Lyko’s research plans. But recently, he began thinking about alternative models. Classical laboratory animals, like mice, worms, and fruit flies, “always have the same phenotype, and if you induce a genetic mutation you get one aberrant phenotype normally,” he explains. “This is super helpful if you do genetic research but it’s not necessarily good for describing what’s going on in epigenetics.” He tried honeybees, but found them challenging to keep in the laboratory. His lab wasn’t fond of another potential epigenetic model, the African desert locust, either. “These were really big animals and they were always escaping and flying around, so that was a mess,” he recalls. “Then I remembered my old conversation with Günter Vogt.”

Keywords: None provided.

30 March 2018

Why people can’t take invasive crayfish seriously

In compiling the news coverage and reactions to the Marmorkrebs genome sequence (which is still trickling in), I’ve noticed a common reaction. The story describes Marmorkrebs as an invasive, outlines the problem, and someone shows up in the comments saying something like, “Mmmm. Gumbo!” or “Get the melted butter ready,” or something like that.

Jokes like that show pretty clearly that people think invasive crayfish are a joke, and nothing to worry about. And as much as I love the Non Sequiter cartoon about Marmorkrebs, it also uses the problem for comedy.

“Eat them all” is not an attitude unique to North America:

This novel perspective on invasive species was perhaps most elegantly stated as we made small talk with a taxi driver in Wuhan. As we explained our research through an interpreter, the taxi driver smiled and asked, “Can they really be considered a problem if people eat them?”

This attitude is perhaps more understandable in China, given that “Chinese food” in China means “crayfish” more than General Tso’s chicken. Louisiana red swamp crayfish are the most popular restaurant dish, and that makes for a $22 billion (yes, with a “B”) market.

But there are at least two problems with the “We can eat them” attitude. First, people don’t understand that there are differences in commercial viability. Marmorkrebs are small compared to Louisiana red swamp crayfish, meaning that you are expending more effort for less meat. It’s like saying, “Hey, Asian carp are fish, we can eat fish, no problem,” without realizing that they’re bony, and not many people want to eat carp. (This may not be an insurmountable problem, though.)

Similarly, not everyone wants to eat crayfish. My understanding that in some places, suggesting that people eat crayfish goes over about as well as suggesting people in the United States eat cockroaches.

But the other problem is that while it sounds good in theory, there’s not a lot of evidence that introducing commercial harvest for invasives will get rid of the problem. Barbour and colleagues (2011) looked at the prospect of controlling lionfish by fishing them for food. They concluded:

(C)omplete eradication of lionfish through fishing is unlikely, and substantial reduction of adult abundance will require a long-term commitment and may be feasible only in small, localized areas where annual exploitation can be intense over multiple consecutive years.

A later paper (de Leon and colleagues, 2013) reached similar conclusions:

While removal efforts are effective at reducing the local number of lionfish, recruitment from unfished locations, such as those too deep for recreational diving and at dive sites that are difficult to access, will continuously offset the effects of removal efforts.

Still, some are continuing to investigate this for lionfish (Chapman et al. 2016).

Indeed, creating commerical fisheries for aquatic invasives probably increases the problems, since you now have incentives to perform even more introductions (Nuñez and colleagues, 2012; Pasko and Goldberg 2014), even through the track record is poor. Establishing commericial fisheries for crayfish was one of the main reason North American species were introduced in many European countries decades ago (e.g., Sweden), and they have since realized that they are causing far more problems than they made money.

If we are going to stop introductions of non-native crayfish, we are going to have to convince people that the problem is serious. Jokes about food show they aren’t there yet.


Barbour AB, Allen MS, Frazer TK, Sherman KD. 2011. Evaluating the potential efficacy of invasive lionfish (Pterois volitans) removals. PLOS ONE 6(5): e19666. https://doi.org/10.1371%2Fjournal.pone.0019666

Chapman JK, Anderson LG, Gough CLA, Harris AR. 2016. Working up an appetite for lionfish: A market-based approach to manage the invasion of Pterois volitans in Belize. Marine Policy 73: 256-262. http://www.sciencedirect.com/science/article/pii/S0308597X16304857

de León R, Vane K, Bertuol P, Chamberland VC, Simal F, Imms E, Vermeij MJA. 2013. Effectiveness of lionfish removal efforts in the southern Caribbean. Endangered Species Research 22(2): 175-182. http://www.int-res.com/abstracts/esr/v22/n2/p175-182/

Nuñez MA, Kuebbing S, Dimarco RD, Simberloff D. 2012. Invasive species: to eat or not to eat, that is the question. Conservation Letters 5(5): 334-341. https://doi.org/10.1111/j.1755-263X.2012.00250.x

Pasko S, Goldberg J. 2014. Review of harvest incentives to control invasive species. Management of Biological Invasions 5(3): 263–277. https://doi.org/10.3391/mbi.2014.5.3.10

Related posts

Marmorkrebs genome news round-up

External links

Louisiana crayfish: good, bad, and delicious
The economy of crayfish
Non Sequiter cartoon: Crayfish apocalypse
Eat The Enemy: The Delicious Solution To Menacing Asian Carp

Picture from here.

26 March 2018

The crayfish apocalypse

Of over a hundred news articles, blog posts, and other miscellaneous things I have seen on the Internet about Marmorkrebs since the genome paper came out, this Non Sequiter comic by Wiley may be my favourite of all of them. And that includes articles that quoted me or used my Marmrorkrebs picture.

Click here to read it.

Hat tip to James Murray.

22 February 2018

Gutekunst and colleagues, 2018

Gutekunst J, Andriantsoa R, Falckenhayn C, Hanna K, Stein W, Rasamy J, Lyko F. 2018. Clonal genome evolution and rapid invasive spread of the marbled crayfish. Nature Ecology and Evolution 2(3): 567–573. https://doi.org/10.1038/s41559-018-0467-9


The marbled crayfish Procambarus virginalis is a unique freshwater crayfish characterized by very recent speciation and parthenogenetic reproduction. Marbled crayfish also represent an emerging invasive species and have formed wild populations in diverse freshwater habitats. However, our understanding of marbled crayfish biology, evolution and invasive spread has been hampered by the lack of freshwater crayfish genome sequences. We have now established a de novo draft assembly of the marbled crayfish genome. We determined the genome size at approximately 3.5 gigabase pairs and identified > 21,000 genes. Further analysis confirmed the close relationship to the genome of the slough crayfish, Procambarus fallax, and also established a triploid AA’B genotype with a high level of heterozygosity. Systematic fieldwork and genotyping demonstrated the rapid expansion of marbled crayfish on Madagascar and established the marbled crayfish as a potent invader of freshwater ecosystems. Furthermore, comparative whole-genome sequencing demonstrated the clonality of the population and their genetic identity with the oldest known stock from the German aquarium trade. Our study closes an important gap in the phylogenetic analysis of animal genomes and uncovers the unique evolutionary history of an emerging invasive species.

Keywords: comparative genomics • evolutionary genetics • invasive species

Vogt, 2018

Vogt G. 2018. Investigating the genetic and epigenetic basis of big biological questions with the parthenogenetic marbled crayfish: A review and perspectives. Journal of Biosciences 43(1): 189-223. https://doi.org/10.1007/s12038-018-9741-x


In the last 15 years, considerable attempts have been undertaken to develop the obligately parthenogenetic marbled crayfish Procambarus virginalis as a new model in biology. Its main advantage is the production of large numbers of offspring that are genetically identical to the mother, making this crustacean particularly suitable for research in epigenetics. Now, a draft genome, transcriptome and genome-wide methylome are available opening new windows for research. In this article, I summarize the biological advantages and genomic and epigenetic features of marbled crayfish and, based on first promising data, discuss what this new model could contribute to answering of “big” biological questions. Genome mining is expected to reveal new insights into the genetic specificities of decapod crustaceans, the genetic basis of arthropod reproduction, moulting and immunity, and more general topics such as the genetic underpinning of adaptation to fresh water, omnivory, biomineralization, sexual system change, behavioural variation, clonal genome evolution, and resistance to cancer. Epigenetic investigations with the marbled crayfish can help clarifying the role of epigenetic mechanisms in gene regulation, tissue specification, adult stem cell regulation, cell ageing, organ regeneration and disease susceptibility. Marbled crayfish is further suitable to elucidate the relationship between genetic and epigenetic variation, the transgenerational inheritance of epigenetic signatures and the contribution of epigenetic phenotype variation to the establishment of social hierarchies, environmental adaptation and speciation. These issues can be tackled by experiments with highly standardized laboratory lineages, comparison of differently adapted wild populations and the generation of genetically and epigenetically edited strains.

Keywords: cancer resistance • disease susceptibility • DNA methylation • environmental adaptation • epigenetics • genomics • immunity • marbled crayfish • regeneration • speciation

17 February 2018

Marenkov and colleagues, 2017

Marenkov O, Holoborodko K, Voronkova Y, Gorban V. 2017. Effect of zinc and cadmium ions on histostructure of antennal glands of marbled crayfish Procambarus fallax (Hagen, 1870) f. virginalis (Decapoda). Acta Biologica Universitatis Daugavpiliensis 17(2): 219–224. http://sciences.lv/wp-content/uploads/2018/01/Marenkov.pdf


Research results about the effects of cadmium and zinc ions on the histological structure of cells of antennal glands of marbled crayfish Procambarus fallax (Hagen, 1870) f. virginalis
(Decapoda) are presented in the article. It is determined that size of glandulocytes and their nuclei affected by to heavy metals naturally reduces however nuclear-cytoplasmic ratio is stably preserved, which is probably the excretory system adaptive response to the impact of heavy metals ions.

Keywords: cadmium • zinc • marbled crayfish • glandulocytes • Procambarus fallax (Hagen, 1870) f. virginalis

06 February 2018

Global Register of Introduced and Invasive Species

Pagad and colleagues (2018) have a new paper about the Global Register of Introduced and Invasive Species. Naturally, I went looking for Marmorkrebs.

The first interesting thing is that Marmorkrebs appeared in the database with four different species name variations:

  • Procambarus fallax (incomplete)
  • Procambarus fallax f virginalis (missing period)
  • Procambarus fallax f. virginalis (correct)
  • Procambarus fallaxformvirginalis (even if spaces were added, would be wrong: “form” should be “forma”)

You can’t search for common names, for the looks of things, just Latin ones. We will have to wait and see whether the proposal to change the name of Marmorkrebs to Procambarus virginalis will reduce the number of variations in lists like these, or just be one more variant to search for.

The second interesting thing is that are only four countries on the list: Germany, Sweden, Croatia, Ukraine. The map of Marmorkrebs introductions that I curate has six more: Madagascar, Japan, Italy, Hungary, the Czech Republic, Slovakia, and the Netherlands. It will be interesting to check in from time to time to see how long it takes for this to be updated.


Pagad S, Genovesi P, Carnevali L, Schigel D, McGeoch MA. Introducing the Global Register of Introduced and Invasive Species. Scientific Data

External links

Global Register of Introduced and Invasive Species 5: 170202. https://doi.org/10.1038/sdata.2017.202

05 February 2018

Marmorkrebs genome news round-up

The first crayfish genome is done, and it’s Marmorkrebs!

I normally don’t cover pre-prints in the blog, preferring to wait until the final, paginated version is out. But the pre-print for the Marmorkrebs genome by Gutekunst and colleagues is attracting international attention from journalists, and its Altmetric score is climbing fast. This post will collect news articles related to this paper.

I’ve been waiting the better part of a decade for this. After blogging about this in 2009, I’ve complained about the lack of a crayfish genome for years (2011, 2012, 2015, and 2016 at least). The portal for the genome is here.

This paper also provides the second major snapshot of the spread of Marmorkrebs in Madagascar. While previous papers showed it was in many places around the capital, this one shows just how far Marmorkrebs has spread.

5 February 2018

Invasion of the clones – Frank Lyko, Nature Ecology and Evolution “Behind the paper” blog post

A clonal crayfish from nature as a model for tumors – EurekAlert press release

An aquarium accident may have given this crayfish the DNA to take over the world – Elisabeth Pennisi, Science (duplicated, with different byline, here)

A pet crayfish can clone itself, and it’s spreading around the world - Sarah Zhang, The Atlantic (reprinted “‘We’re being invaded by an army of clones’; Plot twist: They’re crawfish” with “Advocate staff” byline in The Advocate)

This mutant crayfish clones itself, and it’s taking over Europe – Carl Zimmer, The New York Times (reprinted in the Toronto Star, Pittsbugh Post-Gazette, Deccan Herald)

Cloned crayfish conquers the world – Stephen Fleischfresser, Cosmos

Attack of the clones: Creature that started as pet now multiplying out of control
– Kristin Hugo, Newsweek

Marmorkrebs-Klone übernahmen Madagaskar in nur einem Jahrzehnt (Marble crayfish clones took over Madagascar in just a decade) – Jan Osterkamp, Spektrum der Wissenschaft

Marmorkrebse: Weltweite Ausbreitung durch Klone (Marble crayfish: Worldwide spread by clones) – Pharmazeitische Zeitung

Invasion der Krebsklone (Invasion of the crayfish clones)ORF.at

Crayfish evolved from pet to pest - Nature Asia blog

A species of crayfish has the ability to clone itself – Jonathan Kesh, Outer Places

Marmorkrebs: Eine Klon-Armee dient der KrebsforschungBR

6 February 2018

Mutant crayfish learned to clone itself in a German pet store and is now taking over Europe – Immanuel Jotham, International Business Times

Mutant crayfish invading the world originates from 1 single femaleRT

Significant Digits For Tuesday, Feb. 6, 2018 – Walt Hickey, Five Thirty Eight

Growing population of crayfish has one female ancestor Sarah Gibbens, National Geographic

Female mutant crayfish that can CLONE themselves are multiplying out of control and taking over parts of Europe and Africa – Cecile Borkhataria, The Daily Mail

Real life crayfish are born pregnant just like fictional Star Trek Tribbles – Brian Wang, Next Big Future

Geneticists unravel secrets of super-invasive crayfish – Ewan Callaway, Scientific American

The mutant, all-female crayfish that reproduce by cloning themselves – Natasha Frost, Atlas Obscura

Massive crayfish that didn’t exist 25 years ago are capable of cloning themselves — and it's terrifying scientists – Ashley Lutz, Business Insider (also Business Insider Nordic and Science Alert)

This little crayfish could take over the world – Noel Kirkpatrick, Earth Matters

Scientists say marbled crayfish have the DNA to take over the worldOutdoorHub

Mutant crayfish goes from zero to teeming in 25 years: video – Janet Pickel, PennLive

A mutant species of crayfish that reproduces asexually is taking over Europe – seriously! – Aaron Homer, The Inquisitr

Cloned pet crayfish self-spawning out of control – Clyde Hughes, Newsmax

These all-female, asexually reproducing mutant crayfish are the future liberals want – Julia Reinstein, BuzzFeed News (URL hints at original title: “Bring on the craytriarchy”)

Mutant, self-cloning crayfish are our new feminist #goals – Heather Schwedel, Slate

‘Cloverfield’ crayfish created a new species of self-replicating female mutants – Jamie Seidel, News.com.au (also at Fox News, New York Post, Springfield Daily Record, and NT News)

Mutant crayfish got rid of males, and its clones are taking over the world – John Timmer, Ars Technica (reprinted at SogoTech News)

‘They're coming!’: Mutant all-female crayfish are cloning themselves at an incredible rate - Wolfgang Stein interview, As It Happens

Marbled crayfish that can clone themselves originated from one mutant ancestor – Allan Adamson, Tech Times

A invasão dos clones: espécie mutante de lagostim se espalha pelo mundo – Sergio Matsuura, O Globo

Kreeft geeft wellicht meer zicht op kanker – Willen Schoonen, De Morgen

Georgia crawfish mutates into new species, takes over Europe – Christopher Buchanan, WXIA Atlanta

Mutant female crawfish invade Europe: report – Todd Price, NOLA.org

This self-cloning crawfish is invading Europe, report says – Jacqueline Quynh, Kevin Dupuy, WWL TV

7 February 2018

All-female crayfish species that didn’t exist 30 years ago reproduces by cloning itselfBT

Voracious mutant female crayfish clone themselves, taking over worldNewshub

Il gambero che si clona e va alla conquista del mondo (The shrimp that clones and goes to conquer the world) – Focus

自分自身のクローンを作り出して爆発的に増殖していくザリガニ (Crayfish that grow their own clones and grow explosively) – LiveDoor news

All-female mutant crayfish that clone themselves are taking over rivers and lakes around world - Josh Gabbatiss, The Independent

Mutant, all-female crayfish spreading rapidly through Europe can clone itself – Patrick Barkham, The Guardian (also at Gulf News Europe)

Shell shock: why crayfish replicants are taking overThe Guardian

All-female crayfish species that didn’t exist 30 years ago reproduces by cloning itselfAberdeen Evening Express

A mutant crayfish is cloning itself – Vadim Caraiman, Health Thoroughfare

Texas Standard: February 7, 2018 (mp3 file) - Zen Faulkes interview (starting at 25:44), Texas Standard, National Public Radio

Cloned Crayfish – Or Is It Crawfish – Could Be Coming To Texas Waters – Michael Marks, KUT (based on Texas Standard interview above)

Could the process that has apparently caused natural parthenogenesis in marbled crayfish be applied to cause parthenogenesis in humans? – Quora question

What do you think about the marble crayfish’s “cloning” ability? – Quora question

Marmorkrebs - Resistente Keime - Wasserstoffautos - Handyklau - WDR 5 Leonardo - Wissenschaft und mehr (mp3 file) – Science on Player FM (podcast)

Who needs a man? All-female mutant crayfish taking over the world, scientists say – Fira Pizani, Atlanta Journal-Constitution (also at Palm Beach Post and Austin American-Statesman)

New ‘mutant’ crayfish species is entirely female and don’t need no man – Mike Wehner, BGR

25 years ago, a mutant American crayfish turned to asexual reproduction, and all of Europe's lakes are filling up with its clonesBoing Boing

Who needs a man, anyway? These mutant crayfish sure don't – Kyle Fitzpatrick, Popsugar

The attack of the mutant crayfish – Bill Colley, KLIX

All-female crayfish in Europe can clone itself – Jose Vanhorne, Intelligencer

Marbled crayfish that can clone themselves originated from one mutant ancestorBrinkwire

Die „Tausend Töchter“ des Klon-Krebses und wie sie der Krebsforschung helfen (The "thousand daughters" of clone crayfish and how they help cancer research) – Sibylle Kohlstädt, Labor Praxis

8 February 2018

Crayfish clones – Kerri Smith and Adam Levy, Nature Podcast segment

If a crayfish didn't exist 25 years ago, how did it come into being? – Quora question

Marbled crayfish population explosion result of self cloning - Joanna Lentini, Dive Photo Guide

Crayfish shocked scientists by cloning itselfNetral English

A “parthenogenetic” crayfish reproduces without sex: is it a new species? – Jerry Coyne, Why Evolution is True blog

Marbled Crayfish Population Explosion Result of Self CloningViral News

Invasive new species of crayfish are cloning themselves – Chrissy Sexton, Earth.com

Cloning In nature: All marbled crayfish clones of one individual femaleCetus News

Scientists track spread of invasive crawfishUndercurrent News

Food for dirty thoughts: Sexual-fetish expert tantalizes with tales from her trade on BPR – Moses Jefferson, Brooklyn Paper Record podcast (seriously, there is discussion of marbled crayfish in there)

Crayfish that clones itself could be used as model for cancer research – Lauren Scrudato, Laboratory Equipment

Mutant clones of Georgia crawfish besiege planet – George Mathis, Atlanta Journal Constitution “News to Me” blog

Self-cloning mutant crayfish are taking over Europe, but really no big deal – Jeff Vrabel, Golf Digest

Mutant crayfish can clone itself and they are all females – Salve Juris, Kicker Daily News

9 February 2018

This crayfish has mutated into a super-gross tribble nightmare – Beth Elderkin, io9

The asexual clonal crayfish that could teach us about tumor development &ndash Alayna Hansen, New Atlas

Crayfish clone invasionGenome Web

ICYMI: Sex lives of crayfish, CO2 Is “the gas of life,” & more – Paul Rauber, Sierra Club

I’m just a misunderstood marbled crayfish (overlord) who is certainly not planning world domination – Josh Sippie, McSweeney’s

All-female crayfish in Europe can clone itselfDuta

10-12 February 2018

Female mutant crayfish clones have landed, but government recommends you not buy one – Catherine Tunney, CBC

Feminine mutant crayfish clones have landed, however authorities recommends you not purchase one – Staff, Luxora Leader

Weird species of crayfish has mutated to the point they can clone themselves – Stewart Perrie, LAD Bible

Thumbs up, thumbs downHouston Chronicle blog

is it a shrimp? is it a prawn? no - it's super crayfish! – Alison Campbell, Bio Blog

Incredible species of crayfish are able to clone themselvesDollar Viral

Q&A: Will mutant crayfish impact future of crawfish? – Leigh Frillici, KPRC

11 of our best weekend reads – Kaly Soto, The New York Times

Evolution caught in the act: a Darwin Day sampler pack – Stephanie Savage, Miracle Girl blog

Crayfish can clone themselves and might take over the world – Jessica Goddard, BrainJet

This new species can clone itself by the thousands — and could help scientists understand cancer – Travis Gettys, Raw Story

Attack of the (crustacean) clones – Abby Bigler, The Quad

Self-cloning marbled crayfish spreading across the worldThe Week

New crayfish that doesn't need males to mate becomes all-powerfulBBC

Mutant all-female crayfish prompt invasive species fearsDeutsche Welle

The crayfish ditches reproduction, turns to cloning (study) – Jose Buttner, Regal Tribune

Mutant female crayfish can breed alone and multiply at alarming rate – Sean Morrison, Evening Standard

Mutant crayfish alarms experts around the world – Dan Taylor, Morning Ticker (also at
Build a Better World News)

12 February 2018

Self-cloning marbled crayfish spreading across the world – Rebecca Gillie, MSN News

Attack of the clones: animal parthenogenesis – mountainwashere, Steemit

Crayfish Spiders Bees Grouse and Ungulates – Hurst and Carol, Creature Feature blog

14 February 2018

Klonende kreeft kan kankeronderzoekers inspireren (Cloning crayfish can inspire cancer researchers) – Gemma Venhuizen, NRC Handelsblad

These asexual animals don’t need love on Valentine’s Day (or any day) – Ryan F. Mandelbaum, Gizmodo

Self-reproducing crayfish species threatens ecosystems around the world – Jerry Xia, IR Insider

15 February 2018

Lang’s World: Ten Pearls of Whitaker’s wit and wisdom on sports and beyond 2.15.18 – Lang Whitaker, Grind City Media / Memphis Grizzlies

16 February 2018

Is the new species, Marmorkrebs, resulting from a crayfish genetic mutation an invasive new species or an evolutionary change? What are the benefits asexual cloning similar to tribbles on the legendary Star Trek episode?Quora question

19 February 2018

The crisis with crayfish – Lobsters that breed like Star Trek’s tribbles are conquering Europe – Michael Rosch, Adventures in Poor Taste

22 February 2018

News of the Weird: Feb. 22, 2018 – Editors at Andrews McNeel Syndication, Shepard Express

News of the Weird: A Valentine's Divorce – Editors at Andrews McNeel Syndication, Creative Loafing

1 March 2018

God’s natural cloning – Anonymous, Does God Exist? Today blog

3 March 2018

SoT 287: An Army of Clones – Ed Brown, Dr. Shayne Joseph, Penny Dumsday, Lucas Randall, Science on Top (podcast); starts 12:34

6 March 2018

Creationists and crayfish – Raymond Ramirez, The Observer (student newspaper)

Mutant strain of crayfish damages wetlands – Harold Allison, Washington Times Herald

9 March 2018

The wider debate about workplaces gives facilities managers a chance to crack the code
– Mark Eltringham, Insight

Tribbles and crayfish – William V. Raszka, AAP Journals blog

21 March 2018

Meet the mutant, self-cloning crayfish that has scientists scratching their heads — Benjamin Pineros, Techly

Mutant fish that CLONES itself and is taking over rivers worldwide leaves experts baffled – Rachel O'Donoghue, Daily Star

22 March 2018

More and more marbled crayfish – Anonymous, World Book Behind the Headlines (blog)

25 March 2018

Untitled ("Crayfish apocalypse") – Wiley, Non Sequiter (comic)

30 March 2018

The end of male usefulness – Mike Cox, The Columbia Star

1 April 2018

Mutant crayfish that clones itself may help unlock cancer secrets – Anonymous, Aseanews

1 May 2018

Pinpointing the origin of marbled crayfish clones ndash; Diana Kwon, The Scientist

Related posts

Olivia’s fantasy genomes

External links

The genome portal for the marbled crayfish

16 January 2018

Kubiak and Pellett, 2018

Kubiak M, Pellett S. 2018. Invasive alien species legislation: a veterinary perspective. Companion Animal 23(1): 44-48. https://doi.org/10.12968/coan.2018.23.1.44


The European Union (EU) Invasive Alien Species (IAS) Regulation (1143/2014) restricts keeping of named species, in order to preserve native biodiversity. As some of these species are currently kept by private exotic animal keepers, zoological collections and animal encounter businesses, it is important for veterinary surgeons to be aware of the restrictions. As of August 2017, new species have been added to the legislation; this article reviews the previous situation and includes the updated information.

Keywords: invasive alien species • legislation • Tamias sibiricusProcyon lotorTrachemys scriptaNasua nasua

Maguire and colleagues, 2018

Maguire I, Klobučar G, Žganec K, Jelić M, Lucić A, Hudina S. 2018. Recent changes in distribution pattern of freshwater crayfish in Croatia − threats and perspectives. Knowledge and Management of Aquatic Ecosystems 419: 2. https://doi.org/10.1051/kmae/2017053


Analysis of Croatian freshwater crayfish populations, aiming to gather new distributional data and complement previous surveys (2005–2011), was performed during 2014–2016, within the frame of Natura 2000 Integration Project. The research included different waterbodies across the whole of Croatia, harbouring both indigenous and non-indigenous crayfish species (ICS and NICS, respectively). Field work was conducted in 117 grid squares with dimensions 10 × 10 km, and up to four waterbodies were surveyed per grid square, making a total of 450 studied sites. Out of those, crayfish were not recorded in 368 sites. In the sites with crayfish presence (i.e., 82), the most frequently observed ICS was Astacus astacus (registered in 33 sites) followed by Austropotamobius pallipes (16 sites), Austropotamobius torrentium (12 sites), and Astacus leptodactylus (5 sites). Concerning NICS, the majority of records were for Orconectes limosus (13 sites), followed by Pacifastacus leniusculus (2 sites), whereas Procambarus fallax f. virginalis was registered in only one locality. Comparisons of obtained data with those from previous surveys showed that NICS are progressively spreading and displacing ICS, as recorded for A. leptodactylus that was almost completely displaced by O. limosus in waterbodies of the east Croatia. Existing ICS populations are under growing anthropogenic preassure, frequently fragmented and isolated. Moreover, this survey showed that in the last decade 55% of A. astacus and 67% of A. pallipes populations disappeared mainly as a consequence of anthropogenic influence onto their habitats. Further monitoring and conservation actions for ICS should be urgently applied to mitigate negative impacts of both NICS and anthropogenic influence.

Keywords: noble crayfish • narrow-clawed crayfish • stone crayfish • white-clawed crayfish • non-indigenous crayfish species