22 June 2017

Lyko, 2017

Lyko F. 2017. Ein Krebs für die Krebsforschung. Biologie in unserer Zeit 47(3): 172–177. http://dx.doi.org/10.1002/biuz.201710620


Marmorkrebs (or marbled crayfish) is a triploid crayfish known since the mid-1990s, which reproduces parthenogenetically. It originated from the North American decapod species Procambarus fallax and was distributed as a popular aquarium pet. Subsequent anthropogenic releases have resulted in the establishment of several stable populations in the wild that constitute a serious invasive threat. Interestingly, marbled crayfish use a parthenogenetic mode of reproduction that results in the generation of clones with minimal genetic variation. In addition, the animals can be easily bred and manipulated in the laboratory. These features establish marbled crayfish as a novel and innovative model organism for tumor biology, particularly for the analysis of clonal evolution and epigenetic adaptation of tumor genomes.

Keywords: Marmorkrebs • tumor biology • clonal evolution • epigentics

(Note: The main text of the article is in German. Keywords are translated from German.)

12 June 2017

Martin and colleagues, 2016

Martin A, Serano JM, Jarvis E, Bruce HS, Wang J, Ray S, Barker CA, O’Connell LC, Patel NH. 2016. CRISPR/Cas9 mutagenesis reveals versatile roles of Hox genes in crustacean limb specification and evolution. Current Biology 26(1): 14-26. https://doi.org/10.1016/j.cub.2015.11.021


Crustaceans possess a diverse array of specialized limbs. Although shifts in Hox gene expression domains have been postulated to play a role in generating this limb diversity, little functional data have been provided to understand the precise roles of Hox genes during crustacean development. We used a combination of CRISPR/Cas9-targeted mutagenesis and RNAi knockdown to decipher the function of the six Hox genes expressed in the developing mouth and trunk of the amphipod Parhyale hawaiensis. These experimentally manipulated animals display specific and striking homeotic transformations. We found that abdominal-A (abd-A) and Abdominal-B (Abd-B) are required for proper posterior patterning, with knockout of Abd-B resulting in an animal with thoracic type legs along what would have been an abdomen, and abd-A disruption generating a simplified body plan characterized by a loss of specialization in both abdominal and thoracic appendages. In the thorax, Ubx is necessary for gill development and for repression of gnathal fate, and Antp dictates claw morphology. In the mouth, Scr and Antp confer the part-gnathal, part-thoracic hybrid identity of the maxilliped, and Scr and Dfd prevent antennal identity in posterior head segments. Our results allow us to define the role Hox genes play in specifying each appendage type in Parhyale, including the modular nature by which some appendages are patterned by Hox gene inputs. In addition, we define how changes in Hox gene expression have generated morphological differences between crustacean species. Finally, we also highlight the utility of CRISPR/Cas9-based somatic mutagenesis in emerging model organisms.

Keywords: None provided.

Note: Marmorkrebs appear in Figure 7D, described in the main text with the incomplete species name, “Procambarus fallax.” The Supplemental Experimental Procedures provide the full name, confirming that these are Marmorkrebs.

23 May 2017

Veselý and colleagues, 2017

Veselý L, Hrbek V, Kozák P, Buřič M, Sousa R, Kouba A. 2017. Salinity tolerance of marbled crayfish Procambarus fallax f. virginalis. Knowledge and Management of Aquatic Ecosystems 418: 21. https://doi.org/10.1051/kmae/2017014


Eastern Europe comprises a significant part of the native ranges for indigenous crayfish species (ICS) belonging to the genus Astacus. This region has been largely overlooked by astacologists and considered relatively immune to the impacts of non-indigenous crayfish species (NICS). The recent discovery of two marbled crayfish Procambarus fallax f. virginalis populations in Ukraine has changed this view. Increased propagule pressure (mainly due to pet trade) has raised concerns of NICS which may negatively impair the ecosystems of Azov, Black and Caspian Seas and their tributaries inhabited by ICS. In this study, we provide the first insight into salinity tolerance of marbled crayfish. We performed a 155-day experiment using 5 different salinities (6, 9, 12, 15, and 18 ppt) and a freshwater control. Evaluation of survival, growth and reproduction suggests that marbled crayfish have a lower salinity tolerance than other crayfish species, which may limit their invasive potential in brackish environments. However, its ability to survive for more than 80 days at 18 ppt opens up the possibility of gradual dispersion and adaptation to brackish conditions. Our study highlights the need for further studies elucidating the potential for marbled crayfish to negatively impair these ecosystems.

Keywords: brackish environment • growth • reproduction • moult • survival

26 April 2017

Could Marmorkrebs be the youngest species?

Q: Which species is the youngest on Earth?

A: Impossible to know for sure, but here is a candidate: the marbled crayfish, also known as Marmorkrebs.

It was discovered in aquariums in the mid 1990s, and has no known natural populations. It’s so unusual that if it was out there, it should have been noticed.

A major genetic difference between Marmorkrebs and their nearest relative is that Marmorkrebs is triploid: it has three sets of chromosomes, not two. The switch from two to three sets of chromosomes can occur in a single step, in one generation.

These give us some reason to believe it literally might not have existed long before the 1990s.

External links

Which species is the youngest on Earth?

14 April 2017

More Marmorkrebs in Japan

War is in the air. Even against marbled crayfish, with a headline from Japan urging “war” against the species.

A news article is reporting the second finding of Marmorkrebs in Japan, and, worryingly, it reports multiple individuals spread across two years, suggesting a population has been established. And it is on a completely different (and more southern) island than previously. Based on modelling work I helped co-author a few years ago (Faulkes et al. 2012), that region is high quality habitat for Marmorkrebs (see Figure 5 in particular).

The map of Marmorkrebs introductions has been updated, although I suspect the crayfish were not found anywhere near so close to the mouth of the river.


Faulkes Z, Feria TP, Muñoz J. 2012. Do Marmorkrebs, Procambarus fallax f. virginalis, threaten freshwater Japanese ecosystems? Aquatic Biosystems 8: 13. http://dx.doi.org/10.1186/2046-9063-8-13

External links

War urged to destroy alien cloning mystery crayfish

29 March 2017

Vogt, 2017

Vogt G. 2017. Facilitation of environmental adaptation and evolution by epigenetic phenotype variation: insights from clonal, invasive, polyploid, and domesticated animals. Environmental Epigenetics 3(1): dvx002. http://dx.doi.org/10.1093/eep/dvx002


There is increasing evidence, particularly from plants, that epigenetic mechanisms can contribute to environmental adaptation and evolution. The present article provides an overview on this topic for animals and highlights the special suitability of clonal, invasive, hybrid, polyploid, and domesticated species for environmental and evolutionary epigenetics. Laboratory and field studies with asexually reproducing animals have shown that epigenetically diverse phenotypes can be produced from the same genome either by developmental stochasticity or environmental induction. The analysis of invasions revealed that epigenetic phenotype variation may help to overcome genetic barriers typically associated with invasions such as bottlenecks and inbreeding. Research with hybrids and polyploids established that epigenetic mechanisms are involved in consolidation of speciation by contributing to reproductive isolation and restructuring of the genome in the neo-species. Epigenetic mechanisms may even have the potential to trigger speciation but evidence is still meager. The comparison of domesticated animals and their wild ancestors demonstrated heritability and selectability of phenotype modulating DNA methylation patterns. Hypotheses, model predictions, and empirical results are presented to explain how epigenetic phenotype variation could facilitate adaptation and speciation. Clonal laboratory lineages, monoclonal invaders, and adaptive radiations of different evolutionary age seem particularly suitable to empirically test the proposed ideas. A respective research agenda is presented.

Keywords: epigenetic variation • adaptation • general-purpose genotype • speciation • genome reconfiguration • monoclonal invaders

28 March 2017

More like “guidelines”

Smithsonian Magazine has an article on interesting variations in reproduction featuring eight different species. Marmorkrebs clock in at number three!

Also included are sharks, mollies, lizards, and salamanders. Mammals got nothin’ when it comes to their reproductive practices.

External links

Meet Eight Species That Are Bending the Rules of Reproduction

27 February 2017

Velisek and colleagues, 2017

Velisek J, Stara A, Zuskova E, Kouba A. 2017. Effects of three triazine metabolites and their mixture at environmentally relevant concentrations on early life stages of marbled crayfish (Procambarus fallax f. virginalis). Chemosphere 175: 440-445. http://dx.doi.org/10.1016/j.chemosphere.2017.02.080


The sensitivity of early life stages of marbled crayfish (Procambarus fallax f. virginalis) to chronic exposure of one out of three triazine metabolites (terbuthylazine 2-hydroxy – T2H, terbuthylazine-desethyl – TD, and atrazine 2-hydroxy – A2H) and their mixture at maximal environmentally real concentrations was evaluated under laboratory conditions. The effects were assessed on the basis of mortality, growth, development, oxidative stress biomarkers, antioxidant enzymes activity and histopathology. Single metabolites (T2H – 0.73 μg/L; TD – 1.80 μg/L; A2H – 0.66 μg/L) and their mixture were not associated with negative effects on mortality, behaviour and early ontogeny, however, two metabolites (TD and A2H) and mixtures caused significantly lower growth and significantly higher catalase activity of early life stages of marbled crayfish. No histopathological changes of gills were observed after exposure to all tested triazine treatments, however, apparent histological differences in structural cells organization such as superiority in numbers of lipid resorptive cells were recorded in after exposition to TD and mixture. In conclusion, this study shows potential risk of using triazine herbicides in agriculture due to effects of their degradation products on non-target organisms.

Keywords: antioxidant enzyme • developmental stage • histopathology • oxidative stress • toxicity test

13 February 2017

Koutnik and colleagues, 2017

Koutnik D, Stara A, Zuskova E, Kouba A, Velisek J. 2017. The chronic effects of terbuthylazine-2-hydroxy on early life stages of marbled crayfish (Procambarus fallax f. virginalis). Pesticide Biochemistry and Physiology 136: 29-33. http://dx.doi.org/10.1016/j.pestbp.2016.08.008


This study assessed the chronic effects of terbuthylazine-2-hydroxy (T2H), one of the main terbuthylazine degradation products, on early life stages of marbled crayfish (Procambarus fallax f. virginalis) by means of mortality, growth rate, early ontogeny, oxidative stress, antioxidant defence and histopathology. The crayfish were exposed to four concentrations of the tested substance as follows: 0.75 μg/l (environmental concentration), 75, 375 and 750 μg/l for 62 days. Concentrations over 75 μg/l caused lower weight compared to the control group. T2H at 750 μg/l caused delay in ontogenetic development. Levels of thiobarbituric acid reactive substances and total superoxide dismutase activity were significantly (p < 0.01) lower in groups exposed to 375 and 750 μg/l T2H. Crayfish in these treatments also showed alteration of tubular system including disintegration of tubular epithelium with complete loss of structure in some places of hepatopancreas and wall thinning up to disintegration of branchial filaments with focal infiltrations of hemocytes. In conclusion, chronic terbuthylazine-2-hydroxy exposure in concentrations up 75 μg/l (100 times higher than environmental concentration) affected growth, ontogenetic development, antioxidant system, caused oxidative stress and pathological changes in hepatopancreas of early life stages of marbled crayfish.

Keywords: triazine • early development • histopathology • oxidative stress •antioxidant enzymes

08 February 2017

Eighteenth Crustaceologentagung

The 18th meeting of German speaking carcinologists (Crustaceologentagung) will be held from 30 March to 2 April 2017 at the Humboldt-Universität zu Berlin. Visit the website (and maybe Google Translate) for more information.

Although now that I think about it, if you need Google Translate to understand the web page, you probably wouldn’t get much out of the meeting.

External links

07 February 2017

How could I miss Croatia?

I’m red-faced. It’s about two years since a short note appeared mentioning the discovery of Marmorkrebs in northern Croatia (Samardžić et al. 2014). This is one I should have caught, too, since it appeared in the newsletter of the International Association of Astacology, of which I am a member! Always read the newsletters of your professional societies, citizens!

I have updated the map of Marmorkrebs introductions with this record, and others (more recent – hadn’t missed them,. just hadn’t added them) in the Czech republic.


Patoka J, Buric M, Kolár V, Bláha M, Petrtýl M, Franta P, Tropek R, Kalous L, Petrusek A, Kouba A. 2016. Predictions of marbled crayfish establishment in conurbations fulfilled: evidences from the Czech Republic. Biologia 71(12): 1380–1385. https://doi.org/10.1515/biolog-2016-0164

Samardžić M, Lucić A, Maguire I, Hudina S. 2014. The first record of the marbled crayfish (Procambarus fallax (Hagen, 1870) f. virginalis) in Croatia. Crayfish News 36(4): 4. http://www.freshwatercrayfish.org/docs/cn/CrayfishNews_36(4)_hr.pdf

06 February 2017

Call for crustacean papers: Fishes

Even though I have been a working professional scientist for some time, there are always more journals than time, so I am always on the lookout for journals that would be appropriate for Marmorkrebs papers.

When I first saw the journal Fishes, I though, “This is not for me, because I don’t study animals with backbones.” But despite the title, Fishes takes papers on invertebrates, too. The journal’s mandate includes “aquatic life science and aquatic animals (fishes, molluscs and crustaceans, both fresh water and marine).”

Fishes caught my eye for a few reasons.

It is a new journal, it is open access, and they are waiving article processing charges for articles published in 2017. Given that the main reason I see people not publishing open access is that people are unable to pay article processing fees, offering free publication as an “introductory offer,” as it were, is interesting to many researcher.

That said, while this journal doesn’t have much of a track record yet, the publisher, MDPI, has a mixed track record at best.

In brief, on the negative column, MDPI journals have published several very poor papers. They have also sent out a lot of unsolicited emails (this post was prompted by one).

On the positives column, MDPI is a member of the Directory of Open Access Journals and the Committe on Publication Ethics. The Fishes editor-in-chief appears to be a real person. Richard Poynder has a thorough article and interview from 2015 covering the debates about whether the Fishes publisher could be rightfully called a “predatory publisher.” Scammers are typically not as transparent as MDPI owner Shu-Kun Lin is in this interview, although some of his answers give me pause.

And publishing articles for free – as Fishes is doing this year – would be an incredibly bad scam.

External links

The Open Access Interviews: Publisher MDPI
Is MDPI a reputable Academic Publisher?

23 January 2017

New International Association for Astacology website

 The new site for the professional society for all things crayfish is now:


The relaunch is looking pretty sharp, I must say! The landing page has a lovely rotating gallery of very high resolution crayfish pictures.

19 January 2017

Falckenhayn, 2016

Falckenhayn C. 2016. The methylome of the marbled crayfish Procambarus virginalis. Doctoral dissertation, Combined Faculties for the Natural Sciences and for Mathematics, University of Heidelberg, Heidelberg. http://archiv.ub.uni-heidelberg.de/volltextserver/22489/1/Falckenhayn_Cassandra_PhDThesis.pdf


DNA methylation in invertebrates seems to play a different role as in mammals and its evolutionary conservation among invertebrates is unclear. Only two studies describe crustacean methylomes giving just a small overview. The parthenogenetic reproducing marbled crayfish display a high environmental adaptability besides its genetic uniformity and thus, possess the necessary attributes of a laboratory model organism. The aim of this work was to characterize the methylome of the marbled crayfish at single-base resolution using whole-genome bisulfite sequencing in an attempt to give new insights into DNA methylation in crustaceans and thus, in the evolutionary conservation among invertebrates. Analysis of the mitochondrial DNA of different marbled crayfish strains revealed a single origin and suggests to consider the marbled crayfish as independent asexual species Procambarus virginalis. Furthermore, since the P. virginalis possess a large genome size, the transcriptome was assembled and comparison to other species revealed a relative good quality of the first draft transcriptome as well as the presence of a conserved DNA methylation system in P. virginalis. Analysis of the CpG depletion in protein-coding sequences and mass spectrometry confirmed historical germline and current DNA methylation in various tissues of P. virginalis. The methylome was characterized by the key features of animal methylomes with methylation targeted to gene bodies. The gene bodies displayed the typical pattern of a mosaically methylated invertebrate genome and a bimodal distribution of their methylation levels. Targeted gene bodies were annotated as housekeeping genes and methylation showed a parabolic relationship to housekeeping gene expression suggesting that the DNA methylation of housekeeping genes might fine-tune their expression. Additionally, repeats were generally hypomethylated and the methylation of repeats depended on their position to gene bodies. Finally, inter-individual and inter-tissue comparison of gene body methylation revealed a high reproducibility of the methylation patterns, while inter-species comparison between P. fallax and P. virginalis displayed an overall hypomethylation in the P. virginalis genes which however, could not explain the by mass spectrometry detected global hypomethylation in P. virginalis. These findings uncovered that the P. virginalis methylome is characterized by tissue-invariant housekeeping gene methylation. This thesis describes novel insights into the evolutionary conservation of gene body and repeat methylation in invertebrates, especially crustaceans, and the preferential methylation of housekeeping genes highlights a functional difference to the tissue-specific methylation in mammals.

Keywords: None provided.

Patoka and colleagues, 2016

Patoka J, Buřič M, Kolář V, Bláha M, Petrtýl M, Franta P, Tropek R, Kalous L, Petrusek A, Kouba A. 2016. Predictions of marbled crayfish establishment in conurbations fulfilled: Evidences from the Czech Republic. Biologia 71(12): 1380–1385. https://doi.org/10.1515/biolog-2016-0164


The marbled crayfish (Procambarus fallax f. virginalis) has become one of the potentially most dangerous nonindigenous crayfish species spreading in European countries and elsewhere. This taxon reproduces parthenogenetically and recently has been verified as a vector of the crayfish plague pathogen. Here, we report on two established populations of marbled crayfish in the Czech Republic. The marbled crayfish was observed during autumn 2015 in an urban pond connected by sewer piping with the Rokytka brook near its mouth to the Vltava River in Prague. Subsequently, three adult females, two of them having well-developed glair glands and oocytes, were captured in this pond during spring 2016, suggesting successful overwintering of the local population. Furthermore, four adult females were captured in an artificial pond at the Radovesická lignite spoil heap in the vicinity to the industrial conurbation of Bílina in summer 2016; one of them carried eggs. We tested these for the presence of the crayfish plague pathogen Aphanomyces astaci, with negative results. The introduction pathway for both populations is most likely a release from private aquaria, as these sites are popular for recreation activities. Our findings substantiate previous predictions that conurbations are likely to be the primary areas for marbled crayfish introductions.

Keywords: Procambarus fallax f. virginalis • biological invasion • first record • pet trade • Marmorkrebs • urban pond • postmining site

10 January 2017

Awards and scholarships for crustacean research, 2017

The Crustacean Society (TCS) has multiple scholarships and travel grants for its members.

Scholarships in graduate studies

The Crustacean Society annually awards up to six US$1000 scholarships in graduate studies on crustaceans in any of the following fields:

  • Biology of large branchiopods (Denton Belk Memorial Scholarship)
  • Physiology and reproductive biology
  • Ecology and behavioural ecology, population genetics, and behavior
  • Eystematics, biogeography, and evolution
  • Larvae and development
  • Anatomy or paleobiology

Applicants and their faculty sponsor must be a member of The Crustacean Society and be enrolled in an undergraduate or graduate degree program.

Student travel awards

The Crustacean Society awards up to ten US$450 awards to support student attendance at Crustacean Society meetings (Society for Integrative and Comparative Biology, mid-year society meeting, or the International Crustacean Congress). Applicants and their faculty sponsor must be a member of The Crustacean Society, be enrolled in an undergraduate or graduate degree program, be the presenter of an oral or poster presentation at the Crustacean Society meeting they attend and demonstrate financial need for society support of travel to the meeting.

Early-career, post-Ph.D. travel awards

The Crustacean Society will award up to three US$1500 travel grants for early-career researchers with a Ph.D. awarded within 5 years of the application deadline. Extension of up to 8 years post-Ph.D. will be considered at the discretion of the Program Officer for applicants having taken a career break for family reasons. The grants shall cover travel to present results of their research in any field of study involving crustaceans at a Crustacean Society meeting (Society for Integrative and Comparative Biology, mid-year society meeting, or the International Crustacean Congress). The applicant must be a current member of The Crustacean Society at the time of application.

The closing date for all awards is 31 March 2017. Contact Dr. Joanne Taylor (jtaylor@museum.vic.gov.au) for more information. She is traveling until about Jan. 20, 2017; in the meantime, contact Mary Belk for forms (tcs1921@hotmail.com).

09 January 2017

Chucholl and Wendler, 2017

Chucholl C, Wendler F. 2017. Positive selection of beautiful invaders: long-term persistence and bio-invasion risk of freshwater crayfish in the pet trade. Biological Invasions 19(1): 197-208. http://dx.doi.org/10.1007/s10530-016-1272-5


After interest in keeping crayfish (Crustacea, Decapoda, Astacida) in home aquaria peaked in the mid-2000s, the aquarium trade has become a novel introduction pathway for non-native crayfish species in Germany. Here, we provide an update on the ornamental crayfish trade approximately one decade after the ‘crayfish hype’ to explore the long-term implications in terms of bio-invasion risk. Specifically, species’ availability in e-commerce and potential invasiveness were assessed and compared to previous studies. Morphological and ecological traits of the offered species were compiled and related to their long-term availability (covering 2005–2015). In July 2015, a total of 31 online shops offered 28 crayfish species, which represents a decline of 24% in species diversity compared to the late 2000s. The estimated rate of import of new species has considerably flattened and approaches pre-hype values (<1 species year−1). However, the risk associated with the offered species, as assessed by a risk screening tool, has not decreased compared to the late 2000s. Long-term availability in the trade was primarily determined by bright coloration, the ability to reproduce under warm aquarium conditions, and a preference for lentic habitats. Species featuring such traits are likely to persist in the aquarium trade and include four high-risk species, most notably invasive and crayfish plague-carrying red swamp crayfish (Procambarus clarkii) and Marmorkrebs (Procambarus fallax f. virginalis). Persistent propagule pressure from aquaria has substantially contributed to the establishment of both species in Germany, stressing the need for more effective pathway management.

Keywords: aquarium trade • Crustacea • risk assessment • pre-introduction selection