24 June 2019

Announcement: 23rd International Association of Astacology symposium

The 23rd International Association of Astacology symposium will be hosted the University of South Bohemia in the Czech Republic from June 29 to July 3, 2020.

The symposium will be held in Hotel Štekl, near the beautiful Hluboká nad Vltavou Château (pictured).

Planned topics including species diversity and distribution, conservation, physiology, genetics, ecology, ethology, diseases, fishery and aquaculture.

In addition to the scientific program, events will include trips to the experimental facilities of the University of South Bohemia, natural crayfish locality in the Šumava National Park, the Hluboká nad Vltavou Château, beer tasting with the Budweiser Budvar Brewery, the Český Krumlov UNESCO Heritage castle, and wooden rafting.

Abstract submission runs from 1 December 2019 to 15 April 2020.

Early registration deadline: 31 March 2020
Regular registration: 30 April 2020Late registration: 31 May 2020

External links

23rd Symposium of the International Association of Astacology

17 June 2019

Hossain and colleagues, 2019b

Hossain MS, Kubec J, Grabicová K, Grabic R, Randák T, Guo W, Kouba A, Buřič M. 2019. Environmentally relevant concentrations of methamphetamine and sertraline modify the behavior and life history traits of an aquatic invertebrate. Aquatic Toxicology 213: 105222. https://doi.org/https://doi.org/10.1016/j.aquatox.2019.105222


Pharmaceutically active compounds are major contaminants of aquatic environments that show direct and indirect effects on aquatic organisms even at low concentrations. The aim of this study was to assess the effects of the illicit drug methamphetamine and the antidepressant sertraline on clonal marbled crayfish Procambarus virginalis. Crayfish exposed to the environmentally relevant concentrations of methamphetamine of ∼1 μg L−1 did not exhibit significant differences from unexposed controls in distance moved, velocity, and activity level with or without available shelter. Sertraline-exposed (∼1 μg L−1) crayfish were significantly more active, regardless of available shelter, and moved greater distances when shelter was available, compared to control crayfish. Crayfish exposed to methamphetamine and sertraline spent significantly more time outside the shelters compared to controls. Sertraline-exposed crayfish spawned more frequently and showed higher mortality than controls. The results suggest that the low environmental concentrations of the tested compounds could alter the behavior and life history traits of crayfish, resulting in higher reproductive effort and mortality.

Keywords: aquatic pollutants • behavior • crayfish • life history traits • pharmaceuticals • Procambarus virginalis

07 June 2019

Updates from Denmark

It’s rare for crayfish news to get a follow-up, but the first record of Marmorkrebs in Denmark has attracted more attention by doing what Marmorkrebs do: reproducing.

Danish Marmorkrebs in berry

With the help of a Google Translate and guesswork (“crayfish” seems to translate into a lot of weird English words), I think the article says (in part):

It was bad news for the Danish nature when a marbled crayfish was found in Karup Å near Skive in February. It was the first time that the marbled crayfish was found in Denmark.

In other countries, the crayfish has done a lot of damage to nature, as it can fertilize itself and eat almost everything on its way. So since then, it has been kept in captivity at Aqua Aquarium in Silkeborg. Now it has succeeded in cloning itself and thus getting six kids.

If it first gets hold of the watercourses in Denmark, it is completely hopeless to stop it again, says Morten Vissing, is a zoologist at Aqua Aquarium and Animal Park.

“You have seen many strange things, but this is one of the things that hit everything. After all, it is not an animal that exists naturally. You have taken some animals from nature, and you have bred in colors and sizes. Then one has reached a species where today only females exist, and they are then able to clone themselves. It’s incredibly mysterious,” says Morten Vissing.

The marbled crayfish is the only species of crab known to reproduce asexually.

Vissing seems to imply that Marmorkrebs were bred deliberately, which is probably not the case. And either Vissing or the newspaper should read about spinycheek crayfish, which can reproduce asexually.

Related posts

Nothing like a Dane: the European invasion continues

External links

Den uønskede marmorkrebs har klonet sig selv (The unwanted marbled crayfish has cloned itself)

Celebrate diversity: Another member of Club Asexual

Asian water dragon (Physignathus cocincinus)

The list of parthenogenetic species slowly inches up. This time, it’s the Asian water dragon (Physignathus cocincinus) that continues increasing the list.

According to an interview on NPR, this discovery was made almost by happenstance. The policy of the zoo where the animals was kept was to toss unfertilized eggs. But someone thought, “Let’s try incubating them. It doesn’t take any time.”

Thus are discoveries made. Most eggs went bad, but the Asian water dragon’s... did not.

This makes me wonder just how many more species are capable of both sexual and asexual reproduction, and if there is a way to systematically test for this instead of just hoping for lucky accidents. 


KL Miller, Castañeda Rico S, Muletz-Wolz CR, Campana MG, McInerney N, Augustine L, Frere C, Peters AM, Fleischer RC. 2019. Parthenogenesis in a captive Asian water dragon (Physignathus cocincinus) identified with novel microsatellites. PLOS ONE 14(6): e0217489. http://doi.org/10.1371/journal.pone.0217489

External links

05 June 2019

Lipták and colleagues, 2019

Lipták B, Veselý L, Ercoli F, Bláha M, Buric M, Ruokonen TJ, Kouba A. Trophic role of marbled crayfish in a lentic freshwater ecosystem. Aquatic Invasions 14(2): 299-309. https://doi.org/10.3391/ai.2019.14.2.09


Species’ introductions may cause severe adverse effects on freshwater ecosystems and their biota. The marbled crayfish, Procambarus virginalis Lyko, 2017, is an invasive parthenogenetically reproducing crayfish with rapid reproduction, maturation and tolerance to a wide range of environmental conditions, which was introduced to many sites across Europe during the last decade. Due to its recent speciation and limited number of field studies, the knowledge of trophic interactions of the marbled crayfish in freshwater food webs is scarce. An invaded area located in Central Europe was studied to identify the marbled crayfish food web interactions using analysis of carbon 13C and nitrogen 15N isotopes. This study brings the first insight into the trophic ecology of marbled crayfish in lentic freshwater ecosystems. Algae and detritus were identified as the most important food sources for the marbled crayfish, while zoobenthos and macrophytes were less important. Moreover, the marbled crayfish was found to be an important food source for top fish predators, but marginal for omnivorous fish. Being able to utilize energy from the bottom of the trophic food web, the marbled crayfish may have important roles in the ecosystem, transferring energy to higher trophic levels. It processes allochthonous and autochthonous matter in the ecosystem, thus being a competitor to other organisms with similar food preferences and impacting zoobenthos, algae and macrophytes through predation or direct consumption. To sum up, the marbled crayfish has a strong ability to utilize food sources from different trophic levels, and, thanks to its life history, can be a highly adaptable invader.

Keywords: biological invasion • Central Europe • parthenogenetic species •
Procambarus virginalis • stable isotope

27 May 2019

Concealed crayfish and The Hidden Half

Marmorkrebs rarely make appearances in pop culture. Based on this summary from the Financial Times, I want to read this.

Michael Blastland’s recent book, The Hidden Half, argues that much of the variation we see in the world around us is essentially mysterious. Mr Blastland’s opening example is the marmorkrebs, a kind of crayfish that reproduces parthenogenetically — that is, marmorkrebs lay eggs without mating and those eggs develop into clones of their mothers.

Place two clones into two identical fish tanks and feed them identical food. These genetically identical creatures raised in apparently identical environments produce genetically identical offspring who nevertheless vary dramatically in their size, form, lifespan, fecundity, and behaviour. Sometimes things turn out very differently for no reason that we can discern. We might as well call that reason “luck” as anything else.

There’s a preview on Good Reads of the first chapter, which includes most of the stuff on Marmorkrebs. I’d like to point out that this is similar in some ways to an older post here on the blog about similarity and variation.

Related posts

How Marmorkrebs can make the world a better place

External links

The Hidden Half (publisher’s site)

Neil Woodford shows it can be hard to tell luck from judgment

25 May 2019

Gatzmann, 2019

Gatzmann F. 2019. DNA methylation in the marbled crayfish Procambarus virginalis. Doctoral dissertation, The Faculty of Bio Sciences, Heidelburg University. https://doi.org/10.11588/heidok.00026426


The all-female marbled crayfish Procambarus virginalis is a freshwater crayfish which is the only known obligatory parthenogen among the decapod crustaceans. Marbled crayfish are recent descendants of the sexually reproducing slough crayfish Procambarus fallax and have most likely emerged through a recent evolutionary macromutation event in P. fallax. Marbled crayfish reproduce by apomictic parthenogenesis, where oocytes do not undergo meiosis and all offspring are genetically identical clones of the mother. Nevertheless, marbled crayfish show a high degree of phenotypic variation and are a highly invasive species, where (through parthenogenesis) a single animal can establish a whole population. Moreover, they have been distributed via the pet trade and anthropogenic releases, and have formed stable populations in a variety of ecological habitats. Earlier this year, our group performed whole-genome sequencing for 11 marbled crayfish animals from different populations and countries, and found only four non-synonymous single nucleotide variances in coding regions. Since the marbled crayfish’s remarkable adaptability is not due to genetic variability, it is crucial to investigate epigenetic programming in this organism. I present here a comprehensive analysis of DNA methylation in marbled crayfish. Whole-genome bisulfite sequencing data was used to directly compare methylation patterns from multiple replicates in different tissues and from different marbled crayfish and Procambarus fallax animals. These methylation maps were integrated with RNA-seq and ATAC-seq data to comprehensively analyse the interplay between DNA methylation, chromatin accessibility, and gene expression. I found 18% of CpGs in marbled crayfish to be methylated. Repeats showed overall low methylation levels, with the exception of a single class of DNA transposons, which was ubiquitously methylated. DNA methylation was mainly targeted to the coding regions of housekeeping genes in marbled crayfish. In contrast to paradigmatic mammalian methylomes, I only observed very moderate methylation differences between tissues for both gene bodies and promoters. I did, however, identify a set of approximately 700 genes that showed a high variance in their methylation across tissues and animals. Gene body methylation was significantly inversely correlated with gene expression variability. Interestingly, the marbled crayfish shows overall lower methylation levels and higher gene expression variability than its parent species P. fallax. Since plasticity in gene expression can be a beneficial trait for adapting to new environments, this trait might contribute to the marbled crayfish’s adaptive and invasive success. The integrative analysis of DNA methylation, chromatin accessibility, and gene expression revealed that genes with highly methylated gene bodies were located in regions of poorly accessible chromatin and showed stable expression patterns. In contrast, lowly methylated genes were found in more accessible chromatin when stably expressed, and in more condensed chromatin when variably expressed. In this context, gene body methylation might function to stabilise gene expression in regions of limited chromatin accessibility. These findings broaden our knowledge of evolutionary conservation of DNA methylation patterns in invertebrates and provide novel insights on the interplay between gene body methylation, chromatin accessibility, and gene expression.

Note: Access restricted until 17 January 2020.