06 November 2018

Marmorkrebs in silhouette

In case you need a representation of a marbled crayfish to pop into one of your figures, or any other kind of organism, try Phylopic. While I was tooling around there, I found this image of Marmorkrebs by Kamil S. Jaron:

Presumably, a couple of legs are being held under the body. And I wouldn’t trust this page for taxonomic information, as the authority given for Marmorkrebs is incorrect. Not sure how easy it is to fix that.

Update, 9 November 2018: It’s fixed on both counts! Woohoo!

New link for new image is here.

External links


09 October 2018

Gatzmann and colleagues, 2018

Gatzmann F, Falckenhayn C, Gutekunst J, Hanna K, Raddatz G, Carneiro VC, Lyko FJE. 2018. The methylome of the marbled crayfish links gene body methylation to stable expression of poorly accessible genes. Epigenetics & Chromatin 11(1): 57. https://doi.org/10.1186/s13072-018-0229-6


Background: The parthenogenetic marbled crayfish (Procambarus virginalis) is a novel species that has rapidly invaded and colonized various different habitats. Adaptation to different environments appears to be independent of the selection of genetic variants, but epigenetic programming of the marbled crayfish genome remains to be understood.

Results: Here, we provide a comprehensive analysis of DNA methylation in marbled crayfish. Whole-genome bisulfite sequencing of multiple replicates and different tissues revealed a methylation pattern that is characterized by gene body methylation of housekeeping genes. Interestingly, this pattern was largely tissue invariant, suggesting a function that is unrelated to cell fate specification. Indeed, integrative analysis of DNA methylation, chromatin accessibility and mRNA expression patterns revealed that gene body methylation correlated with limited chromatin accessibility and stable gene expression, while low-methylated genes often resided in chromatin with higher accessibility and showed increased expression variation. Interestingly, marbled crayfish also showed reduced gene body methylation and higher gene expression variability when compared with their noninvasive mother species, Procambarus fallax.

Conclusions Our results provide novel insights into invertebrate gene body methylation and its potential role in adaptive gene regulation.

Keywords: None provided.

05 October 2018

Anastácio and colleagues, 2019

Anastácio PM, Ribeiro F, Capinha C, Banha F, Gama M, Filipe AF, Rebelo R, Sousa R. 2019. Non-native freshwater fauna in Portugal: A review. Science of The Total Environment 650: 1923-1934. https://doi.org/10.1016/j.scitotenv.2018.09.251


We present the most updated list of non-native freshwater fauna established in Portugal, including the Azores and Madeira archipelagos. This list includes 67 species at national level but corresponds to 84 species records, of which 53 are in the mainland, 23 in the Azores and 8 in Madeira archipelagos. We also discuss the progression of the cumulative number of introductions since 1800 and identify the most probable vectors of introduction, main taxonomic groups and their regions of origin. Furthermore, we review the existing knowledge about ecological and economic impacts, invasion risk and potential distribution of invaders, under present and future climatic conditions, and the applied management actions, including the production of legislation. Along the 20th century the number of successful introductions increased at an approximate rate of two new species per decade until the beginning of 1970s. Since then, this rate increased to about 14 new species per decade. These introductions were mainly a result of fisheries, as contaminants or for ornamental purposes. Fish and mollusks are the taxonomic groups with more established species, representing more than half of the total. Most species (>70%) are native from other regions of Europe and North America. Studies about ecological or socioeconomic impacts are more common for fish, crustaceans and mollusks. Impacts for most amphibians, reptiles and mammals are not thoroughly studied. A few studies on the impacts and management actions of health-threatening mosquitoes are also available. The potential distribution in the Portuguese territory was modelled for 26 species. Only a minority of these models provides projections of distributions under scenarios of future climate change. A comparison of the Portuguese and EU legislation shows large discrepancies in the invasive species lists. Using the EU list and a ranking procedure for the national context, we identify freshwater species of high national concern for which actions are urgently needed.

Keywords: invasions • exotic species • Iberian Peninsula • risk assessment • inland waters • aquatic systems

25 September 2018

Göpel and Wirkner, 2018

Göpel T, Wirkner CS. 2018. Morphological description, character conceptualization and the reconstruction of ancestral states exemplified by the evolution of arthropod hearts. PLOS ONE 13(9): e0201702. https://doi.org/10.1371/journal.pone.0201702


Arthropods are the most species-rich taxon within Metazoa and have gone through major evolutionary changes with regard to body organization. Arthropod hearts and their associated vascular systems are thus morphologically highly disparate: while some arthropods exhibit very powerful hearts and complex vascular systems, other arthropods do not possess any kind of vascular system or heart at all. A comprehensive study investigating the structure of arthropods hearts has never been undertaken. In this study, we therefore investigate the hearts of 34 species from all major arthropod groups using various imaging techniques (confocal laser scanning microscopy, micro-computed tomography, histology) and describe them by addressing different aspects of heart morphology, e.g. the structure of the myocard or the composition of ostia. In a next step, we conceptualize 18 characters related to heart morphology and their respective character states and–using additional data from the literature–score a matrix for a total of 45 species from 38 supraspecific taxa. We map the characters onto prevailing phylogenetic hypotheses and perform parsimony-based ancestral state reconstruction to trace the evolutionary transformations undergone by arthropod hearts. An exploration of the character concepts (as explanatory hypotheses) reveals ontological peculiarities of character statements that clearly distinguish them in terms of ontological status from descriptive statements (i.e. descriptions of morphemes). The implications of these findings influence the interpretation of ground patterns as explanations. This first phylogenetic approach to heart morphology in the arthropod ground pattern reveals numerous new putative synapomorphies and leads to a reconsideration of the morphology of circulatory systems in early arthropods. Hypotheses on the evolution of hearts in (Pan-) Arthropoda are illustrated and discussed.

Keywords: None provided.

24 September 2018

Crayfish crimes 2

I mentioned a couple of weeks back that an American man had been convicted for selling and exporting crayfish as pets. Another case came to attention recently. An Australian man was convicted and fined AUD$8,550 for catching the world’s largest freshwater invertebrate, Astacopsis gouldii. The crayfish is threatened and protected by law.

I mention this because protecting invertebrates is hard, and law enforcement on this sort of issue is rare. It’s encouraging to see.

Related posts

Crayfish crimes

External links

Largest ever fine for poaching giant freshwater crayfish

21 September 2018

Linzmaier and colleagues, 2018

Linzmaier SM, Goebel LS, Ruland F, Jeschke JM. 2018. Behavioral differences in an over-invasion scenario: marbled vs. spiny-cheek crayfish. Ecosphere 9(9): e02385. https://doi.org/10.1002/ecs2.2385


New species often invade ecosystems already dominated by previous invaders. Ornamental freshwater crayfish, particularly parthenogenetic marbled crayfish (Procambarus virginalis), increasingly establish in European water bodies where they interact with resident native and non-native species. Behavioral traits and behavioral syndromes can influence the outcome of these species interactions. The behavior of non-native crayfish is often studied in notorious invaders but rarely in new and emerging species, although those provide the best opportunity for management. Activity, aggressiveness, and boldness have repeatedly been associated with invasion success and species displacement. Further, crayfish can adapt their behavior after they have established in the new range. We investigated whether marbled crayfish can displace the widely established spiny-cheek crayfish (Orconectes limosus). Specifically, we compared their behavioral traits and evaluated whether these traits differ, using marbled crayfish populations from aquaria and the field and spiny-cheek crayfish from the field.We staged agonistic encounters, measured activity levels, and recorded the response to a simulated threat of both species and both origins (field and aquarium) in laboratory trials. We found that in agonistic encounters, marbled crayfish were on average more aggressive than spiny-cheek crayfish, even against larger opponents. Aggressiveness and activity were positively correlated, which is indicative for an aggression syndrome. Marbled crayfish from the field were less active than those from aquaria, but there was no difference in aggressiveness. Marbled crayfish often froze in response to a simulated threat, whereas spiny-cheek crayfish reacted either offensively or defensively. These results from the laboratory illustrate potentially important behavioral mechanisms behind crayfish over-invasions and show behavioral plasticity in a species where all known individuals are genetically identical. To better understand the invasion process in nature, the species’ reproductive biology and interactions with other members of the community should be considered. We conclude that the recent success of marbled crayfish in establishing new populations could be influenced by their behavioral flexibility and their potential to competitively persist in the presence of established invasive crayfish.

Keywords: aggression • behavioral flexibility • behavioral syndromes • behavioral variability • biological invasions • freshwater crayfish • shelter use • threat response

19 September 2018

The Maltese crayfish: A dozen invaded European countries

It was Germany, then Italy, then the Netherlands, then Hungary, then Croatia, then Slovakia, then Romania, then Sweden, then the Ukraine, then the Czech Republic, then Estonia, and now Malta.

Malta makes it an even dozen European countries where Marmorkrebs have been found in outdoors, according to a paper in press from Deidun and colleagues. This is not a few stray individuals, either. Some sites (visited in 2016 and 2017) had hundreds of individuals. I will add the paper to the collection of abstract on the blog once the final paginated version is published.

I have updated the map of Marmorkrebs introductions accordingly.

My only consolation is that at some point, I’m going to run out of European countries to add to the list. Marmorkrebs will be in all of them.


Deidun A, Sciberras A, Formosa J, Zava B, Insacco G, Corsini-Foka M, Crandall KA. Invasion by non-indigenous freshwater decapods of Malta and Sicily, central Mediterranean Sea. Journal of Crustacean Biology: in press. http://dx.doi.org/10.1093/jcbiol/ruy076

External links

Alien crayfish invade Malta’s valleys and watercourses
Alien crayfish have invaded Malta’s valleys, study finds