17 September 2021

Gutekunst and colleagues, 2021

Communications Biology
Gutekunst J, Maiakovska O, Hanna K, Provataris P, Horn H, Wolf S, Skelton CE, Dorn NJ, Lyko F. 2021. Phylogeographic reconstruction of the marbled crayfish origin. Communications Biology 4(1): 1096. https://doi.org/10.1038/s42003-021-02609-w




The marbled crayfish (Procambarus virginalis) is a triploid and parthenogenetic freshwater crayfish species that has colonized diverse habitats around the world. Previous studies suggested that the clonal marbled crayfish population descended as recently as 25 years ago from a single specimen of P. fallax, the sexually reproducing parent species. However, the genetic, phylogeographic, and mechanistic origins of the species have remained enigmatic. We have now constructed a new genome assembly for P. virginalis to support a detailed phylogeographic analysis of the diploid parent species, Procambarus fallax. Our results strongly suggest that both parental haplotypes of P. virginalis were inherited from the Everglades subpopulation of P. fallax. Comprehensive whole-genome sequencing also detected triploid specimens in the same subpopulation, which either represent evolutionarily important intermediate genotypes or independent parthenogenetic lineages arising among the sexual parent population. Our findings thus clarify the geographic origin of the marbled crayfish and identify potential mechanisms of parthenogenetic speciation.


Keywords: None provided.

29 August 2021

Tönges and colleagues 2021

Frontiers in Ecology and Evolution
Tönges S, Masagounder K, Lenich F, Gutekunst J, Tönges M, Lohbeck J, Miller AK, Böhl F, Lyko F. 2021. Evaluating invasive marbled crayfish as a potential livestock for sustainable aquaculture. Frontiers in Ecology and Evolution 9: 651981. https://www.frontiersin.org/article/10.3389/fevo.2021.651981



The marbled crayfish (Procambarus virginalis) is a recently discovered freshwater crayfish species, which reproduces by apomictic parthenogenesis, resulting in a monoclonal, and all-female population. The animals were widely distributed through the aquarium trade and have established numerous stable wild populations through anthropogenic releases. They are highly prevalent in Madagascar, where they have become a popular source of nutritional protein. As freshwater crayfish aquaculture in open systems is a thriving, but ecologically damaging global industry, alternatives are urgently needed. Although marbled crayfish are often branded by their invasive mode of reproduction, their overall invasiveness is not higher than for other cultured crayfish species. Furthermore, their resiliency and high adaptability provide a strong rationale for evaluating them for closed, and environmentally safe aquaculture approaches. Here we describe a novel population of marbled crayfish in a former German coal mining area that is characterized by acid and polluted water. Even under these adverse conditions, animals grew to sizes, and weights that are comparable to commercially farmed freshwater crayfish. Tailored feed development and laboratory testing demonstrated highly efficient feed conversion, suggesting a considerable capacity for sustainable production in closed systems. We further show that marbled crayfish meat can be readily introduced into European meals. Finally, chemical analysis of marbled crayfish exoskeletons revealed comparably high amounts of chitin, which is a valuable source for the synthesis of chitosan and bioplastics. Our results thus suggest that production of marbled crayfish in closed systems may represent a sustainable alternative for crayfish aquaculture.

Keywords: livestock • invasive species • feed conversion • chitin • sustainability • aquaculture • marbled crayfish • tailored feeds

Open access

Francesconi and colleagues 2021

Frontiers in Evology and Evolution.
Francesconi C, Makkonen J, Schrimpf A, Jussila J, Kokko H, Theissinger K. 2021. Controlled infection experiment with Aphanomyces astaci provides additional evidence for latent infections and resistance in freshwater crayfish. Frontiers in Ecology and Evolution 9: 647037. https://doi.org/10.3389/fevo.2021.647037




For 150 years the crayfish plague disease agent Aphanomyces astaci has been the cause of mass mortalities among native European crayfish populations. However, recently several studies have highlighted the great variability of A. astaci virulence and crayfish resistance toward the disease. The main aim of this study was to compare the response of two crayfish species, the European native noble crayfish (Astacus astacus) and the invasive alien marbled crayfish (Procambarus virginalis), to an A. astaci challenge with a highly virulent strain from haplogroup B and a lowly virulent strain from haplogroup A. In a controlled infection experiment we showed a high resistance of marbled crayfish against an A. astaci infection, with zoospores from the highly virulent haplogroup B strain being able to infect the crayfish, but unable to cause signs of disease. Furthermore, we demonstrated a reduced virulence in the A. astaci strain belonging to haplogroup A, as shown by the light symptoms and the lack of mortality in the generally susceptible noble crayfish. Interestingly, in both marbled crayfish and noble crayfish challenged with this strain, we observed a significant decrease of the detected amount of pathogen’s DNA during the experiment, suggesting that this A. astaci haplogroup A strain has a decreased ability of penetrating into the cuticle of the crayfish. Our results provide additional evidence of how drastically strains belonging to A. astaci haplogroup B and haplogroup A differ in their virulence. This study confirmed the adaptation of one specific A. astaci haplogroup A strain to their novel European hosts, supposedly due to reduced virulence. This feature might be the consequence of A. astaci’s reduced ability to penetrate into the crayfish. Finally, we experimentally showed that marbled crayfish are remarkably resistant against the crayfish plague disease and could potentially be latently infected, acting as carriers of highly virulent A. astaci strains.


Keywords: marbled crayfish • noble crayfish • host-pathogen co-evolution • crayfish plague • experimental infection

OPen access

25 August 2021

Fishing for Marmorkrebs

Man in pond with nets and buckets fishing for crayfish.

I missed a story from back in spring about how Marmorkrebs are being commercially fished in Berlin.

German newspaper Die Zeit reports that Marmorkrebs are an addition to an existing crayfishing operation. About a ton of Lousiana red swamp crayfish have been caught every year over the last few years. 

NPR reported on this a couple of years ago, and did not paint a rosy picture of the fishery. Despite jokes about “How can they be a problem if we can eat them?” every time I talk about invasive crayfish, not everyone likes to eat them. Few restaurants are interested, and supply is irregular.

We’ll see.

External links

Erstmals sollen Marmorkrebse ins Netz gehen

For Berlin, invasive crustaceans are a tough catch and a tough sell

09 August 2021

Lemmer and colleagues, 2020

Lemmers P, Spikmans F, Volk L. 2020. De Marmerkreeft (Procambarus virginalis), een nieuwe invasieve exoot in Limburg. Natuurhistorisch Maandblad 109: 260-266.




In terms of crayfish, the province of Limburg is a province poor in species by Dutch standards. Until 2020, only three invasive alien crayfish species were known. However, Marbled crayfish (Procambarus virginalis) were found at two isolated locations near Venlo within a short period of time in the spring of 2020. The origin and release of one of the populations could be traced via an internet vendor, who had released ten animals in 2017. A dipnet survey in 2020 at this site showed that the density was at least 30.8 specimens per 100 m of embankment. At the other site, length-frequency data suggest the species has been present since 2018. Here, the density was estimated at 5.4 individuals per 100 m of embankment. Further expansion of the populations via overland migration can be expected. It is likely that negative effects on nearby native amphibian populations will occur when no action is taken. The conclusions drawn from this study are that Marbled crayfish (1) are still offered for sale in the aquarium trade even after EU legislation, (2) are actively being released into the wild and (3) are able to establish populations in the Dutch countryside.

29 July 2021

Lemmer and colleagues, 2021

Cover to Living Nature, volume 122, issue 4.
Lemmers P, Frank Spikmans F, Koese B. 2021. Is de opmars van de marmerkreeft in Nederland nog te stuiten? De Levende Natuur 122(4): 138-140. https://delevendenatuur.nl/tijdschrift/2021-4




The first marbled crayfish in the Netherlands was recorded in 2004. The next was observed a decade later, in 2014. Since then the number of observations has increased significantly up to 14 sites in 2020, spread all over the country. The marbled crayfish became established in at least four sites of which one has been eliminated in 2020. Animals are mainly found in vegetation- rich, shallow parts of isolated waters. Other crayfish species were not present in these sites. The main introduction route of marbled crayfish is release by pet keepers. The EU Regulation 1143/2014 on Invasive Alien Species seems to have limited effect on the ongoing invasion of this species yet, as both trade and new introductions are still taking place. Swift actions, considered both cost effective and mandatory under EU legislation, are urgently needed to eliminate the species while this is still feasible.


Note: The main text of article is in Dutch. The English title is roughly, “The expansion of the marbled crayfish in the Netherlands.”

24 July 2021

Illinois State University logo.
DeMaegd ML. 2021. Physiological consequences of neuromodulation and the cellular properties that underlie them. Dissertation for Doctor of Philosophy (PhD), School of Biological Sciences, Illinois State University. https://doi.org/10.30707/ETD2021.20210719070603173187.87




Neuronal activity is a product of more than the underlying neuronal connections. Modulatory influences like changes in the animal’s environment, the animals physiological state, or the release of neuromodulators can dramatically alter neuronal activity. Modulatory influences can be beneficial for the animal because they are a source of neuronal and behavioral plasticity, and they can provide neuronal circuits with the robustness needed to continue to function in new conditions, states, or tasks.However, malfunctions of the modulatory system can disrupt neuronal activity and lead to pathologies. Predicting how modulatory influences will alter neuronal activity is challenging because the underlying cellular and circuit properties are delicately balanced and often respond in nonlinear and multifaceted ways to modulatory influences. In my thesis I address how several types of modulatory influences affect neuronal activity in the crustacean stomatogastric nervous system, and seek to characterize the circuit and cellular mechanisms that underlie them. In Chapter II I show that the activation of chemosensory pathway alters the frequency of backpropagating action potentials in a proprioceptive sensory neuron that measures muscle tension when the animal chews. These backpropagating action potentials invade the most distant regions of the proprioceptive neuron where muscle tension is encoded, including the spike initiation site and sensory dendrites. They alter the latency, the number, and the frequency of action potentials in response to muscle stimuli. When the chemosensory neurons become active, backpropagating action potential frequency decreases, thereby granting greater sensitivity to the muscle tension receptor. Since the chemosensory pathway is activated by food before the chewing starts, the modulation of backpropagating action potentials prepares the muscle receptor for future changes in muscle tension. Thus, my results demonstrate that one sensory pathway can prime another for upcoming tasks via the modulation of backpropagating action potentials. In Chapter III I show two ways that neuronal activity can be sustained during temperature modulation. First, I show that axons of different pyloric neurons maintain action potential timing between them over a large temperature range, despite their distinct morphological and intrinsic properties. I used computational model axons to determine if, and if so, how, axons with different diameters that are exposed to varying temperatures can maintain action potential timing with one another. I found that the temperature sensitivity of most ion channel properties mattered little to action potential timing. Conversely, the ratio of two Sodium channel parameters were critical: how much the maximum conductance and activation gate time constant in one axon changed with temperature relative to the other axon strongly influenced action potential timing between two. Since the ratio was critical, but not the actual values, this demonstrated that even highly temperature-sensitive ion channels can support temperature-robust action potential timing between neurons. Second, I show that acutely warming the stomatogastric ganglion by 3°C disrupts a gastric mill rhythm by diminishing the spread of electrical signals in the dendrites of the Lateral Gastric neuron (LG). I also show that a substance P-related peptide restores dendritic electrical spread and consequently the gastric mill rhythm at the warmer temperature. Specifically, the peptide rescues electrical spread through the activation of a modulatory cation current (the 'modulatory induced current' (IMI)). These data demonstrate the cellular mechanisms by which this peptide neuromodulator induces temperature-robust neuronal activity. A realization during my work on the previous chapters was that few peer-reviewed protocols exist that provide detailed and reproducible workflows of electrophysiological and molecular approaches for the study of modulatory influences. Many laboratories use 'homegrown' protocols or protocols that were inherited by word of mouth and are not widely available. This leads to a lack or reproducibility of research approaches and results and impedes the widespread use of these techniques. Chapters IV and V address these issues. In Chapter IV, I first, provide detailed protocols on how to generate action potentials in an axon using extracellular stimulation. Second, I provide a detailed protocol on how to measure action potential conduction velocity using extracellular recordings. In Chapter V, I expand on the concept of providing easily understandable and reproducible protocols to the processes of integrating genetic and molecular techniques with electrophysiological one in both lab and classroom settings. I establish a workflow that guides undergraduates or physiologists in the manual identification, confirmation, and curation of putative genes involved in neuronal function. I implement this workflow in a Course in Undergraduate Research Education (CURE) – like setting, that brings undergraduate students of all levels to actively participate in research labs by allowing students to work under supervision of graduate students and faculty mentors. The workflow outlines a efficient protocol for gene identification in marbled crayfish, clear leaning objectives, and several quality control and assessment processes that enable students to conceptualize the interconnectedness of genetics, molecular, and physiological neuroscience. By following this workflow, I identified the transcript and gene sequences for two Gamma Aminobutyric Acid (GABA) receptors subunits in the marbled crayfish (Procambarus virginalis). In addition to its educational purpose, the provided protocol serves as a first step toward integrating genetic and molecular techniques with electrophysiological ones to study the impact of receptor diversity for the cellular mechanisms of modulation in the marbled crayfish.


Keywords: None provided. 


Note: This document is embargoed until June 28, 2022.