07 November 2019

Linzmaier, 2019

Linzmaier SM. 2019. Ecology and evolution in novel communities: The marbled crayfish and its interaction partners. Doctoral thesis, Department of Biology, Chemistry and Pharmacy, Freie Universität Berlin. http://dx.doi.org/10.17169/refubium-25647


Ecosystems worldwide are undergoing drastic changes caused by the intentional and unintentional transfer of species between them. This anthropogenic process has accelerated within the last centuries, creating novel ecosystems which harbor species assemblages devoid of a shared evolutionary history. When novel organisms interact with their new environment and the members of the invaded community, they often exhibit different or even new traits compared to established species. These interactions can thus be difficult to predict, and they can have far-reaching consequences on biotic and abiotic components of the ecosystem. Especially differences in trophic interactions and behaviors can cause the most severe repercussions of species invasions. Therefore, a deeper understanding of the mechanisms underlying the invasion process informs general ideas of community assembly and can help predict potential invasions and the risks associated with it. To gain an understanding of the interactions within novel communities, this dissertation combines empirical and theoretical approaches from the fields of community, invasion and behavioral ecology. The first chapter of the thesis presents a framework for risk assessments of novel organisms based on trophic interactions. A fundamental ecological principle, the functional response (i.e. the per-capita consumption rate as a function of resource density) is used to identify and quantify trophic traits of novel organisms linked to invasion success. The new approach presented in this chapter prioritizes and selects subsets of trophic links within the system in question and demonstrates the application of functional responses while including multiple potential interaction partners in the invaded system. The invasion of marbled crayfish Procambarus virginalis into Germany and a resident non-native congener (spiny-cheek crayfish Faxonius limosus) are used to illustrate the framework. However, the framework is applicable to a variety of novel organisms and invasion scenarios. The second chapter implements the framework from Chapter 1 by executing the aforementioned example within a laboratory study and the parameterization of a mechanistic functional response model. Predator-prey interactions between the crayfish species and individuals feeding on a key aquatic primary consumer (Dreissena spp.) are examined in great detail to mechanistically explain trophic-trait differences. Data from video-recordings of foraging and feeding events are used to model and predict functional responses from independently derived predation parameters. In addition, modeled and empirically observed functional responses are linked to individual behavioral traits. Furthermore, this chapter demonstrates and discusses the explanatory power of the predation parameters on functional responses. The third chapter assesses and compares behavioral traits that are important for the invasion success of crayfish species. Individual traits related to interspecific interactions – such as agonistic behavior between two crayfish and the response to predators, but also activity, which is related to foraging – are tested therein. In addition, correlations between behaviors, or so-called behavioral syndromes, are evaluated. This chapter also compares behavioral differences between naïve aquarium and naturalized individuals of marbled crayfish, and discusses the overall importance of the observed behavioral traits for novel communities. In the fourth and final chapter, the prey-choice of marbled crayfish compared to that of established spiny cheek crayfish from field sites were investigated in the laboratory and contrasted with diet data from invaded lakes. Also, the trophic position and trophic niche size are determined to assess the ecological function of each species. To understand what resources the species use and which prey items or resources are mostly impacted, preferences and consumption rates were measured in predator-free environments and computed from stable isotopes of lake ecosystems. This part of the dissertation delivers insights into the in situ impacts of marbled crayfish in invaded food webs by highlighting particularly important interactions in an ecosystem context. My thesis provides a novel interaction framework applicable for risk assessments of novel organisms (Chapter 1). It advances fundamental principles of ecology and invasion biology by providing a detailed, mechanistic examination and modeling of predator-prey interactions (Chapter 2), including the behavioral aspects (Chapter 3) and the food web effects (Chapter 4) of the novel, invasive marbled crayfish and a functionally similar comparator species, the spiny-cheek crayfish.

Keywords: ecological novelty • functional responses • freshwater crayfish • behavioral syndromes • biological invasions • over-invasions • trophic niche • predator–prey interactions

Sciency thinking on Marmorkrebs

The Sciency Thoughts blog by Joe Bauwens has a nice summary of a paper on Marmorkrebs in Madagascar from earlier this year. Go check it out!

External links

Assessing the impact of the introduced and highly invasive Marbled Crayfish on freshwater ecosystems in Madagascar.

15 September 2019

Mauvisseau and colleagues, 2019

Mauvisseau Q, Tönges S, Andriantsoa R, Lyko F, Sweet M. 2019. Early detection of an emerging invasive species: eDNA monitoring of a parthenogenetic crayfish in freshwater systems. Management of Biological Invasions 10(3): 449–460. https://doi.org/10.3391/mbi.2019.10.3.04


Procambarus virginalis, also known as the Marmorkrebs is a highly invasive crayfish species characterized by parthenogenetic reproduction. As conservation management plans rely on the accuracy of the presence and distribution information of invasive species, a reliable method is needed for detecting such species in aquatic systems. We developed and validated a qPCR-based assay for monitoring P. virginalis at low abundance, by detecting their eDNA traces left in freshwater systems. We were able to implement this new assay in-situ at two separate lakes in Germany, where the crayfish were known to be present. Furthermore, we did not detect the pathogenic fungus Aphanomyces astaci in the locations where the Marmorkrebs were detected. We conclude that the use of eDNA is therefore a reliable tool for the early detection of this “perfect invader”.

Keywords: eDNA detection • lakes • Marmorkrebs • crayfish plague • qPCR

09 September 2019

Forum Flusskrebse theme issue

Forum Flusskrebse is a German-language society for the study of crayfish. They have a regular periodical (Google Translate calls it a “newspaper”). Issue #30 has three articles on Marmorkrebs.

• Genetically equal and yet different: advantages and benefits of marble crayfish for research
Genetisch gleich und doch verschieden: Vorteile und Nutzen des Marmorkrebses für die Forschung

• The zoo trade as an entry path for invasive species: what we can learn from marble crayfish
Der Zoohandel als Einschleppungspfad für invasive Arten: Was wir vom Marmorkrebs lernen können

• Environment-induced plasticity of a parthenogenetic crayfish: Population ecology of the marble crayfish Procambarus virginalis in southwestern Germany
Umweltinduzierte Plastizität eines parthenogenetischen Flusskrebses: Populationsökologie des Marmorkrebses Procambarus virginalis in Südwestdeutschland

The English translations are courtesy of Google Translate and may not be entirely accurate, but I hope they give a passable idea of what the work is about.

This periodical is available in the society’s shop for 10€.

Hat tip to Günter Vogt.

External links

Forum flusskrebse 

28 August 2019

Ercoli and colleagues, 2019

Ercoli F, Kaldre K, Paaver T, Gross R. 2019 First record of an established marbled crayfish Procambarus virginalis (Lyko, 2017) population in Estonia. BioInvasions Records 8(3): 675-683. https://doi.org/10.3391/bir.2019.8.3.25


Invasive marbled crayfish Procambarus virginalis (Lyko, 2017) is spreading alarmingly fast across European countries and beyond. Early maturation, parthenogenetic reproduction mode and high growth rate contribute to a high potential invasiveness. Marbled crayfish can pose severe effects on native communities impacting the native crayfish populations being carrier of the crayfish plague disease caused by Aphanomyces astaci. Here we report the first record of marbled crayfish in Estonia. In total, 104 individuals were found in the artificially warm outflow channel of the cooling system of Balti Power Plant, entering to the water reservoir of the River Narva. Molecular analyses confirmed the morphological identification of captured specimens as a marbled crayfish. Four out of six marbled crayfish individuals exhibited the presence of crayfish plague agent, though at very low level. This suggests that marbled crayfish can potentially be a new vector of crayfish plague in Estonian freshwater ecosystems containing native noble crayfish Astacus astacus populations. Monitoring and eradication actions are urgently needed not only in the outflow channel where the species was found but in the whole water reservoir and River Narva itself.

Keywords: invasive crayfish • NICS • crayfish plague • reservoir • artificial refuge trap • mitochondrial DNA

20 August 2019

Haubrock and colleagues, 2019

Haubrock PJ, Kubec J, Veselý L, Buřič M, Tricarico E, Kouba A. 2019. Water temperature as a hindrance, but not limiting factor for the survival of warm water invasive crayfish introduced in cold periods. Journal of Great Lakes Research 45(4): 788-794. https://doi.org/10.1016/j.jglr.2019.05.006


The success of non-native species establishment depends on various abiotic and biotic factors that determine the outcome of an introduction event. Limiting temperature ranges have been studied for various non-native species; however, such previous assessments of species-specific temperature thresholds may be inadequate. Because several non-native crayfish species prefer warmer water temperatures, introductions were generally assumed to occur during preferable, warmer periods. However, despite the generality, traditionally considered ‘warm-water’ species are gradually appearing in new habitats, which were previously considered too cold for successful establishment. Newly discovered overwintering abilities of these species are likely related to the winter stratification in lentic ecosystems, which maintain tolerable conditions. To understand better the survivability of two such non-native species, red swamp crayfish Procambarus clarkii and marbled crayfish Procambarus virginalis individuals were abruptly subjected to a thermic shock which lowered the water temperature from 20°C (room temperature) to 6°C, 4°C and 2°C, thus mimicking the release by pet owners during various phases of winter. The survival rate and foraging activity were monitored for up to 98 days. Procambarus clarkii showed a considerable higher survival rate at low temperatures (4°C, 2°C) compared to that of P. virginalis with neither sex nor size differences evident. Our findings reveal the ability of warm water invaders to withstand a shock during introduction at low temperature periods without acclimation. Considering these newly discovered shifts in physiological limitations, particularly for the red swamp crayfish, this may indicate a higher threat for areas with colder conditions.

Keywords: mortality • pet trade • biological invasion • thermocline

Guo and colleagues, 2019

Guo W, Kubec J, Veselý L, Hossain MS, Buřič M, McClain R, Kouba A. 2019. High air humidity is sufficient for successful egg incubation and early post-embryonic development in the marbled crayfish (Procambarus virginalis). Freshwater Biology 64(9): 1603-1612. https://doi.org/10.1111/fwb.13357


  1. Severe weather events, such as long‐term droughts, are challenging for many freshwater species. To survive drought, freshwater crayfish tend to inhabit shelters or burrows where they can remain in contact with water or high humidity environments. However, it is not known whether embryogenesis or post‐embryonic development can occur without free standing water.
  2. To address this question, three experiments were conducted using artificial burrows with high air humidity and using marbled crayfish (Procambarus virginalis Lyko, 2017) as a model species. Marbled crayfish are capable of parthenogenetic reproduction, burrow extensively and are able to travel long distances over land. In the first experiment, ovigerous females were transferred to simulated burrows without free water, but with high air humidity. A control group of females were kept in burrows with free water. Successful hatching was achieved in both groups.
  3. In the second experiment, ovigerous females were transferred to simulated burrows with no free water but high air humidity and post‐embryonic development were observed. Following successful hatching, offspring moulted to the second developmental stage (stage 2 juveniles). Stage 2 juveniles remained viable without free water for 20 days, but further development was not observed. However, when some of these stage 2 juveniles were placed back into fully aquatic conditions (experiment 3), they moulted to stage 3 within 4 to 8 days.
  4. These results demonstrated the ability of marbled crayfish to undergo terminal phases of embryogenesis, including hatching, as well as early post‐embryonic development under high air humidity conditions only. Post‐embryonic development was suspended in the absence of free water, and successfully resumed when re‐immersed.
  5. This similar ability to tolerate drought‐like conditions during post‐embryonic development may also occur in other crayfish species, especially primary burrowers. This unprecedented life history trait may be crucial for inhabiting ecosystems with rapidly changing water regimes. In drying climates, it may confer advantages on some crayfish species (including some invasive species) over others.

Keywords: burrow • drought • hyporheic dweller • macroinvertebrate • ontogeny