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

19 August 2019

Écrevisse marbrées en France

Marmorkrebs have been found in the wild in France. As of now, all I know is this tweet from Marc Collas:

The marbled crayfish (Procambarus virginalis) has just been discovered in France on the basin of the river Moselle. This is the first observation of this species in France #crayfish #ecrevisse #marmorkrebs #biodiversite

It is perhaps not surprising that Moselle River is the first location where Marmorkrebs have been found in France. The river borders Germany, which has been ground zero for Marmorkrebs introductions. It is a tributary for the Rhine River. It’s possible that the crayfish were introduced in Germany and spread into France.

More information as I learn it. The map of Marmorkrebs introductions has been updated accordingly.

External links

Marc Collas on Twitter
River Moselle

25 July 2019

Hossain and colleagues, 2019c

Hossain MS, Kouba A Buřič M. 2019. Morphometry, size at maturity, and fecundity of marbled crayfish (Procambarus virginalis). Zoologischer Anzeiger 281: 68-75. https://doi.org/10.1016/j.jcz.2019.06.005


Morphometric ratios, relationships and condition factors provide information regarding growth patterns, population dynamics and well-being of individuals in particular environments. Ecology of any species is then better understandable through life history traits and reproductive potential. The present study is aimed at exploring the morphometric and reproductive patterns of the parthenogenetic marbled crayfish, Procambarus virginalis. Marbled crayfish exhibited positive allometric growth and statistically significant common length-weight relationships. Abdomen width, claw length, width, and height increase significantly faster than the chosen most robust body size parameter, postorbital carapace length (POCL). Conversely, total length, carapace length, carapace width, and abdomen length grow proportionally slower than POCL. The condition factor was higher than the threshold value of ∼1 indicating the well-being of the crayfish used. Marbled crayfish, at their first reproduction, were recorded as long as 42.8 ± 10.8 (31.5–73.5) mm total length with a mean fecundity of 89.72 ± 56.9 (22–349) eggs. The relative fecundity (per 1 mm of POCL) of females reproducing for the first time was significantly lower compared to those reproducing repeatedly. Fecundity and relative fecundity exhibited a significant linear relationship with the carapace length and weight of mothers. As a tool for total fecundity estimation, the number of eggs on the third pair of pleopods was counted and plotted against size of mothers, and total fecundity. The number of eggs attached to the third pair of pleopods very closely correlates with the carapace length, weight and total fecundity. Based on our results, it can be concluded that abdomen width and claw growth is allometric compared to POCL which confirms the importance of these body parts. Fecundity parameters were confirmed to have a tight relationship to marbled crayfish size. Clutch size estimation can be used in future research based on the close correlation of egg counts on third pleopods and total fecundity.

Keywords: growth • reproduction • Procambarus virginalis • morphometry • fecundity