Tönges and colleagues 2021

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

Abstract

 

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

Francesconi and colleagues 2021

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

 

Abstract

 

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

Fishing for Marmorkrebs

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

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.

 

Abstract

 

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.