27 March 2019

Lidova and colleagues, 2019

Lidova J, Buric M, Kouba A, Velisek J. 2019. Acute toxicity of two pyrethroid insecticides for five non-indigenous crayfish species in Europe. Veterinarni Medicina 64(03): 125–133. https://doi.org/10.17221/136/2018-VETMED


Pyrethroid insecticides are highly toxic to many aquatic organisms. The aim of this study was to evaluate the toxicity of the commercial products Cyperkill 25 EC (active compound 250 g/l cypermethrin) and Decis Mega (active compound 50 g/l deltamethrin) for European non-indigenous marbled crayfish Procambarus virginalis, red swamp crayfish Procambarus clarkii, signal crayfish Pacifastacus leniusculus, spiny-cheek crayfish Orconectes limosus and yabby Cherax destructor. These data will provide a baseline for potential programmes to eradicate alien crayfish from Europe (EU Regulation No. 1143/2014; Commission Implementing Regulation No. 2016/1141) and are also relevant globally. The 96hLC50 values of Cyperkill 25 EC were 0.09, 0.17, 0.18, 0.19 and 0.30 µg/l for spiny-cheek crayfish, red swamp crayfish, marbled crayfish, signal crayfish and yabby, respectively. In the same order, the 96hLC50 values of Decis Mega were 0.76, 0.16, 0.21, 0.03 and 0.27 µg/l. The toxicity of the insecticides was similar and species-specific, possibly reflecting the size difference of the tested animals. This study shows that cypermethrin and deltamethrin are highly toxic to the tested crayfish species at low concentrations. This high sensitivity, along with the low accumulation in the food chain and short-term persistence in the aquatic environment, suggests that they are suitable biocides for eradicating crayfish in the wild. Stagnant, closed water bodies with newly emerging invaders are ideal sites for possible application, although local conditions must be considered.

Keywords: biological invasion • insecticide • cypermethrin • deltamethrin • eradication • invasive species

20 March 2019

Takahashi and colleagues, 2019

Takahashi K, Yamaguchi E, Fujiyama N, Nagayama T. 2019. The effects of quality of shelters and prior residence on marmorkrebs (marbled crayfish). Journal of Experimental Biology 222(6):. https://doi.org/10.1242/jeb.197301


Many animals fight over a limited valuable resource. In marmorkrebs (marbled crayfish), large animals usually defeated small opponents but they were frequently beaten by small opponents who were shelter owners. A prior residence effect of marbled crayfish was analyzed quantitatively. More than 2 hr of residency in a shelter was sufficient for small owners to defeat large intruders. Small animals that stayed in a shelter for 24 hr still tended to win following removal of the shelter 10 min before pairing with large intruders, but 2 hr residents were occasionally beaten by large intruders without the support of shelters during pairings. The prior residence effect thus developed depending on the time of residency. To clarify whether the strength of the prior residence effect was affected by the quality of a shelter, large and small owners with different combinations of two high and low quality of shelters were paired. When both large and small owners possessed a high quality shelter, the frequency of agonistic bouts was reduced. Even if agonistic bouts occurred, the win frequency of small owners was almost equal to that of large owners. Thus, the residence effect on small owners was sufficiently strong to overcome the physical disadvantage of small animals to large opponents. By contrast, small owners of low quality shelters were frequently beaten by large owners with the shelters of same or better quality. We conclude that the outcomes of fighting over the resource shelter are highly dependent on both the perception of shelter quality and body size differences.

Keywords: agonistic encounter • owner: intruder • perception • winner effect • residence effect

18 March 2019

International Crayfish Conference 2019

The International Conference on Crayfish will be in Europe this year, organized by Blue Centre Gotland, Swedish University of Agricultural Sciences. and University of Eastern Finland. This conference is open to both researchers and crayfish farmers.

For more information, contact Gunilla Rosenqvist (gunilla.rosenqvist@geo.uu.se) or Lennart Edsman (Lennart.edsman@slu.se).

External links

Internationell kräftkonferens 27 - 30 augusti 2019

07 March 2019

Bradshaw, 2019

Bradshaw L. 2019. The genetic authentication of Malagasy crayfish samples. South Carolina Junior Academy of Science. 270. https://scholarexchange.furman.edu/scjas/2019/all/270


The marbled crayfish (Procambarus virginalis) is a relatively new species that emerged by macromutation nearly 30 years ago from Procambrus fallax. Despite its short existence, it has already become an invasive species because of its ability to reproduce clonally and its environmental adaptability. The marbled crayfishes’ high adaptability allows it to thrive in diverse conditions throughout the globe. It is very important to correctly identify marbled crayfish because, to do epigenetic research with them, we need to know the epigenetic profile. This experiment analyzed two Malagasy crayfish samples to test if they were Procambarus virginalis. This work was necessary because it is the only way to distinguish between different crayfish species besides morphology which is subjective. DNA was isolated from the abdominal tissue of 2 unknown crayfish samples, analyzed by PCR, and compared to known DNA reference sequences. The results for crayfish #1 were inconclusive because the insert was not incorporated by the plasmid, but it was confirmed that crayfish #2 was Procambarus virginalis. Future work on the marbled crayfish will be to help establish a methylome sequence. This methylome sequence will show average methylations to the DNA, helping further understand the epigenetics of clonal tumor evolution.

Keywords: None provided.

Banned in Japan?

The Japanese newpaper The Mainichi is reporting that Marmorkrebs could soon be added to Japan’s list of “Invasive Alien Species.”

The article notes that there have been a couple of isolated cases of Marmorkrebs found in the wild in Japan (as noted on the map of introductions). The article provides the first confirmation I know of – unsurprising though it is – that Marmorkrebs are readily available in the pet trade there.

Looking at the Ministry’s page on invasive species, crayfish are already regulated to some degree. The PDF of regulated species say all crayfish (“Any species of the families Astacidae, Cambaridae, and Parastacidae”) are “Required to have a Certificate Attached during their importation in order to verify their types.” But this does nothing once a species is in the national pet trade and being distributed within Japanese borders.

Marmorkrebs would join all the species of Astacus and Cherax, the signal crayfish (Pacifastacus leniusculus), and the rusty crayfish (Faxonius rusticus, still listed as Orconectes in the Japanese documents) as an invasive.

External links

Environment ministry plans to add marbled crayfish to list of invasive species

05 March 2019

Stara and colleagues, 2019

Stara A, Kubec J, Zuskova E, Buric M, Faggio C, Kouba A, Velisek J. 2019. Effects of S-metolachlor and its degradation product metolachlor OA on marbled crayfish (Procambarus virginalis). Chemosphere 224: 616-625. https://doi.org/10.1016/j.chemosphere.2019.02.187


Increasing production of energy crops in Europe, mainly maize and rapeseed, has altered patterns of pesticide use in recent decades. The long-term effects of S-metolachlor (S-M) and of its metabolite metolachlor OA (M-OA) at the environmentally relevant concentration of 4.2 μg  L−1 and at 42 μg  L−1 (ten-fold concentration) on marbled crayfish (Procambarus virginalis) were evaluated in a 28-day exposure and after a subsequent 28-day recovery period. Indicators assessed were behaviour; biochemical haemolymph profile; oxidative and antioxidant parameters of gill, hepatopancreas, and muscle; and histology of hepatopancreas and gill. Results showed biochemical haemolymph profile (lactate, alanine aminotransferase, aspartate aminotransferase, inorganic phosphate), lipid peroxidation in hepatopancreas, and antioxidant parameters (catalase, reduced glutathione, glutathione S-transferase) of hepatopancreas and gill of crayfish exposed to S-M and M-OA to significantly differ from controls (P < 0.01). Antioxidant biomarker levels remained different from controls after a 28-day recovery period. Differences in behaviour including speed of movement and velocity, and histopathological damage to gill and hepatopancreas were associated with S-M and M-OA exposure and persisted after 28 days in S-M- and M-OA-free water. Results suggest harmful effects of low concentrations of S-M and its metabolite M-OA on non-target organisms and provide information for assessing their effects at environmentally relevant concentrations.

Keywords: herbicide • metabolite • crustacean • biomarkers • histology • recovery