17 May 2019

First Marmorkrebs on Twitter!

Set the wayback machine to a decade ago. Ten years ago, Marmorkrebs debuted on Twitter. The First to Tweet account says:

The first to tweet ‘Marmorkrebs’ was @DoctorZen in 2009!

It is a bit of a cheat, though, since the tweet was about this blog more than Marmorkrebs.

Enjoying that Marmorkrebs.blogspot.com was a finalist for Open Laboratory 2008.

16 May 2019

Marmorkrebs in the Middle East

I heard from astacologist Chris Lukhaup today that marbled crayfish are now in the rivers and ponds on Israel. Yes, plural.

This represents another signifcant expansion of Marmorkrebs across the globe, as it is the first report in western Asia. 

I don’t have more details at this time as to location and such, but am sure it will be forthcoming. I have updated the map of Marmorkrebs introductions with a generic pin for all of Israel at this time.

Thanks to Chris for giving me permission to share this.

23 April 2019

Veerappan 2019

Veerappan V. 2019. The effects of peptide neuromodulators on temperature responses in the crustacean nervous system. University of Illinois University Research Symposium: 351. https://ir.library.illinoisstate.edu/rsp_urs/351


Temperature perturbations affect neuronal activities by altering the intrinsic ionic conductances that underlie the electrical properties of neurons. High temperatures can lead to an excessive increase in conductance and a shunt of neuronal responses, which decreases cell excitability and eventually causes a loss of neuronal activity. Surprisingly, though, many neuronal circuits continue to function in spite of these challenges, suggesting that they possess compensatory mechanisms to overcome the detrimental effects of temperature. In the crustacean stomatogastric ganglion even small temperature increases lead to loss of neuronal activity. Previous studies have shown that the presence of a neuropeptide released from modulatory projection neurons rescues the neuronal activity by counterbalancing the excessive conductance increase caused by high temperatures. However, it is not clear whether this rescue mechanism is common to many neurons or an idiosyncrasy of the stomatogastric system. We address this question using primary cell cultures derived from neural tissue of the marbled crayfish, Procambarus virginalis. Cell cultures allow us to characterize the responses of crustacean neurons from many different origins independent from circuit influences, and to test their responses to temperature challenges. Because neuropeptides are ubiquitously present in the nervous system and marbled crayfish survive large temperature fluctuations with seemingly few effects on behavioral effects, we hypothesize that most, if not all crustacean neurons have the ability to overcome temperature perturbations and that peptide modulators enable them to do so. To test our hypothesis we are challenging cultured neurons with temperature changes and analyze (1) the collective neuronal responses by measuring field potentials and (2) individual and collective neuronal responses using calcium imaging. Neurons will be raised under constant temperature conditions for a prolonged time period to exclude homeostatic adaptations of their temperature responses. To analyze how far cultured neurons withstand temperature fluctuations, we will compare their activities before and during a transient increase in temperature. We will determine the role of peptide modulators in temperature compensation by subjecting neurons to different modulators and observing changes in their temperature responses. We predict that, like neurons in the stomatogastric ganglion, cultured neurons can withstand fluctuations in temperature better in presence of neuromodulators. This would indicate the essential role played by the peptide neuromodulators in restoring neuronal activity when faced with changes in temperature.

Keywords: None provided.

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.