25 June 2014

Kouba and colleagues, 2014

Kouba A, Petrusek A, Kozák P. 2014. Continental-wide distribution of crayfish species in Europe: update and maps. Knowledge and Management of Aquatic Ecosystems 413: 05. http://dx.doi.org/10.1051/kmae/2014007


Recently published astacological studies substantially improved available data on distribution of crayfish in various European regions. At the same time, spread of invasive species has been recorded, additional non-indigenous species became established in various countries, and losses of populations of native species due to crayfish plague and other negative factors were observed. We overview recent advances in this knowledge, and provide updated colour maps of the distribution of all crayfish species present in Europe. These maps are originally based on the data from the Atlas of Crayfish in Europe published in 2006 as a result of the CRAYNET project, and were further updated from more recently published reports, grey literature, and especially thanks to contributions and feedback of over 70 specialists from 32 countries. Separate maps are available for all indigenous crayfish species in Europe as well as for three most widespread non-indigenous crayfish species. Additionally, two maps give locations of known findings of crayfish species introduced to Europe after 1980. These newly established alien species have so far restricted distributions; however, the frequency of recent reports suggests that findings of such species resulting from releases of aquarium pets will further increase.

Keywords: crayfish distribution • indigenous species • invasive species • native range • maps

24 June 2014

Soedarini and colleagues, 2014

Soedarini B, van Gestel CAM, van Straalen NM, Widianarko B, Röling WFM. 2013. Interactions between accumulated copper, bacterial community structure and histamine levels in crayfish meat during storage. Journal of the Science of Food and Agriculture 94(10): 2023-2029. http://dx.doi.org/10.1002/jsfa.6519



Pollution in aquaculture areas may negatively impact edible species and threaten seafood quality and safety. The aim of this study was to determine the interaction between copper and bacteria in the aquatic habitat and their impact upon crustaceans. Marbled crayfish was chosen as a model of aquatic crustaceans and the influence of metal contamination on bacterial community structure in water used to culture crayfish and in crayfish themselves was investigated. Histamine, an allergen commonly formed by certain groups of bacteria in crustacean's edible tissue during storage, was also determined.


Copper exposure increased its concentration in crayfish meat by 17.4%, but the copper concentration remained within acceptable food safety limits. Elevated copper levels affected the bacterial community both in the water used to cultivate crayfish and in the marbled crayfish themselves. Cluster analysis of 16S rRNA-gene based microbial community fingerprints revealed that copper impacted the bacterial community in the water and in the crayfish meat. However, copper exposure reduced the formation of histamine in crayfish meat during storage by 66.3%.


Copper from the habitat appears to reduce histamine accumulation in crayfish meat during storage by affecting the bacterial community structure of the cultivation water and most likely also in the intestines of the crayfish. From a food safety point of view, copper treatment during the aqua culturing of crustaceans has a positive impact on the postharvest stage.

Keywords: copper • bacterial community structure • histamine • crayfish • storage

21 April 2014

Time to rename “crayfish” plague?

Marmorkrebs are potential vectors for crayfish plague, which is caused by Aphanomyces astaci. This pathogen devastated European crayfish since being introduced along with North American crayfish.

Now, we find out it’s not just crayfish that it can infect. A new paper by Svoboda and colleagues shows it can infect freshwater crabs, like the land crab Potamon potamios (pictured) and the Chinese mitten crab Eriocheir sinensis. The crabs appear to be more resistant to the infection than European crayfish, making the problem that the crabs are potential spreaders of disease than sufferers from it.

Hat tip to Tommy Leung.

Related post

Plague poster


Svoboda J, Strand DA, Vrålstad T, Grandjean F, Edsman L, Kozák P, Kouba A, Fristad RF, Bahadir Koca S, Petrusek A. 2014. The crayfish plague pathogen can infect freshwater-inhabiting crabs. Freshwater Biology 59:918-929.

Photo by Alastair Rae on Flickr; used under a Creative Commons license.

08 April 2014

Nefarious schemes!

Action! Adventure! Crayfish!

I always joke that the reason I went to grad school was so I could get a Ph.D., so I could be called “Doctor Zen” and sound like the villain from a bad kung fu movie.

Not a kung fu movie, but just as good.

Game designer John Wick is an acquittance of mine, who I connected with back in my grad school days. After I got my Ph.D., he took to calling me “the nefarious Doctor Zen.”

My evil namesake has been a recurring character in John’s role-playing projects (here and
there),but this is probably the biggest role yet. It includes this little bit:

The plan backfired, however, as the spider fought against Doctor Zen and his army of giant marmorkrebs (also known as marbled crayfish).

What villianous henchmen do I have now? Still very crustacean related... you will have to buy the game adventure to find out!

External links

Cartoon Action hour at Spectrum Games
Cartoon Action Hour core game
Cartoon Action Hour Season 3: Infinivaders!

01 January 2014

2013 was the second best year ever for Marmorkrebs research

Continuing an annual tradition here on the Marmorkrebs blog, we look back at what the year brought in Marmorkrebs research...

The increase in papers may be slow, but an increase it is. I like the trend...

22 December 2013

Going Grinch on Time

I should be happy that Marmorkrebs is getting attention in national media, namely Time magazine. Instead, my reaction is more like:

The annoyance starts with the title:

“Critters So Ugly They Have to Mate With Themselves”

It’s not the critters that are ugly, it’s the title. Time used to have a little more dignity, but this sounds like it came from Buzzfeed. How demeaning to call these animals “ugly,” especially when the list contains not just the pretty marbled crayfish, but the handsome Komodo dragon (which doesn’t always reproduce asexually, putting like to the “have to” portion of the title), the sleek whiptail lizard, and the amazing looking hammerhead shark (which, again, doesn’t always reproduce asexually). “Mate with themselves” suggests self-fertilization, which some animals do, but these are all cases of parthenogenesis rather than self-fertilization

The subtitle isn’t better.

Immaculate conception may be something special among humans, but in the animal kingdom, it's always been part of the mix

Science and religion are often depicted as being at war, but they are united in the desire for good fact checking. The immaculate conception is not about the virgin birth of Jesus Christ. It’s about the conception of the Jesus’s mother, Mary, free of original sin.

I’m reminded of this anecdote from Christopher Hitchens:

I made a mistake with one guy on a radio station in Seattle. I said I don’t think anyone really believes in the virgin birth and he said ‘I do.’ I said ‘you don’t really’ and he said, ‘I do, I believe absolutely in the immaculate conception.’ I told him he’d got it wrong and he said ‘What do you mean I’ve got it wrong? I’ve been a Catholic all my life.’ The immaculate conception and the virgin birth are two different concepts. He didn’t get this, but he believed in both.

The article manages to squeeze in three alternate spellings for Marmorkrebs in an equal number of paragraphs: “marmorkrebs,” and “Marmokrebs” (sic), both in a capitalized version (preferred here on the blog, following the German practice of capitalizing all nouns) and not.

And to add insult, the article is illustrated with this:

It’s not even a picture of the right species! It’s Procambarus clarkii, the common Louisiana red swamp crayfish! There are no shortage of Marmorkrebs pictures for use on this website and elsewhere. Time, you could have emailed me.

On the plus side, article does a nice job of linking to full text of the original scientific articles. And the actual text of the article, though short, is otherwise accurate.

External links

Critters So Ugly They Have to Mate With Themselves

18 December 2013

Human parthenogenesis, according to pregnant women

Christmas is the best time of the year to tell people about parthenogenesis, seeing that a story of human parthenogenesis forms a large part of Christmas tradition.

The British Medical Journal (or BMJ) has a new paper out that looks closely at reports of parthenogenesis in humans. According to Herring and colleagues, of over 7,000 young women (about 12-18) surveyed, about 0.8% of women reported pregnancy before they reported having sex.

As far as I can tell, they did not ask the women outright if they believed they got pregnant without the help of a man. They just extrapolated from whether women reported having had sex, whether they reported being pregnant, and comparing the dates. However, it seems likely that the women might have claimed virgin birth, given this interesting fact:

The virgins who reported pregnancies were more likely to have pledged chastity (30.5%) than the non-virgins who reported pregnancies (15.0%, P=0.01) or the other virgins (21.2%, P=0.007).

Also of note:

The virgins who reported pregnancy... were less likely to know how to use condoms than the non-virgins who reported pregnancy (79.6%, P=0.002).

The discussion mentions another fascinating group: the “born again virgins,” who reported having had sex early in the study, but reported themselves as virgins when surveyed again. This is actually much more common than virgin birth, accounting for about 3% of the women surveyed. This might be almost as miraculous as virgin birth.

I think there may be a few issues with self-reporting in this data set.

In addition to the interesting data, this paper also gets high points from me for referencing a Doctor Who episode in the introduction.


Herring AH, Attard SM, Gordon-Larsen P, Joyner WH, Halpern CT. 2013. Like a virgin (mother): analysis of data from a longitudinal, US population representative sample survey. BMJ 347 http://dx.doi.org/10.1136/bmj.f7102

Related post

Human parthenogenesis?

External links

Claims of virgin births in U.S. near 1 percent: study
Christmas Miracle? One In 200 US Pregnancies Reportedly Involve Virgin Mothers

Top image from here.