21 November 2020

Citizen science detected Marmorkrebs

Observations.org logo
I’d read a lot of news articles in late October about the discovery of Marmorkrebs in Brussels. Ariana Remmel managed to add an important detail I hadn’t seen before: that the Marmorkrebs were spotted as the result of citizen science.

A research team led by Kevin Scheers... first realized there might be a problem when he saw a marbled crayfish photo misidentified on a citizen science website called Waarnemingen.be.

The site is a local iteration of Observations.org, a website for recording observations of species in nature.

This is important, because as Marmorkrebs becomes more and more widespread, I am deeply worried researchers will lose interest in documenting where they are. Good monitoring is important to management and without it, the spread of Marmorkrebs – already difficult to detect – will be even harder.

External links

Turkey troubles and cantankerous crustaceans

14 November 2020

Why sex? (Why not?)

Quanta Magazine has a nice article about the evolution of sexual reproduction. I had hoped it might also focus on cases where sex is lost, as in Marmorkrebs, but worth a peek regardless.

External links

Why Sex? Biologists Find New Explanations.

13 November 2020

Laurenz and colleagues 2020

Water, Air, & Soil Pollution cover
Laurenz J, Lietz L, Brendelberger H, Lehmann K, Georg A. 2020. Noble crayfish are more sensitive to terbuthylazine than parthenogenetic marbled crayfish. Water, Air, & Soil Pollution 231: 548. https://doi.org/10.1007/s11270-020-04921-3




We investigated the sensitivity of two freshwater crayfish species (Astacus astacus and Procambarus virginalis) during embryonic development to chronic exposure to the herbicide terbuthylazine under laboratory conditions. The assessed parameters included time of embryonic development, survival rate, hatching weight and histopathology of hepatopancreas. LC50 (median lethal concentration) and ED50 (median effective concentration) were estimated. We were able to determine effects of terbuthylazine for every investigated parameter. For noble crayfish, the LC50 value after 45 days was 0.11 mg/L, and the histology of the hepatopancreas showed effects starting from 0.025 mg/L. Other parameters revealed effects starting at concentrations of 1.6 mg/L for weight and 6.4 mg /L for embryonic development time and hatching rate. Marbled crayfish only showed effects concerning the hatching rate and survival rate at concentrations without a clear dose-effects curve. As a conclusion, our data shows the risk of terbuthylazine in existing concentrations in freshwater ecosystems to non-target organisms and also the need of toxicological studies on directly affected species in addition to the use of model organisms.


Keywords: marbled crayfish • noble crayfish • juveniles • terbuthylazine • embryonic



07 November 2020

Lost in translation

"The Interpreter" movie poster
It’s been a busy few weeks here on the Marmorkrebs newswatch. 


Three new countries added to the list of known introductions: Belgium, Poland, and the island of Taiwan.


One country banning most crayfish, including marbled crayfish: Japan.


What is nagging me after these last few weeks is this question: how much am I missing?


The news about crayfish in Poland had been out for some time. I missed it because it wasn’t in English. I stumbled upon when I was updating the marbled crayfish Wikipedia page


The news about Marmorkrebs in Taiwan and new regulations in Japan could have easily slipped by me if they hadn’t been reported on English news websites.

I have strong suspicions that there are many more introduced populations out there that aren’t getting into the scientific literature, because marbled crayfish introductions have happened so much that they aren’t considered notable. And I’m not finding them, because they are not being reported in English.

I don’t think I can set up Google alerts for every language, and I'm not even sure what people would call Marmorkrebs in most languages. So I don’t know how to fix this yet.

06 November 2020

Marmorkrebs’ second Asian invasion

Map showing location of Taiwan island in Asia

Mere days after Marmorkrebs made international news by invading a cemetery in Belgium, they appear set to take over a park in Taiwan Island. 


This is only the third time Marmorkrebs have been reported in Asia, and this seems to be the most substantial population so far. Previous discoveries of Marmorkrebs in Japan consisted of only single individuals.


There are more individuals in this one bucket fron Daan Forest Park than have been discovered in all of Japan.


Perhaps the one piece of good news is that it sounds like these are isolated, managed park ponds. If authorities want to get serious, they might be able to remove all of them (emphasis added):


Wang Shu-ya, director of the Youth Park Management Office said that park staff have been cooperating with the Friends of Da’an Park Foundation to trap the crayfish. Wang said that the situation has improved slightly, however, they have not ruled out the possibility of draining the ponds in the future to completely remove the pests.

One interesting trend I am starting to notice in news coverage is the use of the term “mutant.” Strictly speaking, yes, Marmorkrebs are mutants. But many other similar organisms are not described that way. 


An all-female species of whiptail lizards are not called “mutants.” 


Amazon mollies, reasonably popular aquarium fish, are all female and have even weirder reproduction than Marmorkrebs (sperm stealing?!) and they aren’t called “mutants.” 


What is it about Marmorkrebs that leads people to describe them this way?

The main news article is quite good, although I am surprised it uses the old species name and not Procambarus virginalis, which has been widely adopted by the community.


I have updated the map of Marmorkrebs introductions.


External links


Mutant invasive crayfish found infesting ponds in Taipei City park


Daan Forest Park crisis! Invasion of exotic species "Marbled crayfish"  (Video in Chinese; title loosely translated)

02 November 2020

Marmorkrebs banned in Japan

Flag of Japan
A wire story from Jiji Press is reporting that Marmorkrebs — along with many other nonnative crayfish — are being effectively outlawed in Japan.


Raising and selling of all nonnative species of crayfish, excluding red swamp crayfish, became prohibited in principle in Japan on Monday... Species newly added to the list are foreign crayfish belonging to four groups, including marbled crayfish, which reproduce without fertilization(.)


I’m not sure what “prohibited in principle” means. Unfortunately, the article does not give a source for this story, meaning I will probably have to spend some time trying to search and translate Japanese government websites.




It seems to be this press release from the Ministry of the Environment. If Google Translate can be trusted, this PDF says:

All species of the crayfish family, America Among the species belonging to the crayfish family, the United States
Other than crayfish (Procambarus clarkii), Asian crayfish
Other than Japanese crayfish (Cambaroides japonicus) among the species belonging to
All species of crayfish, Minamizari

I’m surprised the Jiji Press story specifically mentioned Marmorkrebs, since it is not mentioned by name in the press release.


It’s been a busy week for Marmorkrebs news.


External links


About partial revision of the law enforcement regulations concerning 14 kinds such as Hayatogefu Shiari designated as a specific alien organism based on the Alien Organism Law


Raising, Selling of Nonnative Crayfish Banned in Japan (also at Nippon.com)