30 November 2010

Chucholl and Pfeiffer, 2010

Aquatic Invasions logoChucholl C, Pfeiffer M. 2010. First evidence for an established Marmorkrebs (Decapoda, Astacida, Cambaridae) population in Southwestern Germany, in syntopic occurrence with Orconectes limosus (Rafinesque, 1817). Aquatic Invasions 5(4): 405-412.


Marmorkrebs are one of 12 currently known non-indigenous crayfish species (NICS) to be found in Central European waters. It is unique in the manner that there exist only females which reproduce parthenogenetically, i.e. eggs develop unfertilized and all offspring are genetically identical. Marmorkrebs have been first discovered in the German aquarium trade in the mid 1990s and became a very common pet species since then. Here, we present first evidence for a well established Marmorkrebs population in a small lake in the Upper Rhine catchment near Freiburg (Germany). The population occurs syntopically with Orconectes limosus, another NICS which invaded the Rhine system about 50 years ago. Morphometric and ovary weight measurements were taken from 12 Marmorkrebs specimens that were captured on July 3, 2010. The rostrum spination was pronounced and resembled the one found on a free-living individual captured in Saxony (Germany). Ovary development stages (Gonadosomatic Index) were heterogeneous and single berried females were found from early June to late July, which might indicate an asynchronous breeding habit. The relative abundance and distribution of both crayfish species were assessed by visual counts at nighttime at two occasions. Both species attained a comparable, moderate density throughout the lake margin. The Marmorkrebs was the prevalent species on shallow, swampy habitat patches, which are presumably similar to its natural prime habitats. The successful establishment of Marmorkrebs despite a pre-existing O. limosus population, stresses the competitive ability of Marmorkrebs. In addition to the recently suggested hypothesis that Marmorkrebs might be temperature limited in most parts of Europe, we feel that it is also necessary to consider its probable natural prime habitats and life cycle: Marmorkrebs are presumably able to colonize summer-warm, lentic habitats in most parts of Central Europe.

Keywords: Marmorkrebs • marbled crayfish • non-indigenous species • invasion success • parthenogenesis • Procambarus fallax

29 November 2010

Marmorkrebs in SciAm’s Guest Blog

The decade the clones came” is the title of a new post I wrote for Scientific American’s Guest Blog. I’m pretty happy with how it turned out, so please check it out.

Writing a blog like this, where I try to have something every week, has one little disadvantage: you tell the story in bits and pieces. When I was asked if I wanted to contribute to the guest blog, it occurred to me that this was a chance to pull the story of marbled crayfish together in one place. That the first mention of Marmorkrebs on the CRUST-L list was about ten years ago was also a nice coincidence, and made me think that a cohesive retrospective would be worthwhile.

I’d like to thank Bora Zivkovic for the opportunity to pull the piece. Though I say it as a contributor now, Bora has done an fantastic job of getting top notch material for the Guest Blog. If you haven’t been reading it lately, you’re missing out on some good stuff. I’m proud to be part of it!

Martin and colleagues, 2010b

Aquatic Invasions logoMartin P, Shen H, Füller G, Scholtz G. 2010. The first record of the parthenogenetic Marmorkrebs (Decapoda, Astacida, Cambaridae) in the wild in Saxony (Germany) raises the question of its actual threat to European freshwater ecosystems. Aquatic Invasions 5(4): 397–403. http://dx.doi.org/10.3391/ai.2010.5.4.09


A cambarid specimen was collected in a brook in Saxony (south-east Germany). Preliminary morphological inspection identified it as the parthenogenetic Marmorkrebs (Decapoda, Astacida, Cambaridae). However, this individual showed some striking morphological differences compared to specimens of our laboratory Marmorkrebs culture. Hence, we conducted a molecular analysis based on two mitochondrial genes, COI and 12S, to check its identity. The results of the genetic study verified the initial assumption of a Marmorkrebs identity for the Saxon specimen. Thus, in addition to the two indigenous species, the new find is the fourth recorded introduced crayfish species in this area. However, a search for further Marmorkrebs specimens at the same site was not successful. Most published records of Marmorkrebs in European waters concern just single individuals and an established population has so far not been observed. This stands in contrast to other recently introduced cambarid species. Thus, we critically discuss the potential of the Marmorkrebs to spread within Europe. The major obstacle may be that the temperature necessary for optimal development and reproduction of the Marmorkrebs is significantly higher than that found in most European waters. However, given globally increasing temperatures, this might change in the future.

Keywords: intraspecific variability • developmental noise • genetic identification • potential invader • conservation of species diversity • thermal adaption • global warming

27 November 2010

Nominate your favourite posts for Open Lab 2010

There is still time to nominate science writing for the fifth annual blogging anthology:

It can be a post that is long and technical.

Or it could be something that is short and whimsical.

Hints aside, please nominate writing from any blog that enjoy. It is a wonderful present to a writer to know a reader thought something he or she did was good.

You can nominate posts from 1 December 2009 until 30 November 2010.

23 November 2010

People keep saying that sex is good

The Why Evolution is True blog has a post by Greg Mayer on the evolution of sexual reproduction. It focuses on whiptailed lizards, which have featured on this blog before. Mayer does a nice job of laying out the apparent costs of sexual reproduction compared to parthenogenesis.


There is only one native crayfish species in Great Britain: the white-clawed crayfish (Austropotamobius pallipes). The Extinction Countdown blog is reporting that the International Union for Conservation of Nature and Natural Resources (IUCN) has made the white-clawed crayfish officially endangered.

What does this have to do with Marmorkrebs? Marmorkrebs have never been found in the wild in Great Britain, but they’ve shown up in the pet trade there at least once. More generally, nobody has shown whether Marmorkrebs can be a carrier of crayfish plague.Given that most North American species can carry it, it seems highly likely. But even if they can, that’s not a guarantee that they normally do. For all we know, Marmorkrebs in people’s aquaria in Europe may never have come into contact with crayfish plague.

More information about the conservation issues around UK crayfish can be found at Buglife (registration required).

The Buglife website says this about Marmorkrebs:

Marbled crayfish (Procambarus sp.)

This species originates from the USA, but its full identification needs to be confirmed. The Marbled crayfish is the first recorded crayfish capable of breeding when only females are present, by parthenogenesis (asexual reproduction). They are also crayfish plague carriers and voracious feeders. Although Marbled crayfish are banned from import or sale it is likely that some are being kept illegally by hobby aquarists. As it only takes one crayfish to start a population, aquarium tanks are easily over-run by them and the juveniles are very good at escaping. There is a huge risk that people may release Marbled crayfish. If this happens it won’t be long before they are found in the wild and spreading along our rivers. There are no known UK sites in the wild so far.

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

16 November 2010

A new garden for research

You’ve heard of evo-devo? Passé. The new thing is evo-devo-eco.

Cassandra Extavour has started a project for people interested in the interface of these three disciplines. It’s the Evo-Devo-Eco Network, naturally. Or, if you prefer, EDEN.

Ah, we scientists do love our acronyms.

This network would seem to be one of interest to the Marmorkrebs community, given that some of main prongs of research around the species revolve around the three prongs of evolution (“How did Marmorkrebs originate?”), development (“How much developmental variation can you have?”), and ecology (“How are these going to affect indigenous species as Marmorkrebs are introduced around the world?”).

I’ve joined the EDEN network, and you can see the lab profile here. And, if there are any undergraduates interested in this, note that while I put that I am not seeking undergraduates does not mean an automatic “No.” It’s just that I’m at a large undergraduate university, and I usually enough students from my home institution to look after. But don’t let that deter you. Let’s talk.

Hat tip to Steffen Harzsch for bringing this to my attention.

09 November 2010

Maybe some of us need a little bit of sex

Scientific American’s Guest Blog features a revolving door of bloggers and a wide range of topics. One of the most recent entries is from Thoughtomics blogger Lucas Brouwers on the fine line between sexual and asexual reproduction, a favourite topic on this blog. It’s titled, “We all need (a little bit of) sex.”

In fact, it features some species that were recently covered here, parthenogenetic salamanders. (And thanks for that link, Lucas!)

02 November 2010

The tip of the iceberg

Marmorkrebs are no longer single, lonely individuals in Europe. They’ve put down roots, so to speak, and have established populations.

The first good evidence of this came a couple of weeks ago, when news reports emerged of a population of Marmorkrebs in Klepzig, Germany. Another newspaper article on the Klepzig Marmorkrebs population has now appeared, providing more perspective on the situation, notably from Gerhard Scholz.

About a day after learning this, I learned of a new scientific paper reporting on an different established population in Germany, this time in Lake Moosweiher, near Freiburg. A preprint of the paper, by Christoph Chucholl and Michael Pfeiffer, is now available online. The Google map of Marmorkrebs introductions has been updated again to reflect the Lake Moosweiher population.

Chucholl and Pfeiffer suggest that their population could be merely the tip of the iceberg. The Klepzig story makes it seem very likely that they are right.