31 December 2010

Celebrate diversity: Cornucopia!

Parthenogensis and other unusual forms of reproduction were in the news a surprising amount this year. There were just enough other things to write about that I didn’t have a chance to write them up in detail. In some cases, though, others did that for me.

For instance, the peppermint shrimp (Lysmata wurdemanni) made New Scientist’s “coolest animals of 2010” list. Fiedler and colleagues have a more extensive review of the genus.

Boa constrictors are well-known, often kept as pets, and nobody suspected parthenogenesis in this species until this year! This was written up in lots of places (here, here, here) and the paper is still officially in press.

Finally, another parthenogenetic reptile made the news, not so much because it was parthenogenetic, but because of the way this new species was discovered. It was found as cuisine in Vietnam. This was written up here and here, and surely other places.

A more flattering picture of this interesting little beast is below.

2010 was the year of biodiversity. And I love how these stories show that there are still many more discoveries to be made, both in species we know, and species we have yet to describe scientifically.


Booth W, Johnson DH, Moore S, Schal C, Vargo EL. Evidence for viable, non-clonal but fatherless Boa constrictors. Biology Letters. http://dx.doi.org/10.1098/rsbl.2010.0793

Fiedler GC, Rhyne A, Segawa R, Aotsuka T, Schizas N. 2010. The evolution of euhermaphroditism in caridean shrimps: a molecular perspective of sexual systems and systematics. BMC Evolutionary Biology 10: 297. http://www.biomedcentral.com/1471-2148/10/297

Grismer JL, Grismer LL. 2010/ Who’s your mommy? Identifying maternal ancestors of asexual species of Leiolepis Cuvier, 1829 and the description of a new endemic species of asexual Leiolepis Cuvier, 1829 from Southern Vietnam. Zootaxa 2433: 47–61. http://www.mapress.com/zootaxa/2010/f/z02433p061f.pdf

Lysmata grabhami picture by Phillipe Guillaume on Flickr. Used under a Creative Commons license.

Boa photo from here.

29 December 2010

Hawaiian summer conference

I wanted to point out that the summer meeting of The Crustacean Society will be held in the stat of Hawaii next year, and that the call for abstracts is now available. I do so not because there are crayfish on Hawaii, but because it gives me an excuse to show this cool logo for the meeting:

28 December 2010

2010 was the best year ever for Marmorkrebs research

Last year, I couldn’t help but being a little disappointed that there had not been more papers on Marmorkrebs published than the year before.

That is not a problem this year.

And this isn’t even including a massive review chapter on crayfish that came out at the very end of the year, or a paper that got published in the last ten days of 2010, but has an official 2011 publication date on it (Jimenez & Faulkes 2011).

2010 was not only a bumper year for Marmorkrebs research, but may also have marked a turning point, as Marmorkrebs research started to go more into the field than the lab. The story of Marmorkrebs broke into news media as an emerging invasive species and pest on two fronts.

We also got several critical questions answered: What species is Marmorkrebs most closely related to? (Procambarus fallax.) Can it survive in the wild in northern Europe? (Oh, yes.)

I was also intrigued to see a surge in the number of open access papers published this year. The first had been just last year, but this year saw about half the papers published in open access journals.

With data for the first decade of Marmorkrebs research to play with, I am cautious about seeing an increasing trend. In the spirit of science, I’m going to make some predictions. According to a linear regression of the data, we should see 14 papers on Marmorkrebs in 2015, and 20 papers in 2020.

Of course, the increase might be exponential rather than linear. Too early to say, but it might be a bit exciting if it was.

And there are papers already in the wings for 2011.

21 December 2010

Jimenez and Faulkes, 2011

Jimenez SA, Faulkes Z. 2011. Can the parthenogenetic marbled crayfish Marmorkrebs compete with other crayfish species in fights? Journal of Ethology 29(1): 115-120. http://dx.doi.org/10.1007/s10164-010-0232-2


The parthenogenetic marbled crayfish, Marmorkrebs, has no known wild population, but has been introduced into natural ecosystems in two continents. Interactions with native crayfish, particularly through fighting, could affect the ecological impact of Marmorkrebs introductions. Marmorkrebs have been characterized anecdotally as having low levels of aggression, which could mitigate their potential to compete with native species. We isolated Marmorkrebs and Louisiana red swamp crayfish (Procambarus clarkii), then conducted size-matched intra- and interspecific pairings. Marmorkrebs were as likely to win a fight as P. clarkii, although contests between P. clarkii and Marmorkrebs were significantly faster to begin than contests between two Marmorkrebs. These results suggests that Marmorkrebs have the potential to compete with other species on the same level as P. clarkii, which is itself a highly successful introduced species around the world.

Keywords: aggression • crayfish • competition • invasive species • marbled crayfish • Marmorkrebs • Louisiana red swamp crayfish • Procambarus clarkii

14 December 2010

Pic of the moment: 14 December 2010

Having recently written a summary about the first 10 years of Marmorkrebs in science, I wanted to see how research on Marmorkrebs has changed, if it has.

I’ve used Wordle before on this blog, a neat little web application that makes word clouds from text. This time, I was a little more careful in cleaning it up and only using the abstract text, so it didn’t have strays like “http” or author names in there.

I divided the papers by the total number of abstracts rather than by year, because the pace of Marmorkrebs research is increasing.

The earliest abstracts (2003 to partway through 2008; 17 abstracts all told):

The most recent abstracts (late 2008 to now; 16 abstracts all told):

There is one clear change: “Marmorkrebs” has become the nom de choix for this crayfish. Interesting.

And here's the “snapshot” of the scientific literature on Marmorkrebs as it stands near the end of 2010, combining all 33 abstracts here on the blog:

07 December 2010


At least, Google Languages said that “Marmorkrebs Jungtiere” meant “Cancer marble kittens.”

01 December 2010

Faulkes, 2010

Aquatic Invasions logoFaulkes Z. 2010. The spread of the parthenogenetic marbled crayfish, Marmorkrebs (Procambarus sp.), in the North American pet trade. Aquatic Invasions 5(4): 447-450.


The parthenogenetic marbled crayfish Marmorkrebs was discovered in the pet trade in Europe in the 1990s. Since then, its distribution through the pet trade has spread from Europe to other continents, including North America. North American pet owners were surveyed online with the aims of trying to track when Marmorkrebs entered the North American pet trade, the ways in which it spread through the pet trade, and how widely distributed Marmorkrebs are throughout the continent. Marmorkrebs have been in the North American pet trade since at least 2004, with the number of people increasing every year. While many Marmorkrebs are sold through online sources, face-to-face personal contacts account for almost as many acquisitions. The increasing spread of Marmorkrebs through the pet trade increases the probability that Marmorkrebs will be released into North American ecosystems.

Key words: crustacean • aquaria • hobbyists

A Google Spreadsheet of the data shown in Figure 1 can be found here. Below is a Google Map version; the different colours represent years people first reported getting Marmorkrebs.

View Marmorkrebs pets in a larger map

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.

26 October 2010

Vogt, 2010

Vogt G. 2010. Suitability of the clonal marbled crayfish for biogerontological research: A review and perspective, with remarks on some further crustaceans. Biogerontology 11(6): 643–669. http://dx.doi.org/10.1007/s10522-010-9291-6


This article examines the suitability of the parthenogenetic marbled crayfish for research on ageing and longevity. The marbled crayfish is an emerging laboratory model for development, epigenetics and toxicology that produces up to 400 genetically identical siblings per batch. It is easily cultured, has an adult size of 4-9 cm, a generation time of 6-7 months and a life span of 2-3 years. Experimental data and biological peculiarities like isogenicity, direct development, indeterminate growth, high regeneration capacity and negligible senescence suggest that the marbled crayfish is particularly suitable to investigate the dependency of ageing and longevity from non-genetic factors such as stochastic developmental variation, allocation of metabolic resources, damage and repair, caloric restriction and social stress. It is also well applicable to examine alterations of the epigenetic code with increasing age and to identify mechanisms that keep stem cells active until old age. As a representative of the sparsely investigated crustaceans and of animals with indeterminate growth and extended brood care the marbled crayfish may even contribute to evolutionary theories of ageing and longevity. Some relatives are recommended as substitutes for investigation of topics, for which the marbled crayfish is less suitable like genetics of ageing and achievement of life spans of decades under conditions of low food and low temperature. Research on ageing in the marbled crayfish and its relatives is of practical relevance for crustacean fisheries and aquaculture and may offer starting points for the development of novel anti-ageing interventions in humans.

Keywords: marbled crayfish • Crustacea • negligible senescence • allocation of resources • epigenetics • stem cells • social stress

19 October 2010

Pic of the moment: 19 October 2010

Marmorkrebs meets cucumber.

Spotted on Twitter.

13 October 2010

Overflowing Marmorkrebs

In August, this story appeared on a German news site about crayfish escaping en masse from a pond near a school in Klepzig, Germany. On 12 October, a follow-up appeared, saying that the crayfish were Marmorkrebs.

This is bad news, if I am reading these new stories right. (I don’t read German, so I am working from a Google translation of the news story. Translation by a person would be welcomed!)

It appears that crayfish were found, in large numbers, walking out of this pond. The reasons were unknown, but overcrowding was given as a possible explanation, seen by the new story as likely given the rapid reproduction of Marmorkrebs.

Martin et al. (in press) pointed out that until now, only single Marmorkrebs have been found in Europe, never a reproducing population. This gave a glimmer of hope that Marmorkrebs might not be able to establish themselves as an invasive species in Europe. That hope glimmers a lot less brightly if the animals are walking out of water because of overcrowding, since that indicates an actively reproducing and expanding population.

Worse, both stories report astonishing sizes of the animals. The first report puts some individuals found in Klepzig at 20 cm long; the later, at 15 cm. If so, those are record-shattering sizes for Marmorkrebs. Vogt (in press) reported:

The largest specimen of my laboratory colony had reached a length of 8.8 cm... Under tropical outdoor conditions the maximum length measured was 10.7 cm (Jones et al. 2009)

50-100% larger than the largest size recorded previously is worth investigating. It suggests that the Klepzig population has been there a long time (since animals don’t grow to that size in a few weeks), and that the conditions are highly conducive to the animals.

The new article emphasizes the potential for Marmorkrebs to carry crayfish plague, which is an entirely legitimate concern. To the best of my knowledge, however, Marmorkrebs have not yet been shown to carry the pathogen. Someone needs to try infecting Marmorkrebs to see how they fare against the disease, and how contagious they are compared to other North American species.

The map of Marmorkrebs introductions has been updated to include Klepzig.


Jones JPG, Rasamy JR, Harvey A, Toon A, Oidtmann B, Randrianarison MH, Raminosoa N, Ravoahangimalala OR. 2009. The perfect invader: a parthenogenic crayfish poses a new threat to Madagascar’s freshwater biodiversity. Biological Invasions 11(6): 1475-1482.

Martin P, Shen H, Füller G, Scholtz G. 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: In press.
http://www.aquaticinvasions.net/2010/AI_2010_5_4_Martin_etal_correctedproof.pdf (Preprint)

Vogt G. Suitability of the clonal marbled crayfish for biogerontological research: A review and perspective, with remarks on some further crustaceans. Biogerontology: In press.

12 October 2010

Like a virginalis, named for the very first time

ResearchBlogging.orgThe new paper by Martin and colleagues is a significant one for the Marmorkrebs research community, because it seems to settle the problem of the species most closely related to Marmorkrebs pretty definitively. Marmorkrebs are most closely related to slough crayfish, Procambarus fallax. The picture at right compares the two; P. fallax is on top (Fig. 1 from Martin et al.)

It’s also noteworthy for being the first to tackle the thorny issue of a species name for Marmorkrebs. Martin and colleagues suggest Marmorkrebs be treated as a “form” of P. fallax, and suggest referring to Marmorkrebs as P. fallax f. virginalis. They leave open the possibility that Marmorkrebs might warrant having its own name. If that were to happen, they suggest it become Procambarus virginalis.

It’s pretty easy to guess that the word “virginalis” is derived from the same root as the word “virgin.” This is clearly a nod to Marmorkrebs’ parthenogenetic reproduction.

But “virginalis” has also been used more than once to describe a species as “white.” And one etymology used “virginalis,” somewhat prudishly, to describe a species with a “cross-legged” appearance.

Now, if I’d written the paper, I’d have suggested the scientific name be “marmoratus,” which is Latin for “marbled.” It ties into the common names for them, marbled crayfish and Marmorkrebs. And it wouldn’t risk anyone thinking that these were white crayfish.

Because “forms” are not recognized by the international committee that oversees scientific names for animals, it’s an open question at this point as to whether this naming scheme will be adapted by the community. I think continuing to use “Marmorkrebs” in addition to the name suggested by Martin and colleagues (or some variant of it) will continue to serve the research community well, for reasons I discussed here. Not only is “Marmorkrebs” distinctive, it can now provide some important continuity in the scientific literature and in search engines.

Additional: Co-author Gerhard Scholtz emailed me with this comment:

(“virginalis”) literally means “related to a virgin.” The Latin words for white are different. Only later in Christian symbolism is the white lilly a sign for the immaculate Mary (immaculate conception) and in addition for giving birth as a virgin. Immaculate conception means that Mary was born without the “original sin” (inherited from from Adam and Eve) not that she gave virgin birth, this is often confused. So the use of “virginalis” for white is very indirect. If we would have chosen “marmoratus”, and we considered this, then the characteristic
difference to P. fallax, which is also marbled, would have been given

And I fully understand the reluctance to use “marmoratus,” which is the same reason I advocate “Marmorkrebs” over “marbled crayfish.” There are an awful lot of crayfish with some sort of marbled colouration.


Martin P, Dorn NJ, Kawai T, van der Heiden C, Scholtz G. 2010. The enigmatic Marmorkrebs (marbled crayfish) is the parthenogenetic form of Procambarus fallax (Hagen, 1870) Contributions to Zoology 79(3): 107-118. http://www.ctoz.nl/ctz/vol79/nr03/art03

05 October 2010

Celebrate diversity: The fish that fertilizes itself

ResearchBlogging.orgIt’s almost another marbled clone.

There are parthenogenetic vertebrates (some of which have been featured on this blog), but the Mangrove killifish, Kryptolebias marmoratus, is the only vertebrate that regularly self-fertilizes. Most individuals have male and female reproductive organs. Obviously, this allows you to have individuals that are not quite clones, but certainly have much more limited variation than most sexual species.

But, because sex is rarely simple, some individuals in this species are just male.

And that little detail means that the hope that all these individuals will create nice, neat, clone lineages gets shot down. So Tatarenkov and colleagues decided to investigate how genetically similar these fish are to each other.

Some findings are depressingly familiar. Cell biologists have often found that what they thought was one type of cell cultures has been contaminated by nearby strains of other immortal cells. HeLa cells are particularly notorious in this regard. Similarly, Tatarenkov and company found about 20% of their marbled killifish did not have the expected genes. Incomplete record keeping meant that many sources of error, or sources of new variation they found, could not be traced back to its source.

They did find new genetic variation that appeared to have cropped up since the animals had been collected for the lab, which they attributed to new mutations. In fact, one gene seemed to be a mutational “hotspot,” mutating several times in different lines.

The major source of genetic variation, however, was the original source of the lab population. This fish has a wide distribution, and stocks collected from different locations did not resemble each other. Thus, this fish has a nice combination of being able to maintain genetic similarity within a lineage, but there remains some variation across lineages.

P.S. – If this fish’s specific name, “marmoratus,” looks a bit familiar, it’s because it is Latin for “marbled.” And that’s undoubtedly the same root for the word, “Marmorkrebs.”


Tatarenkov A, Ring B, Elder J, Bechler D, Avise J. 2010. Genetic Composition of Laboratory Stocks of the Self-Fertilizing Fish Kryptolebias marmoratus: A Valuable Resource for Experimental Research PLoS ONE 5(9): e12863. DOI: 10.1371/journal.pone.0012863

Picture from here.

28 September 2010

Martin and colleagues, 2010

Martin P, Dorn NJ, Kawai T, van der Heiden C, Scholtz G. 2010. The enigmatic Marmorkrebs (marbled crayfish) is the parthenogenetic form of Procambarus fallax (Hagen, 1870). Contributions to Zoology 79(3): 107-118. http://www.ctoz.nl/vol79/nr03/a03


A mysterious parthenogenetic cambarid crayfish (the Marmorkrebs) has been spreading across the globe for the past decade. We compare this crayfish directly to two other cambarids, Procambarus fallax and P. alleni, that have been suggested to be related or even identical to the Marmorkrebs. Using external morphology and sequences of two mitochondrial genes we show clear correspondences between Marmorkrebs and P. fallax, a species found natively throughout peninsular Florida, USA. Based on these congruent results we suggest that the Marmorkrebs is the parthenogenetic form of P. fallax. This finding has potential evolutionary and ecological implications at several levels. The Marmorkrebs might be a type of geographical parthenogenesis, but a natural population in the wild is so far unknown. Furthermore, challenges arise in regard to the respective species status of the Marmorkrebs. Taxonomically we suggest that the Marmorkrebs is treated as “form” of P. fallax. Last but not least, the identity of this animal and its ecology has an impact for considering potential spread and effects of this species across the globe.

Keywords: 12S rRNA, annulus ventralis, COI, DNA barcoding, species concept, thelytoky

Edit, 29 December 2018: Link to article updated. Really wishing more journals used DOIs...

23 September 2010

Crayfish at World Aquaculture Society conference

Tthe World Aquaculture Society meeting will be holding a special session on crayfish at the next meeting in New Orleans in March 2011. The organizing committee is still accepting abstracts for this session until 30 September 2010. The session will be chaired by Julie Delabbio and Ray McClain.

To submit an abstract, go to https://www.was.org and click on the New Orleans meeting logo.

If ever there was a place to present a paper on crayfish aquaculture, New Orleans is it.

21 September 2010

First report of Marmorkrebs in Asian ecosystems

Japan becomes the latest addition to the map of where Marmorkrebs have been found in natural ecosystems. Tadashi Kawai, the co-editor of The Biology of Freshwater Crayfish, provided me with this brief translated excerpt from the book.

The marbled crayfish was found as pet in Japanese aquarium trade. In 2006, Sapporo Salmon Museum (Sapporo City, Hokkaido) accepted the unknown crayfish from volunteer conservationists. They collected from a river from Sapporo City. As the crayfish show marble color patter on their carapace and their juvenile are all female, it identified as parthenogenetic Marmorkrebs.

The Google Map that I maintain of Marmorkrebs introductions has been updated accordingly.


Kawai T, Takahata M (eds.). 2010. Biology of Crayfish. Sapporo: Hokkaido University Press. 556 pgs. ISBN: 978-4-8329-8194-2.


Sapporo Salmon Museum picture from here.

16 September 2010


In vertebrates, nearly every case of parthenogenetic species can be traced back to a hybridization event. Does this mean it’s important to evolution generally? Jerry Coyne, whose main research is speciation, looks at this question.

13 September 2010

Could Maryland be next?

Candus Thomson, writing on the Outdoors Girl blog for the Baltimore Sun, reports that Maryland is considering adding Marmorkrebs to Maryland’s “Nuisance Species” list. I’d previously mentioned Maryland had a fact sheet about Marmorkrebs, but hadn’t realized that it was probably prepared as part of this move to consider Marmorkrebs for regulation.

The meeting happened last Wednesday, with Candus noting there were six biologists for every member of the public(!).

The public can comment on the proposed regulations by visiting here until 30 September 2010.

07 September 2010


If you read this blog, but don’t visit the home page every time, you might not have noticed another set of new papers in press that are now listed on the home page.

There are more papers in press right now than were published all of last year. Some of those might not make it to final publication (with volume and page numbers) this year, but I’m expecting most will. Which is quite an lovely surge in Marmorkrebs research.

Photo by ViaMoi on Flickr, used under a Creative Commons license.

31 August 2010

I ♥ you, Missouri and Maryland

Effective 1 March 2011, Marmorkrebs will be added to Missouri’s prohibited species list. Missouri Maryland is the first North American jurisdiction to consider Marmorkrebs specifically in their regulations, as far as I know. Marmorkrebs are already present in Missouri as pets, based on data in a forthcoming paper on Marmorkrebs in the pet trade.

Crayfish biologists generally agree that such regulations are good things. See the Lausanne Declaration by the International Association of Astacology for a summary of why.

I can’t help but be a bit chuffed that this website is listed as an information source in a Maryland fact sheet about Marmorkrebs. I’m even willing to overlook that they refer to the fake-y-not-really-a-species-name, “Procambarus marmorkrebs.” There is no such name!

So this gives me another reason to love Maryland besides that they once had a Canadian Football team. (I loved that in that year, there was a CFL team with no name, and two teams with the same name.)

Update: Corrected this post, which miscredited the legislation to Maryland, not Missouri, due to some misreading on my part. Whoops!

30 August 2010

Jirikowski and colleagues, 2010

Jirikowski G, Kreissl S, Richter S, Wolff C. 2010. Muscle development in the marbled crayfish—insights from an emerging model organism (Crustacea, Malacostraca, Decapoda). Development Genes and Evolution 220(3-4): 89-105. http://dx.doi.org/10.1007/s00427-010-0331-7


The development of the crustacean muscular system is still poorly understood. We present a structural analysis of muscle development in an emerging model organism, the marbled crayfish—a representative of the Cambaridae. The development and differentiation of muscle tissue and its relation to the mesoderm-forming cells are described using fluorescent and non-fluorescent imaging tools. We combined immunohistochemical staining for early isoforms of myosin heavy chain with phallotoxin staining of F-actin, which distinguishes early and more differentiated myocytes. We were thus able to identify single muscle precursor cells that serve as starting points for developing muscular units. Our investigations show a significant developmental advance in head appendage muscles and in the posterior end of the longitudinal trunk muscle strands compared to other forming muscle tissues. These findings are considered evolutionary relics of larval developmental features. Furthermore, we document the development of the muscular heart tissue from myogenic precursors and the formation and differentiation of visceral musculature.

Keywords: Marmorkrebs • development • muscle precursor • myogenesis • evolution

24 August 2010

Crayfish + radio = craydio?

At the recent International Association for Astacology meeting, there were some student radio reporters from KBIA about, and some of them came by to chat about the conference and listen to a little about crayfish.

You can listen here; the RSS feed with mp3 files is here.

Going back to the end of July, ResearchBlogCast discussed asexual species concepts, which started by a post on this blog about a PLoS ONE paper. A little more discussion is here. The mp3 is here.

Photo by the third dream on Flickr; used under a Creative Commons license.

23 August 2010

Hitting the wire: Orana vahiny

The German wire service Deutsche Presse-Agentur (or DPA) has released a story about the release of Marmorkrebs in Madagascar.

It started making the rounds last Wednesday. It has shown up, without modification, here:

I strongly suspect it will be showing up at other locations. I’ll be collecting links as I find them.

Meanwhile, some fact-checking:

It is not clear how or when the shrimp-like crustacean, which is believed to originate in North America, came to this vast island, which lies 400 kilometres off the coast of Mozambique.

“Shrimp-like”? Don’t most people know what crayfish look like? If you’re going to compare it to something more people will recognize, it’s more lobster-like than shrimp-like.

In 2003, German scientists proved that the marmorkrebs could clone itself. Although the crayfish also reproduced sexually, females were able to lay eggs which hatched without being fertilised.

There is no record that I know of, in the scientific literature or otherwise, indicating that Marmorkrebs ever reproduce sexually.

“We get diarrhoea after eating them,” one farmer said. “Even the pigs won’t eat them.”

There’s no reason I can think of for Marmorkrebs to be gastronomically worse than any other kind of crustacean to eat, either for humans or pigs. The quoted person may well have gotten sick after eating Marmorkrebs, but it probably had more to do with a bad batch than being generally unsuitable for eating.

I am pleased to learn that “orana vahiny” is the Malagasy name for Marmorkrebs.

17 August 2010

Celebrate diversity: Old female salamanders

ResearchBlogging.orgImagine, if you will, a line of ancient females, who trick males into having sex with them, so that the females can continue living indefinitely.

I know, you’ve seen it before in a dozens of movies, books, and television episodes. Who hasn’t seen a vain sorceress stealing youth, particularly from young men?

Something like this goes on in some salamanders, except that no one salamander is living unusually long. The evolutionary line of salamanders, though, is showing surprisingly longevity.

Some salamanders are all female... but they are not, strictly speaking, asexual or parthenogenetic. These unisexual female lineages engage in a little sperm “theft” from several sexual salamanders species (Ambystoma laterale is pictured), a process known as kleptogenesis. Genetically, these unisexual females are all over the map. Some unisexuals have a paired set of chromosomes like the more typical sexual species (i.e., they are diploid); others have three, four, or five sets of chromosomes.

This unusual mode of reproduction is interesting, because it might allow a unisexual species to avoid genetic stasis. In theory, sexual species have the edge in a changing environment because more genetic variations are possible through sexual reproduction. Having every individual be genetically identical is great as long as the environment never changes.

But environments do change, so it’s generally though that parthenogenetic species tend to go extinct at much higher rates than sexual ones.

This new paper by Bi and Bogart tries to settle how old this odd lineage of female salamanders is. One previous study suggested millions of years; another estimated tens of thousands of years. Bi and Bogart come down on the side of millions of years; a little over 5 million years, to be precise.

The reason for the discrepancy comes down to an issue concerning the wrong bit of DNA being amplified and analyzed. Most animal cells have DNA in two places: the cell nucleus (where most people think of it being), and in the mitochondria (the cell’s power plant). In normal sexual species, nuclear DNA comes equally from both parents, while mitochondrial come from mom.

Because these all-female salamanders get nuclear DNA from the sperm they “steal,” you can really only try to trace relationships using mitochondrial DNA in these animals.

The problem is that nuclear DNA sometimes has some bits in it that are extremely similar to mitochondrial DNA. These sequences, called numts, are probably derived from the mitochondria. Bi and Bogart argue that the previous research that suggested that these female salamanders split from the sexual salamanders about 25,00 years ago probably sequenced a numt instead of a mitochondrial gene.

That DNA. It’s tricky.

Parthenogenesis in Marmorkrebs is blessedly simple in comparison.


Bi, K., & Bogart, J. (2010). Time and time again: Unisexual salamanders (genus Ambystoma) are the oldest unisexual vertebrates BMC Evolutionary Biology, 10 (1) DOI: 10.1186/1471-2148-10-238

Photo by whiteoakart on Flickr, used under a Creative Commons license.

10 August 2010


Marmorkrebs and red cherry shrimp, in peaceful coexistance in someone’s tank. Exemplified by the sweet soul music in the background.

03 August 2010

Freshwater Crayfish

At the recent International Association of Astacology (IAA) meeting, there was a fair amount of discussion about one of the society’s publications, Freshwater Crayfish. Having examined a hardcopy at the meeting, I can say that they did a very nice job with the production of the last issue (pictured).

Since this is one forum that is a perfectly logical place to publish Marmorkrebs research, I’ll convey a few things I learned at the meeting.

First, Freshwater Crayfish is a journal. Because of its length time between issues, people often think that papers in it are proceedings from the IAA meeting. Nope – journal. It has an ISSN number and everything.

Second, you do not have to attend an IAA symposium, or be an IAA member to publish in Freshwater Crayfish. It is open to all. That said, the IAA could do more to facilitate outside submissions. For instance, the link to author’s instructions on the IAA website currently brings up a 2 page PDF document... that is completely blank. The author’s instructions were printed in the IAA conference booklet, so I’ll see what I can do about getting them online.

Currently, Freshwater Crayfish is indexed in Scopus, but not Thompson ISI Web of Science. There was some discussion about the future of the journal, which included a shorter time between publication, which would help it get into Web of Science. Still, “shorter delay” may be moving from every other year to every year.

27 July 2010

North American crayfish diversity threatened

ResearchBlogging.orgWhen I recently attended the International Association of Astacology meeting, it was ground into my face how bad things are for crayfish.

In Europe, crayfish are being beaten up by exotic North American species. If competition doesn’t get them, the crayfish plague that the exotics carry will.

In North America, the home to the greatest diversity of crayfish species in the world, non-indigenous species are playing a role in some regions, but habitat degradation is the bigger concern. At the Astacology meeting, we were treated to scenes like this:

Mountains are being flattened to remove coal.

Strangely, the same factors that lead to the wonderful high diversity of North American crayfish are the same factors that make them vulnerable, mainly geographic isolation. Because crayfish need to stay wet, and are not terribly mobile, they often don’t disperse very well on their own. Consequently, many species have a limited range, often falling within a few locations in a single American state.

Taylor and colleagues provide a summary of just how bad things are in North America. The take home message that every crayfish biologist and every crayfish pet owner should have burned into their brain is this:

Almost half of North American crayfish species are under threat.

I don’t use the phrase “under threat” in any sort of technical way, but just indicating some sort of conservation concern.

On a per species basis, crayfish are the second third most threatened kind of animal in North America, behind freshwater mussels and snails, which obviously have many of the same issues as crayfish: small geographic ranges, limited mobility (though crayfish are more mobile than snails and mussels), vulnerable to competition and habitat degradation.

Taylor and colleagues provide other useful information, including a list of all known species and a standard common name. The article is rather nicely illustrated with a few crayfish pictures, too (not for every species, however).

All of this makes the prospect of Marmorkrebs being introduced into North American waters a veritable nightmare scenario. Competition between Marmorkrebs and a local species could be enough to push a species into extinction.


Taylor, C., Schuster, G., Cooper, J., DiStefano, R., Eversole, A., Hamr, P., Hobbs, III, H., Robison, H., Skelton, C., & Thoma, R. (2007). A Reassessment of the Conservation Status of Crayfishes of the United States and Canada after 10+ Years of Increased Awareness Fisheries 32(8): 372-389. DOI: 10.1577/1548-8446(2007)32[372:AROTCS]2.0.CO;2

Photo by ddimick on Flickr. Used under a Creative Commons license.

24 July 2010

18th International Association of Astacology conference: Day 5

On the last day of the conference, everyone’s ready to go, having had enough of the undergrad food and residence rooms. But everyone is sad that they probably won’t be seeing some of their friends, old and new, for some time.

Impressions: Gatorade for breakfast. There is a blue crab genome project, and maybe a crayfish one. Some Engaewa burrowing crayfish look amazingly like thalassindean mud shrimp; I badly want to look at their neurons.

After the last few talks, there was a brief meeting announcing the award for best talk and best poster came out; congratulations to the four winners. The winners for the talks were David Strand in the student category and Jim Stoeckel for the professional category. (Alas, I cannot recall the poster winners. Something I ate didn't agree with me, and I was rather queasy right when they gave those awards. I didn't have the presence of mind to write down all the names.) For the record: A singing voice and Prezi is not a winning formula for a best presentation award. Congratulations to the winners.

Catherine Souty-Grosset, who had left before they tried to give her an award at last night's banquet, was present and received her award this time. They also handed over the “keys to the car” for the new president of the association, which includes a fossil crayfish. The fossil crayfish is kept by the I.A.A. president, held in a box guaranteed for life except against:

  1. Shark bites
  2. Small children

It was pointed out the incoming president Jim Fetzner (pictured above) has at least one of those.

Conference organizer Annie Allert is nicknamed “The General” for her organizational skills, but even The General succumbed at the end of the meeting, and it was touching to hear her voice when she told the delegates that they have friends in Missouri. So one last time, I salute The General and all the other organizers and delegates who made my first visit to the conference an enjoyable one.

Austria in 2012!

22 July 2010

18th International Association of Astacology conference: Day 4

The audience for talks is thinning out a bit, and so are the speakers. Two cancellations in the scheduled presentations today.

Impressions: As far as Louisiana crayfishermen are concerned, do anything you want – except pass any legislation; crayfish plague is not a fungus, but some weird phylum that I've never heard of before; porcelain disease has a pretty name but a bad effect on crayfish; IAA 19 will be in Austria for the 40th anniversary.

There are still more talks tomorrow morning, but this evening had a bit of a closing feel to it at the conference banquet. Drinks, food, music, some serious awards (career awards for Alistair Richardson and Francesca Gherhardi), and some silly awards. Delivered by a man with claws and the Crawdettes.

One award managed to combine silly and serious. Abbie came to the conference from England, and had her luggage completely lost. She's been wearing the same clothes all week. So the I.A.A. gave her a princess costume, which she is twirling in here:

Others went to the Blue Note to listen to blues. I, alas, reached the limit of how much I can do on five hours of sleep a night, so came back early.

The Flickr photostream continues to lengthen.

P.S. – My talk? The audience learned that to the tune of this:

You can sing this:

Super cloning crayfish team Marmorkrebs go!
Super cloning crayfish team Marmorkrebs go!
If you need a crayfish that's a name you should know
Super cloning crayfish team Marmorkrebs go!

And for those of you asking how I did my talk, it was made with Prezi.