28 December 2012

The parthenogenesis slideshow

The Science Now blog, part of Science magazine, has a nice slideshow of animals that undergo parthenogenesis. Marmorkrebs appear as entry number five out of eight. The caption reads:

The parthenogenetic form of the North American crayfish Procambarus fallax, marmorkrebs are a popular aquarium pet. Their capacity for virgin birth was first discovered in Germany in 2003, when aquarium owners noticed that crayfish housed alone were laying eggs that developed into healthy adults. Genetic analysis and laboratory experiments confirmed that the animals were reproducing through parthenogenesis. Ecologists worry that their accidental release into the wild could seriously harm native crayfish, because a single individual can start a self-sustaining population, leading some states to prohibit their ownership.

“Some states” is currently a bit of an overestimate, since that number is, as far as I know, one.

Check out the other seven entries here.

11 December 2012

Chucholl, 2013

Chucholl C. 2013. Invaders for sale: trade and determinants of introduction of ornamental freshwater crayfish. Biological Invasions 15(1): 125-141. http://dx.doi.org/10.1007/s10530-012-0273-2


The trade of live ornamental freshwater crayfish has grown rapidly in the last decade and has become the major pathway for new non-indigenous crayfish species (NICS) introductions into Europe. Here, I report on the German ornamental crayfish trade, the main importer of non-indigenous crayfish into Europe. In total, 120 NICS have been available as ornamental aquarium species. One hundred and five species originate from North or Central America and are, therefore, suspected to be crayfish plague vectors. The import rate since 2005 was estimated to be seven new species per year. Despite many species being imported, only eleven species were found to be very common in the trade. In 2009, 16 online shops offered at least 37 NICS. The availability, price, and size of the offered species were used to predict their introduction status. Multiple binary logistic regression analysis showed that species’ availability and size were the principal predictors of the likelihood of being recorded as introduced from aquaria. NICS introduced from aquaria were found to be more available and larger than those present only in aquaria, and their potential invasiveness was also higher. The findings are consistent with the propagule pressure hypothesis in that a greater availability is likely related to more release events, and large species may be released more frequently as a result of overpopulating or outgrowing their aquaria. Efforts to mitigate the risk of further harmful crayfish introductions from aquaria should aim to drastically reduce the availability of high-risk species.

Keywords: live animal trade • introduction pathway • alien crayfish • aquarium discards

I’d read that

04 December 2012

Oddly soothing

20 November 2012

#SciFund recovery

“Dream come true” sounds too hokey. “I love it when a plan comes together” sounds too smug.

It was a long week of hard work, much of it hard physical labour, with a lot of mistakes and frustrations. By the end of it, I felt like this:

Ready for it to be over.

But I achieved everything I set out to achieve... in miniature. This is in line with the spirit of #SciFund, since #SciFund was a miniature grant.

I set out for crayfish, and I got crayfish:

I got small animals, little tiny hatchlings. These are going to have to grow for a while before they’re any good to me.

I set out for sand crabs, and I got sand crabs:

I got a small number of animals, less than the number of my fingers. I have enough for to be useful for at least one project.

All the way through the trip I was very aware that this was possible because of the generosity of people who donated to #SciFund. I was frequently updating a blog I created for supporters, and journaling the expedition for an audience made the trip a little less isolating.

Would I have liked to have had a few more data points, the important thing was that I did not come away empty handed. It was wonderful to be out in the field, trying to tackle problems and do things that I had been thinking about for a couple of years. Now I will have to spend a few more months thinking and working before I know what to do next.

(Crossposted from NeuroDojo.)

12 November 2012

#SciFund update

I swear to you, this is purely coincidence.

It is purely coincidence that today:

  • I am getting on a plane to Florida on a crustacean collecting trip powered by #SciFund support, and...
  • Round three of #SciFund launches!

It’s been a long time coming for my #SciFund expedition. Round 1 was about this time last year. Then, I was so focused on doing the project that I didn’t realize that the slough crayfish I wanted to collect were seasonal, and the best time to collect them was November.

I will be blogging about my #SciFund trip here, but only a little bit. My supporters from round 1 and 2 will be getting access to s special expedition blog, Amazons and Goliaths, where I will be blogging much more extensively and in a much different format than here.

I should also say that Kyle McLea, who had a Marmorkrebs project in Round 2 of #SciFund, recently got a whole lot of crayfish shipped to him. So his crowdfunded research is on a roll now, too.

As for round three of #SciFund, this is the first time I do not have a horse in this race, so to speak. But you should go to Rockethub and check out all the cool projects!

08 November 2012

Chucholl and colleagues, 2012

Chucholl C, Morawetz K, Groß H. 2012. The clones are coming – strong increase in Marmorkrebs [Procambarus fallax (Hagen, 1870) f. virginalis] records from Europe. Aquatic Invasions 7(4): 511-519. http://dx.doi.org/10.3391/ai.2012.7.4.008


We describe a new occurrence of parthenogenetic Marmorkrebs in southwestern Germany and give a synopsis of recent records of this species in Europe. Including the most recent records, 15 Marmorkrebs records are currently known, most of which are from Germany. At least six records represent established populations, which is an alarming increase beyond the one Marmorkrebs population known prior to 2010. Most established populations occur in lentic habitats near conurbations, typically in highly frequented secondary habitats, such as gravel pit lakes. In three instances, Marmorkrebs migrated over land, demonstrating their potential for active spread, and two invasive populations endanger indigenous crayfish populations. Most Marmorkrebs populations are large and are most likely several years old, suggesting a considerable lag between introduction and detection. Marmorkrebs populations in Europe are most likely the result of deliberate releases from aquaria, although secondary introductions may have occurred in one instance. Because Marmorkrebs are still widespread in the European pet trade, which most likely generates substantial propagule pressure, it is likely that the number of established populations will further increase over time. To mitigate the risk of further harmful crayfish releases, we suggest the prohibition of trading live high-risk crayfish species, including Marmorkrebs.

Keywords: aquarium introductions • marbled crayfish • invasiveness

06 November 2012

Marmorkrebs on the road: SICB 2013

The new newsletter of The Crustacean Society has this to say about the Society for INtegrative and Comparative Biology meeting in January:

TCS winter meeting / Society of Integrative and Comparative Biology (SICB)
January 3-7, 2013, San Francisco

SICB logoThe Crustacean Society winter meeting is held in conjunction with the Society of Integrative and Comparative Biology (SICB) and this year the meeting will take place from January 3-7, 2013 at the Hilton near Union Square in downtown San Francisco. Tadashi Kawai (co-editor of Biology of Freshwater Crayfish) will chair a special session on the Biology of Crayfish which features talks by Gerhard Scholtz, Zen Faulkes, Keith Crandall, Peer Martin, Christoph Chuchold, Antonio Garza de Yta, Teresa Feria, and Francesca Gherardi. The Special Session will take place on Monday January 7th from 8:00-12:00. The Special Session is being sponsored in part by TCS. Additionally there will be over 40 other talks and posters related to Crustacea. There are 12 diverse symposia and I would like to draw your attention to one symposium co-organized by Todd Oakley from the University of California Santa Barbara (Integrating Genomics with Comparative Vision Research of the Invertebrates) as there are multiple crustacean talks included. On a more social note, TCS in conjunction with the Division of Invertebrate Zoology and American Microscopical Society will host a social on Sunday January 6th in the evening from 6:15 until 9:15. The TCS business meeting will be concurrent with the social from 6:15-7:15. Last year it worked out well to grab a bit of food, attend the business meeting and then rejoin non TCS colleagues at the social. There will be the Libbie Hyman auction hosted by Division of Invertebrate Zoology also in conjunction with our social. Be prepared to bid on some exciting invertebrate treasures. We are very fortunate that Burke and Associates negotiated very reasonable room rates for San Francisco ($129/night) which is quite inexpensive for this city. There are plenty of reasons to attend this meeting in addition to the great science. Extend your visit to San Francisco and walk over the Golden Gate Bridge, visit China town, spend a day at the De Young Museum in Golden Gate Park or browse the shelves at the City Lights Book Store in North Beach. Please plan on attending this year’s winter meeting and dropping by the TCS booth to say hello. If you have any questions please feel free to contact me (sltamone@uas.alaska.edu).

Sherry Tamone
SICB Liaison Officer

09 October 2012

More Marmorkrebs meetings in San Francisco

There will be a special session on Marmorkrebs at the next Society for Integrative and Comparative Biology meeting in San Francisco. It's not exactly a full blown regular symposium, so you won’t see it in the schedule yet. But it will be happening, and I will post more details as I learn them.

You can find more details about the meeting here.

Early registration for the meeting  closes 3 December. You can still register after that, but then prices go up.

13 September 2012

Finish that crayfish paper!

Jim Fetzner, the managing editor for the journal Freshwater Crayfish, recently sent an email indicating that they are hoping to publish the next volume, number 19, in December.

The deadline for submissions for the next volume is 1 October 2012.

As noted before, the International Association of Astacology is making efforts to get this journal published more frequently. I applaud this, as having the journal on such irregular schedule that people don’t know whether it’s a journal, or conference proceedings, or something else, does nobody much good. But the journal will only improve if they get submissions.

11 September 2012

As in the cage, so in the wild

Brian Switek (a.k.a. Laelaps) reports on a new case of parthenogenesis in the wild, in not one, but two species of snakes this time: copperheads and cottonmouths.

(I)n zoos and aquariums, zoologists have begun to document the strange phenomenon of facultative parthenogenesis: females of species that usually reproduce sexually, delivering offspring without mating. Surprise pregnancies have been documented among birds, sharks, snakes and Komodo dragons (Varanus komodoensis), but until now, only in captivity.

Very interesting stuff. Clearly some implications for the various reports of parthenogenesis in crayfish...

16 August 2012

Human parthenogenesis?

I had no idea that in 1956, there was a claim of human parthenogenesis that was taken quite seriously. There was an article in The Lancet and everything.

The Telegraph has the story by , “The modern-day virgin birth.” To this day, it is not clear how the girl, Monica Jones, was conceived, though Prasad has some speculations.

Hat tip to Jennifer Oullette.

10 July 2012

Where are the Procambarus clarkii clones?

ResearchBlogging.orgSome years back, a paper came out purporting to have identified genetically identical red swamp crayfish (Procambarus clarkii) in China (Yue et al. 2008). At the time, this was a rather remarkable claim, given that there have been no shortage of labs looking at this species. You would have expected that if P. clarkii could reproduce by parthenogenesis, someone would have noticed by now.

The plausibility of that claim went up, in my mind, with the discovery of facultative parthenogensis in spinycheek crayfish (Orconectes limosus). If Marmorkrebs and spinycheek crayfish, two species in different genera, could be parthengenetic, it seemed plausible that there was more reproductive flexibility than we thought in crayfish. And we’ve been caught off guard with other well studied species being facultative parthenogens.

The likelihood of P. clarkii clones has, in my mind, gone back down again with the publication of a new paper by Li and colleagues. In a study looking at the genes of P. clarkii across China, they found no evidence of genetically identical organisms. In fact, they say the exact opposite:

All the P. clarkii populations in China showed relatively high genetic diversity(.)

Procambarus clarkiiIn some ways, the papers are broadly comparable in their methods: both are using cytochrome oxidase (COI) genes and microsattelites. But it is fair to say that the new paper may not have found clones because that wasn’t what they had set up their experiment to find. This paper is very much interested in the red swamp crayfish as an invasive species, which meant sampling across a wide geographic range. The previous paper by Yue et al. (2008) sampled more individuals at fewer collection sites. Intensive sampling at a small number of locations would be much more likely to detect genetically identical individuals.

The claim of parthenogenetic P. clarkii still needs confirmation. The best way would be to have an identified, isolated parent in the lab and DNA genotyping of both parent and offspring.

And I’m still waiting for confirmation of whether there are Marmorkrebs in China!


Li Y, Guo X, Cao X, Deng W, Luo W, Wang W. 2012. Population genetic structure and post-establishment dispersal patterns of the red swamp crayfish Procambarus clarkii in China. PLoS ONE 7(7): e40652. 10.1371/journal.pone.0040652

Yue GH, Wang GL, Zhu BQ, Wang CM, Zhu ZY, Lo LC. 2008. Discovery of four natural clones in a crayfish species Procambarus clarkii. International Journal of Biological Sciences 4(5):279-282. http://www.biolsci.org/v04p0279.htm

27 June 2012

Faulkes and colleagues, 2012

Faulkes Z, Feria TP, Muñoz J. 2012. Do Marmorkrebs, Procambarus fallax f. virginalis, threaten freshwater Japanese ecosystems? Aquatic Biosystems 8: 13. http://dx.doi.org/10.1186/2046-9063-8-13



One marbled crayfish, Marmorkrebs, Procambarus fallax f. virginalis (Hagen, 1870), was discovered in a natural ecosystem in Japan in 2006. Because Marmorkrebs are parthenogenetic, they could establish a population from only a single individual, and thus pose a risk for becoming established in Japan, as they have in other countries. There are two major reasons to be concerned about the possibility of Marmorkrebs establishing viable populations in Japan. First, Japan’s only endemic crayfish, Cambaroides japonicus (De Haan, 1841), lives throughout Hokkaido and is endangered. Introduced Marmorkrebs are potential competitors that could further threaten C. japonicus. Second, Marmorkrebs live in rice paddies in Madagascar and consume rice. Marmorkrebs populations could reduce rice yields in Japan.


We created five models in MaxEnt of the potential distribution of Marmorkrebs in Japan. All models showed eastern Honshu, Shikoku and Kyushu contain suitable habitats for Marmorkrebs. Hokkaido, the main habitat for C. japonicus, contained much less suitable habitat in most models, but is where the only Marmorkrebs in Japan to date was found.


Marmorkrebs appear to be capable of establishing populations in Japan if introduced. They appear to pose minimal threat to C. japonicus, but may negatively affect rice production.

Keywords: None provided.

05 June 2012

Mięsikowski and colleagues, 2012

Mięsikowski M, Napiórkowska T, Templin J, Wilczyńska B. 2012. Embryonic development of Marmokrebs (Procambarus fallax forma virginalis, Hagen 1870). Acta Biologica Cracoviensia Series Botanica 54(suppl. 1): 69. http://www.ib.uj.edu.pl/abc/pdf/suppl54_1/sup_54_s1.pdf#page=33 (Conference abstract only)


Marmokrebs (sic) are very interesting objects of study because of the possibility of parthenogenetic development. Attention was paid to him in the 90s the last century when a German pet shops came as breeding animal. Currently, the wild population of this crayfish exist in Eastern Europe, North America, Madagascar and Japan (Jones et al., 2008; Faulkes, 2010). This species due to the specific way of reproduction, high fecundity, small food selectivity and ease of adaptation to different environmental conditions is treated as a potentially invasive species. It is believed that it could threaten like native populations of aquatic invertebrates and fish (Scholtz et al., 2003).

Research on development of marmokreb (sic) were conducted in laboratory conditions in an aquarium with a capacity of 90 liters. In each breeding aquarium was placed on three females. After laid eggs the females were transferred to a separate tank. Water temperature which kept incubation female was about 22°C and pH 7.90–8.15. In order to observe the successive stages of development were taken from the incubating female three eggs every 12 hours. It was made biometric measurements of embryos and photographed the next stages of development.

It was found that the breeding conditions Procambarus fallax development take about 30 days. Eggs have spherical shape with diameter of 1.5 mm. Identified 10 embryonic stages, which coincide with the observations of Alweys (sic) & Scholtz (2006).

Keywords: None provided.

Note: Contrary to the above, there are no known wild populations of Marmorkrebs in North American or Japan.

31 May 2012

Vogt, 2012b

Vogt G. 2012. Hidden treasures in stem cells of indeterminately growing bilaterian invertebrates. Stem Cell Reviews and Reports 8(2): 305-317. http://dx.doi.org/10.1007/s12015-011-9303-1


Indeterminate growth, the life-long growth without fixed limits, is typical of some evolutionarily very successful aquatic invertebrate groups such as the decapod crustaceans, bivalve molluscs and echinoderms. These animals enlarge their organs also in the adult life period and can regenerate lost appendages and organs, which is in sharp contrast to mammals and most insects. Interestingly, decapods, bivalves and echinoderms develop only rarely neoplastic and age-related diseases, although some species reach ages exceeding 100 years. Their stem cell systems must have co-evolved with these successful life histories suggesting possession of unknown and beneficial features that might open up new vistas in stem cell biology. Research of the last decade has identified several adult stem cell systems in these groups and also some mature cell types that are capable to dedifferentiate into multipotent progenitor cells. Investigation of stem and progenitor cells in indeterminately growing bilaterian invertebrates is assumed beneficial for basic stem cell biology, aquaculture, biotechnology and perhaps medicine. The biggest treasure that could be recovered in these animal taxa concerns maintenance of stem cell niches and fidelity of stem cell division for decades without undesirable side effects such as tumour formation. Uncovering of the underlying molecular and regulatory mechanisms might evoke new ideas for the development of anti-ageing and anti-cancer interventions in humans.

Keywords: adult stem cells • stem cell niche • Decapoda • Bivalvia • Echinodermata • indeterminate growth • regulation • regeneration • cancer • ageing

The $100,000 challenge

The current round of #SciFund ends today.

Kyle McLea’s Marmorkrebs project made it total long ago. Indeed, it’s been this round’s “break-out project” in terms of percent raised compared to target - more than 200%.

But I want to talk a bit about the overall amount we’ve raised at #SciFund. We cracked the $90,000 mark yesterday.

I cannot tell you how fantastic it would be to hit the $100,000 mark. So please, check out the projects to see if there are any that would like to support, even with a dollar or two. (Moral support matters a lot!)


There is nothing preventing you from giving a little extra to a project that has hit 100%. If you cannot donate, please spread the word that time is running out to be part of something great.

29 May 2012

Never send a sibling to do a clone’s job: Part 2

More guest post goodness from Kyle McLea! Check Part 1 here.

Crayfish are quite tractable for neuro experiments, including nervous system organization and function, and have been useful in many past experiments.

Importantly, as a crustacean biologist, I can also see how they’d be useful models for other, larger, more “economically important” decapod crustaceans like lobsters and crabs, for which rearing is very difficult or impossible with current techniques. Although Marmorkrebs have a fairly long generation time and only a “primitive” crustacean has had its genome sequenced, marbled crayfish are easily kept and reared and have a number of other reasons in their favor as a useful model organism.

Now, I don’t want to tread where others have already walked. Important in the “What can we use the Marmorkrebs to study?” literature is Günter Vogt’s 2008 article in the Journal of Zoology.

Vogt discusses many reasons why Marmorkrebs are of use to a scientist—they are easily grown and cared for, they “breed” all year round, all life stages are accessible for examination, and more. They have large eggs found outside the body that are excellent for those studying development from the embryonic stage to adulthood.

He goes on to make the case that marbled crayfish will be useful for developmental biology, stem cell research, and studies of regeneration. In addition, because the animals are genetically identical, epigenetics and epigenomics may be a powerful niche where these clone crayfish can prove their utility. Epigenetics is the study of variation that is not dependent on the DNA sequence of an organism—and in epigenetics we see marks of diet, aging, and other happenstances of life stamped “upon” the DNA but not actually changing its sequence. The definition of an epigenetic effect is seeing differences in some phenotype (outward appearance of a trait) in an organism among isogenic (genetically-identical) animals. For epigenetics, which will be enormous in 21st century biology, a genetically identical crayfish may be just what we need.

Vogt also goes on to recommend marbled crayfish for studies of evolution and for toxicology studies. I’m going to talk about the latter before moving on to some other reasons to be excited about these incredible crayfish.

Crayfish have long been lauded as “sentinel species” for monitoring environmental quality. A number of parameters of crayfish physiology are helpful to scientists studying pollution, including how these animals survive, what metals or contaminants they accumulate in their tissues, and more. So, Marmorkrebs can certainly serve just as well as other crayfish. But in fact, their genetic identity is of further use in toxicology studies. Smaller numbers of animals in a given strain are needed for testing if they are all genetically identical and react similarly to a drug or toxin. And although it seems counter-intuitive, testing a few different strains or lines within a species may demonstrate greater total genetic variance than looking at a single outbred strain of animals in greater numbers. So in the end, we can maintain large numbers of the small marbled crayfish for toxicology studies, minutely manipulate their environment by introducing drugs or environmental chemicals, and perhaps get a better read out on toxicities and safety than we might even get from rodents. Now, I think a lot more studies are really needed before we could actually demonstrate that, but it is a potential use. And these animals would surely be better models for toxicology of invertebrates regardless.

Finally, I also think these clone crayfish will make a great model organism for genetic studies. We don’t have many macroscopic (visible without microscopy), multicellular organisms that are both isogenic and easily genetically manipulable. (That is, can we introduce new genes? Can we change the ones that are there?) Marmorkrebs could fill that need.

Now, we have a long way to go, since cell culture is currently problematic for crustaceans, we have had only limited success manipulating gene expression in crustaceans, and less success has been had in developing transgenic decapod crustaceans. But once some of these problems have been addressed, I think the scientific community may be more willing to accept Marmorkrebs as a useful genetic tool in the study of invertebrate genetics.

Which brings me to the ultimate point of this entire article, for those who are still reading. I have a project that is a small step in the study of marbled crayfish and their genetics.

In collaboration with Doctor Zen, I’m raising money (through the #SciFund Challenge) to study the genes of Marmorkrebs and get a lot more information about their organization and the similarity between lines descended from different crayfish mothers. How genetically identical are they? What differences do we see between lines? How about if we compare them with the sexual version of Marmorkrebs, Procambarus fallax? (Which I haven’t mentioned, but is another whole neat aspect of the Marmorkrebs story!) There is so much to learn.

See the video here. (It’s better than Cats. Okay, not really.)

But if you’ve read this far and are interested to help us learn more, consider funding this project with a $1 or $5 donation here. Or if you can’t donate, consider spreading the word to your friends and social networks.

Thanks, and remember: Never send a sibling (or some outbred critter) to do a clone’s job. That’s what we have Marmorkrebs for.

Kyle, scientist at Colorado State University and science blogger at By Way of Science.

25 May 2012

BioInvasions Records

Several Marmorkrebs papers have been published in Aquatic Invasions. Some of the people involved in that journal have created a new journal.

We wish to announce the release of the very first edition of BioInvasions Records.

BioInvasions Records is an open access, peer-reviewed international journal focusing on applied research on alien species and biological invasions in aquatic and terrestrial ecosystems of Europe, North America and other regions. The journal provides the opportunity of timely publication of first records of aquatic and terrestrial invaders and other relevant information needed for risk assessments and early warning systems. Also, relevant technical reports and conference proceedings can be considered for publication in this journal.

We welcome submissions to the journal and of course encourage you to use it as a resource.

To be honest, I hope this journal never gets a Marmorkrebs paper, because that would mean another introduction of Marmorkrebs. Indeed, this is one journal that I wish would fail... but only because there were no biological invasions to report.

23 May 2012

Hippler and colleagues, 2012

Hippler D, Hu N, Steiner M, Scholtz G, Franz G. 2012. Experimental mineralization of crustacean eggs: new implications for the fossilization of Precambrian–Cambrian embryos. Biogeosciences 9: 1765-1775. http://dx.doi.org/10.5194/bg-9-1765-2012


Phosphatized globular microfossils from the Ediacaran and lower Cambrian of South China represent an impressive record of early animal evolution and development. However, their phylogenetic affinity is strongly debated. Understanding key processes and conditions that cause exceptional egg and embryo preservation and fossilization are crucial for a reliable interpretation of their phylogenetic position. We conducted phosphatization experiments on eggs of the marbled crayfish Procambarus that indicate a close link between early mineralization and rapid anaerobic decay of the endochorional envelope. Our experiments replicated the different preservational stages of degradation observed in the fossil record. Stabilization of the spherical morphology was achieved by pre-heating of the eggs. Complete surface mineralization occurred under reduced conditions within one to two weeks, with fine-grained brushite (CaHPO4·2H2O) and calcite. The mechanisms of decay, preservation of surface structures, and mineral replacement in the experiment were likely similar during fossilization of Cambrian embryos.

Keywords: None provided.

Note: This is the final version of record of a paper that previously appeared as a discussion paper; abstract here.

22 May 2012

Never send a sibling to do a clone’s job: Part 1

Today, a guest post from Kyle McLea, who has been carrying the Marmorkrebs banner for this round of #SciFund.

As a crustacean biologist who has chiefly studied crabs and lobsters, I’ve been fascinated by the marbled crayfish (Marmorkrebs) for years and for a number of reasons that I’ll detail below. But the first thing that attracted me was simply this.

Really? A crayfish that clones itself?

When Doctor Zen asked me to guest blog on the Marmorkrebs blog I was sure I had a lot to say about my interest in these fascinating critters, but I also wanted to speak to the wider interest of the scientific community. In short: Why should scientists (and the public) care?

To which I say: Never send a (mere) sibling to do a clone’s job.

Let me explain.

Marmorkrebs are a parthenogenetic crayfish. All known examples are female and reproduce themselves entirely without sex. This makes it the first example of a decapod crustacean (and there ~15,000 known species of crabs, lobsters, shrimp, and crayfish!) that only reproduces asexually. There have been a couple of other examples of crayfish that have been found to be genetically identical or to sometimes reproduce asexually, but marbled crayfish were the first found to procreate this way exclusively.

So, in a word, we’re dealing with clone crayfish.

To anyone who’s been following the molecular biology revolution over the past 30ish years, the word clone has both amazing power and amazing misuse and confusion. Clone can mean a lot of things. In this case, I’m not talking about cloning genes (experimentally extracting pieces of nucleic acid, sequencing them, and using them to assemble recombinant—new—combinations of DNA sequence for introduction to a different organism) or about using somatic-cell nuclear transfer to clone embryos (like Dolly the sheep). What I’m saying is that mother and daughter marbled crayfish should be genetically identical, or nearly so, much like identical twins in humans.

It turns out that scientists have thought a lot about the benefits of studying genetically identical individuals in a population, pretty much for as long as there has been a science of genetics. Case in point for inbred (nearly genetically identical) organisms:

“Just as the purity of the chemical assures the pharmacist of the proper filling of the doctor’s prescription, so the purity of the mouse stock can assure a research scientist of a true and sure experiment...In experimental medicine today... the use of in-bred genetic material... is just as necessary as the use of aseptic and anti-septic precautions in surgery.” —C.C. Little, 1936

Now Little may have held some ill-conceived notions about eugenics and the role of tobacco in causing cancer, but on the importance of genetically-identical (isogenic) and inbred laboratory strains he was a pioneer. His work to build up the Jackson Laboratory in Bar Harbor, Maine (the mecca of 5000 unique strains of mice), was a key part of the rise of defined strains and breeds of laboratory animals that continues today.

Those laboratory strains serve as “models” for various human diseases and for particular functions of human physiology, such as immunity or heart function. Among the model organisms listed at NIH, for instance, everything from yeast to mouse and Daphnia to zebrafish can help us to learn about different aspects of human biology and beyond.

But in each case the normal biological variation within an organism confounds us and complicates our study. Unless we want to see the full extent of biological variance (and sometimes we do—safety and efficacy testing of drugs on different populations, anyone?), having organisms that are as close to identical as possible is (often) the goal.

For mice and rats, you might have to backcross (do parent/offspring matings) for more than 20 generations to have a sufficiently inbred line to call it “genetically identical” (and I suspect some gene variation may still exist). Now, mice breed fast, but 20 generations is still real time (years) in the life of a scientist. In the mean time, scientists resort to use of siblings, littermates, or much less inbred animals. These animals have many more differences at the genetic level.

I know you’re seeing where I’m going with this… if an organism started out genetically identical, you’d have a great edge in using this organism to study any number of interesting things. Bringing us back to Marmorkrebs.

Lines of the marbled crayfish are believed to be genetically identical because they do not participate in the normal exchange and shuffling process that accompanies sexual reproduction. But of course, mutations happen to us all. So they’re not likely to be absolutely 100% identical between individuals, but much closer than anything else in the world except for natural identical twins/triplets/etc.

So, I say, send in the clone crayfish. With these animals, we don’t need to compare results with a genetically-different sibling or with an unrelated animal. This unique animal can not only be a useful biological model, but we also don’t have any easily-reared decapod crustacean that can really compete with marbled crayfish, if you take into account their genetic identity.

While they might not be a great model organism for general human physiology (they are crustaceans, after all), there are some specific ways they can help us understand human physiology (e.g., nerves) and they have a lot of other potential uses as a model organism.

Kyle, scientist at Colorado State University and science blogger at By Way of Science. Come back next week for Part 2!

15 May 2012

How many names do you need?

The question of what to call Marmorkrebs in the scientific literature has bubbled up again. When I started the blog, there was no proper scientific name, and I suggested using the name “Marmorkrebs,” because it was distinctive. I thought the matter was relatively settled, scientifically speaking, when Martin and colleagues proposed Procambarus fallax f. virginalis as a scientific name for Marmorkrebs.

A paper by Johnson and colleagues poses a strange puzzle. For some unknown reason, they coin an entirely new name for Marmorkrebs: Procambarus sp. malgasy. Nobody else has used this terminology, although Jones and colleagues do refer to “Malagasy Procambarus” in their paper on Marmorkrebs in Madagascar. Maybe it was meant to be Procambarus sp. Malgasy, with the “Malgasy” purely as an descriptive adjective. Then someone at the editing or proofing stage changed the formatting to resemble a species name.

Even so, it doesn’t explain why they wouldn’t refer to Marmorkrebs as “P. fallax f. virginalis.” They have clearly read the paper by Martin and colleagues – it’s in the list of references.Plus, the analysis by Johnson and colleagues supports that Marmorkrebs is most closely related to P. fallax.


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. http://dx.doi.org/10.1007/s10530-008-9334-y

Johnson GT, Elder JF, Jr., Thompson SM, Hightower P, Bechler D. 2011. Phylogeny of the freshwater crayfish subfamily Cambarinae based on 16S rDNA gene analysis. Current Trends in Ecology 2: 97-113. http://www.researchtrends.net/tia/abstract.asp?in=0&vn=2&tid=66&aid=3396

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://dpc.uba.uva.nl/ctz/vol79/nr03/art03

12 May 2012

SciFunded... again!

A big congratulations to Kyle McLea, whose #SciFund Marmorkrebs research project, Crayfish Clone Wars, is now funded.

More impressive, Kyle not only hit his target early, he kicked it a few times and knocked it over for good measure.

Just because a project has met its target, however, does not mean that you can’t still give a donation. You can continue to fuel #SciFund projects until the end of May!

For more crustacean goodness you can support on #SciFund, consider:

A Climate for Castrators? by Alyssa Gehman, which is about the mud crab, Eurypanopeus depressus, and its parasite, Loxothylacus panopeus.

Beach of the Goliath Crabs by Zen Faulkes (me!), which is about the sand crab, Lepidopa benedicti.

08 May 2012

Johnson and colleagues, 2011

Johnson GT, Elder JF, Jr., Thompson SM, Hightower P, Bechler D. 2011. Phylogeny of the freshwater crayfish subfamily Cambarinae based on 16S rDNA gene analysis. Current Trends in Ecology 2: 97-113. http://www.researchtrends.net/tia/abstract.asp?in=0&vn=2&tid=66&aid=3396


Freshwater crayfish have been a mainstay in biological experiments as a model species ever since Huxley’s seminal publication The Crayfish. Crayfish have been used in research ranging from vision pigment studies to neural physiology. Non-native species have been introduced on four continents due to their immense economic value. Although crayfish taxonomy is reasonably well resolved at the highest levels, there are many problems at the levels of genus and species. New exploration, technology and methodology have led to the discovery of not only new species but to a phylogenetic complexity that would not have been imagined in Huxley’s era. This complexity is caused by the conservatism of some morphological characters, high intraspecific diversity and convergence. The ambiguity of crayfish taxonomy is particularly evident for species native to South Georgia and North Florida, which are centers of crayfish diversity. Molecular phylogenetic analyses were employed to provide insight into three aspects of crayfish phylogeny. Using partial data from the 16S ribosomal gene, we determined: (a) the evolutionary relationships of a previously unanalyzed species, Procambarus spiculifer, (b) relationships within the genus Procambarus, and (c) the phylogeny of the entire subfamily Cambarinae. The resulting maximum likelihood tree produced phylogenies that were significantly different from the traditional systematic representation of relationships within the subfamily. Specifically, we show that the subfamily Cambarinae should not be divided into three distinct clades according to the genera Procambarus, Cambarus, and Orconectes. While most members of the genus Procambarus cluster within a single monophyletic clade, the genus Orconectes comprises a parayphyletic grouping that appears to also include members of the genus Cambarus.

Keywords: Procambarus spiculifer • Cambaridae • 16s rDNA • astacidae • paratacidae • phylogenetics

Note: Marmorkrebs is referred to in this paper as “Procambarus sp. malgasy.”

01 May 2012

SciFund 2 begins!

SciFund is back! Hosted once again by the fine folks at RocketHub, there are a whole mess of scientific research projects for you to support!

Look for Kyle McLea’s Marmorkrebs project, Crayfish Clone Wars!

You should go to RocketHub now and support scientific research!

25 April 2012

Martin and Scholtz, 2012

Martin P, Scholtz G. 2012. A case of intersexuality in the parthenogenetic Marmorkrebs (Decapoda: Astacida: Cambaridae). Journal of Crustacean Biology 32(3): 345-350. http://dx.doi.org/10.1163/193724012X629031


We describe an intersex specimen of the Marmorkrebs, the only obligate parthenogenetic freshwater crayfish with an all-female population. The individual was a fully functional female which possessed male-like first pleopods. Nevertheless, it reproduced successfully and the offspring were normally developed parthenogenetic females, lacking any trace of male traits. The general rarity of aberrant sexual traits in freshwater crayfishes, in particular in Procambarus, is discussed. We suggest that a dysfunction of the sex determining system, which controls the anlagen of the androgenic glands during development, caused the partial male-like phenotype of this Marmorkrebs specimen. The application of this organism for investigations of sex determination and differentiation is recommended.

Keywords: aberrant secondary sexual characteristics • androgenic gland • gonochorism • gynandromorphy • hermaphroditism

23 April 2012

Soedarini and colleagues, 2012

Soedarini B, Klaver L, Roessink I, Widianarko B, van Straalen NM, van Gestel CAM. 2012. Copper kinetics and internal distribution in the marbled crayfish (Procambarus sp.). Chemosphere 87(4): 333–338. http://dx.doi.org/10.1016/j.chemosphere.2011.12.017


Metal pollution e.g. copper, in water bodies occurs worldwide. Although copper is an essential trace metal, at certain levels it is still considered as pollutant. The aim of this study was to investigate the effect of exposure concentration on copper bioaccumulation in marbled crayfish (Procambarus sp.) by determining uptake and elimination kinetics. Crayfish were exposed to sub-lethal copper concentrations (average measured concentrations of 0.031 and 0.38 mg Cu L−1) for 14 d and transferred to copper-free water for another 14 d. At different time points during the uptake and elimination phases copper concentrations were measured in five organs (exoskeleton, gills, muscle, ovaries and hepatopancreas). At 0.031 mg Cu L−1, copper levels in the crayfish organs were not significantly increased compared to the control animals, suggesting effective regulation. Exposure to 0.38 mg Cu L−1 did lead to not significantly increased copper levels in muscles and ovaries, while the gills and exoskeleton, which are in direct contact with the water, showed significantly higher copper concentrations. In these four organs, copper showed fast uptake kinetics with equilibrium reached within 10 d of exposure. Copper accumulation was highest in the hepatopancreas; uptake in this storage organ steadily increased with time and did not reach equilibrium within the 14-d exposure period. Copper accumulation levels in the marbled crayfish found in this study were hepatopancreas > gills > exoskeleton > muscle.

Keywords: copper • toxicokinetics • bioaccumulation • hepatopancreas • marbled crayfish

19 April 2012

Crawling out of the swamp May 1st!

Get your donations ready!

10 April 2012

SciFund 2: Return of the Marmorkrebs!

You may recall that last year, I had a Marmorkrebs project in the inaugural SciFund Challenge.

I’m pleased to report that Marmorkrebs and I will both be back in the next SciFund challenge, starting in May.

But not together.

Kyle MacLea will be carrying the banner for Marmorkrebs in Round 2. To learn more, you should follow Kyle’s blog, By Way of Science. He’s also on Twitter and Google Plus.

This is an opportune time to update people on the status of the project I successfully launched in round 1. I contacted some experts on Procambarus fallax in Florida, and the answer I got was consistent. The best time to collect for that species was... November. News will be slow on the first #SciFund project, then.

As for my own project in SciFund 2, you can read about it over at my other blog, NeuroDojo.

05 April 2012


Last year, I live-blogged the announcement that Gerhard Scholz had been award The Crustacean Society’s Excellence in Research Award. He was not at the meeting to accept his award, but the latest issue of Journal of Crustacean Biology discusses his research contributions in more detail and allows him to reply. I am pleased to see it does not leave out Marmorkrebs.

In 2003, Gerhard reported the first parthenogenetic decapod, a cambarid crayfish (Marmorkrebs) found in the aquarium trade. It was subsequently shown that these animals originated in Florida, and molecular evidence revealed that they were in fact a form of Procambarus fallax that has established itself in several European countries as well as Madagascar, thus uncovering a harmless pet primed to become a devastating invasive species.

In his comments, Dr. Scholz offers this bon mot:

Life without crustaceans is possible, yet pointless!


McLay C, Boyko CB, Schram FR. 2012. Gerhard Scholtz Recipient of the Crustacean Society Excellence in Research Award. Journal of Crustacean Biology 32(2):341-344.

29 March 2012

Might we finally get a crayfish genome?

I just learned of a new project, Arthropods Genomes, which aims to sequence 5,000 arthropod genomes. The project wiki is here, which includes a form to suggest species to include for sequencing.

No need to rush. I suggested Marmorkrebs for sequencing before I started writing this post.

This should be no surprise, given that a crayfish genome is something I’ve been asking for for years. Indeed, every time someone mentions how bored they are with yet another genome being sequenced, or how hard it is for the poor genome researchers who are drowning in so much data, it’s become a running joke for me to say, “Yeah, yeah... So where’s my frickin’ crayfish genome

As of this writing, four decapod species are in the draft list. The Lousisiana red swamp crayfish, Procambarus clarkii, is on the draft list of species. This is a good choice, as we know more about its biology than probably any other crayfish.

I hope this pans out.

Related posts

Olivia’s fantasy genomes
Genome research: Good idea, bad idea
The first crustacean genome

Hat tip to Ed Yong and Alex Wild.

23 March 2012

Crayfish chemistry? Publishing error, or just added value?

Around March 19, I got an alert for a new Marmorkrebs article appearing in PubMed. It is a very interesting article about a Marmorkrebs with some male characteristics.

I was surprised by the journal, which was not one I recognized. “Biomaterials science”? Well, I suppose crayfish could be inspiration for biomaterials. I went to the link out...

Polymer edition? I was even more puzzled. There didn’t seem to be anything in the abstract about biomaterials, and especially not polymers.

One of the authors of the paper, Gerhard Scholz, confirmed that the article wasn’t supposed to be in Journal of Biomaterials Science, but Journal of Crustacean Biology. I kept watching all week for what would happen to the article.

By Friday, the article was appearing in the “Fast track” section on IngentaConnect for Journal of Crustacean Biology. The DOI for the article didn’t change.

The PubMed entry, however, still points to the polymer journal. How or when that will be updated, I don’t know, but I’ll keep checking.

This raises the question of how publishers should correct mistakes. Retraction Watch blog has a section devoted to retractions cause by “publisher error.”  Here, there has been no retraction, or notice, or explanation to the readers of Journal of Biomaterials Science - Polymer Edition. True, the error was short-lived, and the critical identifier – the DOI – was stable.

The case of the PubMed ID will be interesting to watch, because Journal of Crustacean Biology is not normally indexed in PubMed. As far as I can discover, there is only one other article (“Effect of microgravity and hypergravity on embryo axis alignment during postencystment embryogenesis in Artemia franciscana (Anostraca),” PMID: 11539283) from the journal’s history in PubMed. Whether the article will stay in PubMed, have the corrected citation information, and have the PubMed ID will stay the same, remains to be seen.

16 March 2012

German video

Some excellent crayfish photography here in this German language video interview with Gerhard Scholtz.

09 March 2012

Sintoni and colleagues, 2012

Sintoni S, Benton JL, Beltz BS, Hansson BS, Harzsch S. 2012. Neurogenesis in the central olfactory pathway of adult decapod crustaceans: development of the neurogenic niche in the brains of procambarid crayfish. Neural Development 7: 1. http://dx.doi.org/10.1186/1749-8104-7-1


Background: In the decapod crustacean brain, neurogenesis persists throughout the animal’s life. After embryogenesis, the central olfactory pathway integrates newborn olfactory local and projection interneurons that replace old neurons or expand the existing population. In crayfish, these neurons are the descendants of precursor cells residing in a neurogenic niche. In this paper, the development of the niche was documented by monitoring proliferating cells with S-phase-specific markers combined with immunohistochemical, dye-injection and pulsechase experiments.

Results: Between the end of embryogenesis and throughout the first post-embryonic stage (POI), a defined transverse band of mitotically active cells (which we will term ‘the deutocerebral proliferative system’ (DPS) appears. Just prior to hatching and in parallel with the formation of the DPS, the anlagen of the niche appears, closely associated with the vasculature. When the hatchling molts to the second post-embryonic stage (POII), the DPS differentiates into the lateral (LPZ) and medial (MPZ) proliferative zones. The LPZ and MPZ are characterized by a high number of mitotically active cells from the beginning of post-embryonic life; in contrast, the developing niche contains only very few dividing cells, a characteristic that persists in the adult organism.

Conclusions: Our data suggest that the LPZ and MPZ are largely responsible for the production of new neurons in the early post-embryonic stages, and that the neurogenic niche in the beginning plays a subordinate role. However, as the neuroblasts in the proliferation zones disappear during early post-embryonic life, the neuronal precursors in the niche gradually become the dominant and only mechanism for the generation of new neurons in the adult brain.

Keywords: None provided.

29 February 2012

Marmorkrebs return to Nature

Marmorkrebs made their official “debut” to the English speaking scientific world in Nature, so I’m pleased that they are back in the pages of that journal, even if only in a small way. An article on poster sessions used a Marmorkrebs poster from last year as an illustration.

The article is available for free at the Nature Jobs website.


Powell K. 2012. Billboard science. Nature 483: 113-115. http://dx.doi.org/10.1038/nj7387-113a

14 February 2012

Vogt, 2012

Vogt G. 2012. Ageing and longevity in the Decapoda (Crustacea): a review. Zoologischer Anzeiger 251(1): 1-25. http://dx.doi.org/10.1016/j.jcz.2011.05.003


Ageing and longevity is a neglected field of crustacean biology. Information on longevity is available for less than 2% of the extant species of the Decapoda. Maximum ages reliably determined range from 40 days to 72 years corresponding to a life span difference of a factor of 650. The shortest-lived decapods are planktonic dendrobranchiate shrimps, and particularly long-lived species with life spans of decades are found in the Astacidea. Most decapods seem to live for 1–10 years. High geographical latitude, the deep sea and freshwater caves promote longevity. The majority of the Decapoda is indeterminately growing and presumably characterized by negligible senescence. The adults of the determinately growing decapods like some brachyuran crabs suffer from mechanical senescence and are unable to regenerate lost appendages. The decapod crustaceans have developed many effective anti-ageing mechanisms including moulting, detoxification of free radicals, removal of cellular waste, renewal of tissues by life-long stem cell activity, regeneration of appendages, detoxification of environmental pollutants and isolation of pathogens and diseased tissue areas by melanisation and encapsulation. Age related diseases including cancer are virtually unknown. The present compilation of data on longevity and senescence in decapods is the first one that covers the whole spectrum of a higher invertebrate taxon. It is hoped to provide an interesting source of information for carcinologists and biogerontologists. Further improvement of knowledge on ageing and longevity in the Decapoda would be beneficial for crustacean aquaculture, fisheries and ecological modelling. Some decapods even have good potential to become models for general ageing research.

Keywords: Decapoda • life span • senescence • growth format • anti-ageing mechanisms • stem cells • biogerontology

Stloukal, 2009

Stloukal E. 2009. Recent distribution of non-indigenuous (sic) crayfish species in Slovakia. Folia faunistica Slovaca 14(19): 119-122. http://zoology.fns.uniba.sk/ffs/14-2009/19/stloukal-2009.htm


Two non-indigenuous (sic) crayfish species (NICS) widely spread though Europe (namely spiny-cheek crayfish (Orconectes limosus) and signal crayfish (Pacifastacus leniusculus)). Few other invasieve (sic) species do occur intemittent (sic) in water bodies of souther (sic) nad (sic) western part of the country.

Keywords: None provided.

Note: The map of Marmorkrebs introductions has been updated to include this record of a breeding population in Slovakia.

07 February 2012

Call for papers: The Crustacean Society 2012 summer meeting

Yup, conference season is not all that far away. So here’s a reminder that the summer meeting of the Crustacean Society is going to be held in Greece this June.

The last day of abstract submission is 29 February 2012. The last day for early registration (= reduced participation fees) is 31 March 2012.

Probably a little too far apart to go to this, then stay in Europe to the end of August to make the crayfish meeting in Austria.

31 January 2012

Call for papers: 19th Freshwater Crayfish Symposium

The 19th International Symposium on Freshwater Crayfish (IAA19) is now accepting registrations and presentation abstracts. The meeting will be held in Innsbruck, Austria, at the University of Innsbruck from 26-31 August 2012.

Please note that discounted meeting registration fees (€30) are only for active members of the International Association of Astacology (IAA). So if you’re not a member, or have not renewed your membership, now’s the time to pay up!

Go to the meeting website at: http://www.uibk.ac.at/ecology/events/iaa19/index.html.en

24 January 2012

The eight most popular crayfish

Those keeping crayfish as pets might be interested in Chris Lukhaup’s round-up, Freshwater Aquarium Crayfish.


12 January 2012


Anyone need a new desktop wallpaper?

Rough translation: “My army of marbled crayfish will be invincible.”