29 December 2009

2009 was tied for the best year ever in Marmorkrebs research

I’m going to take a risk that another paper about Marmorkrebs is not going to come to my attention in the next three days.

I admit to being a little disappointed, because I thought around this time last year that the line would be continuing an upward trend, rather than staying flat.

23 December 2009

Invertebrate Rearing, a new journal

A new journal is a tricky thing to get up and running, so I am pleased to plug Invertebrate Rearing. Editor Ed Baker is getting the first issue ready to go, and you can still get something in for the first issue if you submit by 10 January 2010.

This journal may have in an unfilled niche in the realm of animal care professionals. My impression is that most of the journals in this field tend to focus mammals or fish, with those working on fish usually having a strong aquaculture emphasis rather than research.

Collecting invertebrates

There has been plenty of reason to discuss the pet trade on this blog, mainly in the context of accidental release of unwanted pets like crayfish. It is just as important to realize, however, that there are also problems at the other end of the pet trade pipeline. For that reason, I wanted to put in a quick pointer to a new article on invertebrate collection for the pet trade. You can also find a brief summary at the Conservation Maven blog.

22 December 2009

If Cosmo had a crayfish edition

One of my students informed me that she’d seen a crayfish in a recent issue of news stand favourite, Cosmopolitan.* This got me thinking about the kind of articles that might be accompanying the photo...

The best SEX you’ve NEVER had: Is parthenogenesis for you?”

Marbled is the new black: Sexy crustie winter colours”

“Jet set: The glamorous life of an invasive species”

“Swamp fever: The truth about hybridization”

“Do these claws make my uropods look fat? Dieting and your rigid exoskeleton”

10 swimmeret secrets that will drive him wild!”

* I was unable to get a copy of the original picture, because I was not comfortable reading through every page of Cosmo while standing in the line at Wal-Mart.

16 December 2009

Crayfish of Crater Lake

Just a quick pointer to the Wild Muse blog, which has a nifty story about Native American legends about crayfish in Crater Lake, and the real species living there.

15 December 2009

Crayfish in Canada

I’ve updated the web page listing North American laws on crayfish to include all the Canadian provinces. It appears that Manitoba, Saskatchewan, and Ontario have laws concerning crayfish use, with Manitoba and Saskatchewan having fairly broad prohibitions.

While I’m here, I’ll note that I’ve moved the files for the main websites, Marmorkrebs.org and MarbledCrayfish.org, from a commercial server to one provided by my academic institution. This change should be unnoticeable, but there’s always the possibility that things will get confused in the transition. If you want to make sure you’re seeing the most recent files, the direct link is:


08 December 2009

Genome research: good idea, bad idea

ResearchBlogging.orgGood idea: A paper in the Journal of Heredity proposes sequencing 10,000 genomes...

Bad idea: ...of vertebrates.

Okay, I’ll admit that isn’t strictly a bad idea. But it certainly leaves something to be desired, given that a news article in Science characterized this plan as, “No genome left behind.” But of course, it leaves a tremendous number of genomes behind, namely, every single invertebrate. What are the current estimates for number of vertebrate species? Maybe 60,000 or so? The crustaceans alone probably have about the same number of species. The number of vertebrate species is not even close to the number of beetle species.

The paper provides no rationale for doing such a massive scan of the vertebrate genomes alone as opposed to a project that would include the invertebrates. Indeed, the word “invertebrates” appears only once, in reference to fisheries.

In fairness, I actually do think it’s great that these researchers are working together and suggesting a big, bold scheme. I’ve made no secret that I want a crayfish genome project. With this 10K genome paper, maybe it’s time to start thinking about a larger scale invertebrate genome sequencing project that will cover the rest of the animal kingdom, even though it’s obviously not possible to do the same level of coverage as the small vertebrate sub-phylum.


Genome 10K Community of Scientists. (2009). Genome 10K: A Proposal to Obtain Whole-Genome Sequence for 10 000 Vertebrate Species Journal of Heredity, 100 (6), 659-674 DOI: 10.1093/jhered/esp086

Pennisi, E. (2009). No Genome Left Behind Science, 326 (5954), 794-795 DOI: 10.1126/science.326_794

05 December 2009

Pic of the moment: 5 December 2009

This is a sick crayfish. As readers may know, I am not a pathologist or parasitologist, so I have little idea what these black spots may be or how to combat them. We’ve definitely had some animals die prematurely due to whatever these are. Any information would be most welcome!

24 November 2009

Darwin on crayfish development

Today is the 150th anniversary of the publication of On the Origin of Species. I’ve talked before about the monograph on crayfish by Darwin’s close friend, Thomas Henry Huxley, but Darwin himself did significant work with crustaceans, notably barnacles. But because this is a crayfish blog, I went looking through the massive online database of Darwin’s writing for references to crayfish.

In the Variation of Plants and Animals Under Domestication:, Darwin considers something near and dear to the heart of this blog, crustacean development:

We are led to the same conclusion, namely, the independence of parts successively developed, by another and quite distinct group of facts. It is well known that many animals belonging to the same class, and therefore not differing widely from each other, pass through an extremely different course of development. Thus certain beetles, not in any way remarkably different from others of the same order, undergo what has been called a hyper-metamorphosis—that is, they pass through an early stage wholly different from the ordinary grub-like larva. In the same sub-order of crabs, namely, the Macroura, as Fritz Müller remarks, the river cray-fish is hatched under the same form which it ever afterwards retains; the young lobster has divided legs, like a Mysis; the Palæmon appears under the form of a Zoea, and Peneus under the Nauplius-form; and how wonderfully these larval forms differ from each other, is known to every naturalist. Some other crustaceans, as the same author observes, start from the same point and arrive at nearly the same end, but in the middle of their development are widely different from each other.

In other words, Darwin has twigged to the important idea that each stage of the life-cycle of an organisms is under different selective pressures, and thus one stage can diverge while the others remain quite similar.

Crayfish are also mentioned in one of Darwin’s transmutation notebooks. In it, Darwin shows his admiration for the natural world (“beautiful adaptations”), and interest in explaining the non-adaptive features (“unintelligible structures”):

The question if creative power acted at Galapagos it so acted that birds with plumage and tone of voice purely American, North and South; so permanent a breath cannot reside in space before island existed. Such an influence must exist in such spots. We know birds do arrive, and seeds. (And geographical divisions are arbitrary and not permanent. This might be made very strong, if we believe the Creator created by any laws, which I think is shown by the very facts of the Zoological character of these islands.)

The same remarks applicable to fossil animals same type; armadillo-like cray [i.e., crayfish?] created; passage for vertebrae in neck same cause. Such beautiful adaptations, yet other animals live so well. This view of propagation gives a hiding place for many unintelligible structures; it might have been of use in progenitor, or it may be of use,—like mammae on man's breast.

In the Voyage of the Beagle, crayfish feature in a segment that shows the less enlightened aspect of Darwin’s cultural background, with the sort of references to “savages” that interested colonial powers.

The little stream, besides its cool water, produced eels and cray-fish. I did indeed admire this scene, when I compared it with an uncultivated one in the temperate zones. I felt the force of the observation, that man, at least savage man, with his reasoning powers only partly developed, is the child of the tropics.

More on Darwin’s ties to crustaceans can be found in today’s post on NeuroDojo.

17 November 2009

For your consideration

The nomination deadline for The Open Laboratory anthology, the annual collection of science writing on blogs, is in two weeks. If there’s a post from this blog that you liked, I’d like to ask that you consider nominating it for the anthology. Posts from 1 December 2008 to 30 November 2009 are eligible.

Some suggestions, in chronological order:

Click here to submit an entry. A Blog Around the Clock regularly updates the list of entries; here’s a recent one (probably out of date by the time you read this).

In case you’re wondering why I don’t just nominate myself, I think it’s better for readers to decide what’s good than writers. And because it feels gauche to nominate a bunch of your own stuff.

12 November 2009

A whiter than white way to get rid of invasive crayfish

Got a crayfish invasion? Try bleach. A lot of it.

10 November 2009

A panoply of embryos

The September 2009 issue of Genesis features a gorgeous array of animals early in their development, taken by students at the Woods Hole embryology course. The journal says that one of the images is of marbled crayfish, but doesn’t exactly provide a key.

I emailed the course organizers, and Nipam Patel got back to me, writing:

I should say that after looking again, it would be best to say that it is definitely a decapod crustacean, but it might actually be a crab larvae instead. I say this because the student who did the staining was working with a number of decapods (multiple crayfish and crab species) at the time and I am not certain that this image is actually Marmokrebs.

And, for the record, the crustacean is immediately under the words “Genetics and” in the subtitle, and is purple and green. Even if it isn’t Marmorkrebs... it’s still a superb cover.

03 November 2009

Circus of the Spineless #44

Welcome to the 44th and latest edition of Circus of the Spineless, the monthly celebration of animal diversity. Although this blog is devoted to just one invertebrate species, I’m pleased to host this carnival and showcase all the other wonderful forms that invertebrates take. Please take a moment to visit the home page and have look around.

I find the biggest problem is always how to sort the posts. Sadly, I am not imaginative, so I broke it down into the nicknames that I often hear my colleagues who study invertebrates: “crunchies” (things with exoskeletons) and “squishies” (things with soft bodies).

Crunchy posts

Because this is a crustacean blog, please forgive a little double favouritism by me starting off with a post from NeuroDojo (a sibling blog that I also author). In it, I take serious ethological research on hermit crabs, and turn it into a fairy tale.

Not only do I love fairy tales, I love mysteries, too. It can be a simple mystery, like “Who’s easting the Photinias?” Jason at Xenogere takes on the case and gets photographic evidence.

Adrian at The Bug Whisperer also tries to take photos, but seems to cause a crime rather than preventing one, as a fight breaks out between his ant subjects. Models can be such divas.

Staying with ants for the moment, the Wild About Ants blog shows ants visiting extrafloral nectaries on cacti. Roberta Gibson want to know if you’ve seen ants visiting nectaries; go help her out.

At Hill-Stead’s Nature Blog, Diane Tucker features dragonflies and envies their ability to rise above it all.

Trees, Plants and More catches photos of a lynx spider among some plant leaves.

Marcia Bonta looks at charismatic invertebrates. And I guess if you’re an invertebrate and want to be charismatic, it helps to have long legs, since she focuses in on daddy long legs and stick insects.

But if you want beautiful, Ted MacRae at Beetles in the Bush reckons he’s got the most beautiful beetle on the North American continent. I took the liberty of including a picture at right; isn’t it a beauty?

Wandering’ Weeta also has a gallery of insects who take advantage of her warm home in fall.

At The DC Birding Blog, John discusses and documents several insects lured by the promise of cheap beer. I am not making this up. If that’s a little to crazy for you, just look at the nice butterflies.

Another birding blog, 10,000 Birds momentarily joins the spineless celebration with carpet moths.

Dave Ingram, writing on the modestly titled Dave Ingram’s Natural History Blog, rounds out the crunchy section of our program with some pictures and note on millipedes.

Squishy posts

Wanderin’ Weeta finds a jellyfish in a tide pool, and gets the event on camera.

Trees, Plants and More serves up a hammerhead worm in the “More” category.

While I would never claim to have saved the best for last, I do think you’ll admit this last post is worth the wait. Hill-Stead’s Nature Blog brings us... slug poetry!

Next time, on Circus of the Spineless...

That concludes this installment of Circus of the Spineless! Please join us again in about 30 days over at Greg Laden’s Blog. Email your submissions to Greg. (And come on, squishy lovers, show your colours!)

27 October 2009

Great moments in crayfish music: The Soul Cages

This may be the only song in living memory by a major musician to mention crayfish in the lyrics.

Listen to the first verse, and you’ll hear:

And the chaos of cages where the crayfish lie

20 October 2009

Vogt, 2009

Handbook on LongevityVogt G. 2009. Research on aging and longevity in the parthenogenetic marbled crayfish, with special emphasis on stochastic developmental variation, allocation of metabolic resources, regeneration,
and social ctress. In: Bentely JV, Keller MA (eds), Handbook on Longevity: Genetics, Diet and Disease, pp. 353-372. Nova Science Publishers: Hauppauge.
ISBN: 978-1-60741-075-1


This article presents first results on aging and longevity in the marbled crayfish, an isogenic invertebrate with indeterminate growth. The marbled crayfish is the only known parthenogenetic species of more than 10.000 decapod crustaceans and has a maximal life span of roughly 3.5 years. Its main advantages, aside from genetically identical offspring and lifelong growth, are the alternation of growth and reproduction phases, a high regeneration capacity and easy handling in the laboratory. In a group of seven genetically identical batch-mates life span varied from 437 to 910 days although the sibs were communally reared and fed ad libitum with the same pellet food. In the same group there was no clear-cut relationship between longevity and growth or reproduction frequency. However, the specimen with the lowest life span showed fast growth, early onset of reproduction, and short time intervals between reproduction cycles. Damages like loss of appendages were repaired and did not negatively affect longevity. Social stress, in contrast, shortened life expectancy. The biological peculiarities of the marbled crayfish and the data obtained so far argue for a more intense use of this animal in research on aging and longevity.

Keywords: None provided.

13 October 2009


ScoopThe most recent paper concerning Marmorkrebs says:

While this manuscript was being prepared, Jones et al. (2008) (sic) published an account of a molecular study identifying crayfish specimens collected in Madagascar as Marmorkrebs.

Kawai and colleagues are pleasant about it in the paper, but the bottom line is that they got scooped. While they were themselves scooped, they unwittingly also scooped another author, namely me.

I’d been doing some preliminary work on a morphological description of Marmorkrebs, for the same reason presented in the new paper: to aid identification. While I wasn’t terribly far along in the process, I did have data recorded. It was more than just an idle, “Oh, I’ll do it some day.”

Crustacean biology has both the blessing and curse of usually being a slow-moving field. Progress is measured in years and decades rather than months. This means that scoops are rarely an issue. The Marmorkrebs story is one that has moved unusually fast, and those of us working with this organism probably need to take account of that.

I’ve also conducted and published research on ascidians, and I was impressed me by how that research community seemed organized and generally cohesive. At their meeting, they would arrange informal “working groups” to cooperatively plot out some of the research plans so that the projects in different labs were complementing rather than competing. The ascidian community realized there are benefits to community and communication.

There is more than enough research on Marmorkrebs to do that there should be some way to ensure that we don’t waste time duplicating our efforts.

12 October 2009

Oh dear... Madagascar not worried about crayfish, for wrong reasons

Back in March, I wrote:

Sadly, an invasive crayfish species is currently a very small problem for researchers and others concerned with the island. The country is in turmoil politically.

Half a year hasn’t improved matters much. A new piece in New Scientist says political instability is continues to threaten Madagascar’s biological treasures.

Since a military coup forced the president to resign in March, conservationists and biologists have watched as loggers have stripped the country’s forests and killed its animals for bushmeat. ...

(A)t the very least, 120 rosewood and ebony trees, worth an estimated $480,000, are being taken out of Masoala, Madagascar's largest national park, each day. At least thirteen illegal traders, known locally as the “rosewood Mafia,” buy the wood and export it, mostly to China. Conservationists say the logging is destroying the island’s national parks and having knock-on effects on the forest's animals.

Emphasis added.

06 October 2009

Submit to Circus of the Spineless!

Next month, I am pleased to host the Circus of the Spineless carnival on this blog. Submit your squishy and / or crunchy blog links to me throughout October, so we’ll be ready to roll at the start of November!

29 September 2009

Kawai and colleagues, 2009

Kawai T, Scholtz G, Morioka S, Ramanamandimby F, Lukhaup C, Hanamura Y. 2009. Parthenogenetic alien crayfish (Decapoda: cambaridae) spreading in Madagascar. Journal of Crustacean Biology 29(4): 562-567. http://dx.doi.org/10.1651/08-3125.1


Invasion of an alien freshwater crayfish is newly confirmed in Madagascar. The invasive crayfish is determined as the parthenogenetic Marmorkrebs (marbled crayfish) (Cambaridae: Decapoda) on the basis of morphological features and the fact that all collected specimens were females regardless of their size. As this is a worrisome finding, the public should be alerted so that spread on the island can be prevented before it affects the vulnerable native crayfish biodiversity and the rice field business in Madagascar.

Keywords: alien species • Madagascar • Marbled crayfish • morphology • parthenogenetic species

(Note: What the abstract does not mention is that this paper contains the first detailed description of Marmorkrebs morphology. This should greatly aid identifications, since many species of Procambarus superficially resemble Marmorkrebs, particularly in the marbled colouration.)

22 September 2009

Marmorkrebs on the road: Texas A&M University

The whiteboard announcing our talkA day driving, a day talking, a day driving. That pretty much sums up a recent visit to Texas A&M University last week, where I had been invited to give a talk to the Applied Biodiversity Sciences program.

This was fun and interesting in a few ways. At the suggestion of the organizer, my student Stephanie and I gave a joint talk, which isn’t all that common. I did the first third, she did the middle, and I returned to handle the last third.

We also left the audience wondering how we got PowerPoint to do all the zooming. The answer was that we didn’t use PowerPoint for our visual aids. Instead, we were experimenting with some new software called Prezi. If you do presentations, you probably have a few months where it’ll be really cool before everyone else discovers it.

The biggest surprise was that a couple of audience members had direct ties to Marmorkrebs. One sold them in Switzerland back in the 1990s. Another confirmed something that I’ve only heard as a rumour, namely that Marmorkrebs are being aquacultured in China. More to follow on these leads, no doubt.

Thanks very much to everyone in these pictures for coming to our talk!

15 September 2009

An experiment gone wrong in Hong Kong?

ResearchBlogging.orgI was re-reading the recent paper on the introduction of Marmorkrebs in Italy (Marzano et al., 2009), and noticed this:

In their publication on (sic) Nature, the authors even raised the hypothesis that Procambarus sp. is a transgenic species created by laboratories in Hong Kong.

The only Nature paper featuring Marmorkrebs to date is the first one (Scholtz et al., 2003). I freely admit that I miss things, and do not remember everything. But the paper is only one page, so a statement like that would be hard to miss. And I’d like to think I would have remembered a claim that Marmorkrebs were the result of a scientific experiment gone wrong.

I re-read the Nature paper. The words, “Hong Kong” do not appear in it. There is a brief mention of transgenics, but it is in a comment saying that Marmorkrebs would be good for transgenic experiments in the future, not that they were the result of transgenic experiments in the past. For a moment, I wondered in the reference cited (Nam et al., 2000) next to the comment about Marmorkrebs’ potential was from a Hong Kong lab, but the authors of that paper all gave South Korea as their country of origin.

The origin of this comment is almost as puzzling at the origins of Marmorkrebs itself.

Marmorkrebs already sound like they’ve stepped straight out from a science fiction potboiler. You cannot work with an invasive species of female clones (which Marmorkrebs is) without at least thinking of old monster movies or pulp magazines. If they were truly an escaped science experiment? And “made in Hong Kong” to boot? Forget my next grant proposal... I’m going to work on my screenplay.

(I’d cast Michael Praed to play me in the move.)


Marzano FN, Scalici M, Chiesa S, Gherardi F, Piccinini A, & Gibertini G. 2009. The first record of the marbled crayfish adds further threats to fresh waters in Italy Aquatic Invasions 4(2): 401-404 http://dx.doi.org/10.3391/ai.2009.4.2

Nam YK, Cho, YS, Kim DS. 2000. Isogenic transgenic homozygous fish induced by artificial parthenogenesis. Transgenic Research 9(6): 463-469. http://dx.doi.org/10.1023/A:1026596422225

Scholtz G, Braband A, Tolley L, Reimann A, Mittmann B, Lukhaup C, Steuerwald F, & Vogt G. 2003. Parthenogenesis in an outsider crayfish. Nature 421(6925): 806-806. http://dx.doi.org/10.1038/421806a

08 September 2009

Olivia’s fantasy genomes

The always articulate Olivia Judson looks at genome projects in her recent New York Times column, and asks what organisms should be on the list to have their genome sequenced. She makes a persuasive case for the famous “living fossil,” the deep sea coelacanth.

The reader comments contain many good nominees (whales, naked mole rats, potato blight, and more), but I’m afraid I was not selfless. I wrote in the comments:

Coelacanth is an excellent choice. It could be difficult to get enough tissue, given that they are such elusive creatures.

I want to argue for a crayfish genome.

Crayfish (and their relatives, lobsters and other decapod crustaceans) are commercially important. They are harvested for food and cause ecological and economic damages as invasive species to name just two reasons.

Crayfish are important model organisms for research, particularly neurobiology. Discoveries made in crayfish include electrical synapses, presynaptic inhibition, and neuromodulation of aggression.

Crayfish are the current record holder for highest number of chromosomes in an animal (Pacifastacus leniusculus: 2n=376).

There is only one crustacean genome (a small freshwater one, Daphnia pulex). In comparison, about a dozen insect genomes are complete and more are on the way.

Probably the best choice of species would be Louisiana red swamp crayfish (Procambarus clarkii), because it is common, spread across the globe, and well studied.

The mysterious crayfish Marmorkrebs could be an interesting second choice, because their origins are unknown, and they are the only known decapod crustacean where all the individuals are female.

01 September 2009

Power chords for power crays

I think you’ll agree that the choice of music for this clip is... unexpected.

29 August 2009

Disclaimer, disclaimer, disclaimer

Just in case there is any confusion, I have nothing to do with the Marmorkrebs Twitter feed. I post as DoctorZen there.

25 August 2009

Glad we humans have an endoskeleton...

Because having to ditching your entire skeleton to grow would be no fun at all.

Because the clip is interesting, I’m happy to overlook the spelling of “molting” in the title.

20 August 2009

Marmorkrebs on the road: ESA 2009

Stephanie Jimenez presenting her latest poster at the Ecology Society of America meeting in Albuquerque recently.

11 August 2009

Great moments in crayfish research: Before he was famous

Sigmund FreudToday’s post is a bit of a cheat, because the research is not as well known as the researcher who performed it. Nevertheless, it’s fun to look back into the history of crayfish research and find none other than Sigmund Freud, he of psychoanalysis, dream interpretation, and much more.

In his 20s, Freud was a comparative neurobiologist. His doctoral dissertation was on fish spinal cords. Freud later worked in the lab of Ernst Brücke. There, Freud studied crayfish and freshwater crabs.

Freud’s contribution was apparently quite significant... although it’s sometimes hard to work out exactly what that contribution was. Those of us who do not read German can’t read the original paper, and must rely on the translations of others to get an appreciation of the context and significance of the work. I’ve read Freud’s crayfish described in various ways, ranging from showing that the axons were connected to cell bodies to showing that neurons contained a cytoskeleton.

Freud's drawing of crayfish neuronsUnfortunately, Freud found that research didn’t pay enough for him to get married, so he went into medical practice. And that was the start of the twisting road leading to the work that Freud is best known for.

Given the controversies over Freud’s later work in psychology, however, one could make the case that both biology and psychology might have been better off if Freud stayed a neurobiologist.

Interestingly, Freud was far from alone in starting a research career in invertebrates before becoming famous in psychology.

Jean Piaget worked on snail behaviour, publishing papers while he was still in high school, before his studies on how children think made him the premiere developmental psychologist.

Alfred Binet did his doctoral work on insect nervous systems, which was later overshadowed by his development of one of the first intelligence tests.


Sigmund Freud's place in the history of the neuronal cytoskeleton
The Life and Times of a Ten-legged Cannibal
Freud was a pioneering neuroscientist (Added 10 March 2014)

05 August 2009

Brief cameo in American Scientist

American Scientist, September 2009This blog makes a brief cameo appearance in the “Members in the News” section of the new issue of American Scientist. I guess they used the subtitle because “Marmorkrebs” alone was too cryptic...

04 August 2009

Conferences 2.0

The Ecological Society of America conference is now on. Remember to visit the Marmorkrebs poster on Friday morning, poster PS 88-134.

The question of whether conferences are worth it is worth revisiting. The Byte-Size Biology takes a look at several online science tools, including virtual conferences, and concludes that the virtual conference is not ready yet.

First: virtual conferencing technology sucks. It doesn’t matter if you use a free Skype on a $150 netbook, or a state-of-the art teleconferencing equipment with a 52″ screen and Dolby Surround, piped through at hundreds of Gigabits per second. You will get interruptions, cuts, lags, annoyances and embarrassing moments. Second: social reasons. The important parts of a conference take place in the hallways, poster sessions, meals, banquets and, of course, the pub across the street. Incipient collaborations, exchange of ideas, brainstorming: all those take place around the dinner table and in the halls. With food, coffee and alcohol providing the social lubrication, and the talks and posters the intellectual one. A conference is much more than a series of talks.

28 July 2009

Swimmerets with eggs

21 July 2009

Pic of the moment: 21 July 2009

Molting... almost done!

(Low resolution picture because this was snapped with my phone. Sorry, but these gals are hard to catch in the act.)

14 July 2009

Countdown to the IAA Eighteenth Symposium

InsectsThe Eighteenth Symposium of the International Association of Astacology (IAA) is being held about one year from now at the University of Missouri. It will be running 18-23 July in 2010.

The main conference page is here. I am hoping to have some Marmorkrebs research to show at that conference.

How can you resist a meeting that guarantees attendees “expansion of your mental, physical, and spiritual being” and, I quote, “plenty of nuisance insects”?

07 July 2009

Great moments in crayfish research: Muscle receptor organs

Jerzy Stanislaw AlexandrowiczSome artists create with paint. Some artists create with sound. Some artists create with words. Jerzy Stanislaw Alexandrowicz was an artist who created with methylene blue.

Methylene blue is a straightforward vital stain, and many kids school use it today to see cells under a microscope. But Alexandrowicz took the simple stain to new scientific heights. An obituary gives some idea of his mastery, describing his technique as “legendary,” and his skills so renown that scientists from all over came to visit his lab to learn his methods. (The obituary, incidentally, is well worth reading and paints a picture of a rather remarkable man.)

Alexandrowicz first noted small sensory organs in the tail of crustaceans in the 1930s, but didn’t get to finish the work until after World War II, and published the discovery until 1951. He termed these “muscle receptor organs” (MROs) because the neurons were indeed sitting along a very fine strip of muscle. I doubt the PDF does justice to the pictures in the original paper, but one can get a sense of just how detailed he was. The attentive may object to this being called a “Great moment in crayfish research,” because Alexandrowicz worked with lobsters. Although the muscle receptor organs weren’t originally described in crayfish, almost all of the work that followed was done in crayfish.

Muscle receptor organFrom the outset, there was interest in these little sense organs because they were readily accessible, sitting just underneath the exoskeleton and on top of the large fast flexor muscles. In contrast, similar looking organs in mammals, muscle spindle organs, were buried deep in muscles and very difficult to work with. There has been much work on them because of that, and I can only hope to hit a few highlights here.

Cornelius “Kees” Wiersma and colleagues (1953) quickly started doing physiology on these little sense organs, and explicitly drew parallels between them and vertebrate sense organs. They found that the two sensory neurons in the muscle receptor organs had very different properties. One was tonic, responding to slow and small changes, and tended to fire all the time. The other one was phasic, responding only to very hard flexions of the abdomen, and then only for one or two spikes. Wiersma and colleagues continued to do the basic legwork of tracking down the basics of the circuit (Hughes and Wiersma 1960).

Because of the neuronal connections, and the responses of isolated neurons in the dish, Larry Fields (1966) proposed that the muscle receptor organs acted in load compensation (pictured below is Figure 8 from his paper). That is, the muscle receptor organs appeared to be wired so as to detect the difference between how much bending of the tail the animal was trying to do, and how much was actually occurring. If there was a difference between those two, a reflex would kick in, activating extensor muscles to compensate for the impeded movement.

This worked with in a dish.

Unfortunately, when the muscle receptor organs were recorded from live animals performing load compensation, it seemed that the muscle receptor organs didn’t actually work that way (McCarthy and Macmillan 1999). So the function of the muscle receptor organs in intact animals, even after 50 years of work in many labs, still remains to be fully understood.

The muscle receptor organs are an “evergreen” scientific preparation, and I’ve hit on only a very, very small number of papers on them here. That I can only touch on these few highlights in a blog post is a nice example of how often, science is not about breakthroughs, but inch by inch progress.


Alexandrowicz JS. 1951. Muscle receptor organs in the abdomen of Homarus vulgaris and Palinurus vulgaris. Quarterly Journal of Microscopical Science 92: 163-199. PDF

Fields HL. 1966. Proprioceptive control of posture in the crayfish abdomen. The Journal of Experimental Biology 44: 455-468. http://jeb.biologists.org/cgi/content/abstract/44/3/455

Hughes GM, Wiersma CAG. 1960. Neuronal pathways and synaptic connexions in the abdominal cord of the crayfish. The Journal of Experimental Biology 37: 291-307. http://jeb.biologists.org/cgi/content/abstract/37/2/291

McCarthy B, Macmillan D. 1999. Control of abdominal extension in the freely moving intact crayfish Cherax destructor I. Activity Of the tonic stretch receptor. The Journal of Experimental Biology 202(2): 171-181. http://jeb.biologists.org/cgi/content/abstract/202/2/171

Wiersma CAG, Furshpan E, Florey E. 1953. Physiological and pharmacological observations on muscle receptor organs of the crayfish, Cambarus clarkii Girard. The Journal of Experimental Biology 30(1): 136-151. PDF

02 July 2009

Marzano and colleagues, 2009

Aquatic Invasions logoMarzano FN, Scalici M, Chiesa S, Gherardi F, Piccinini A, Gibertini G. 2009. The first record of the marbled crayfish adds further threats to fresh waters in Italy. Aquatic Invasions 4(2): 401-404.


The red swamp crayfish, Procambarus clarkii, is the most abundant invasive crustacean decapod in Italy. Evidence is however emerging for the presence of other Cambaridae that are erroneously assigned to the P. clarkii taxon. The marbled crayfish, belonging to a still uncertain species of the genus Procambarus, has been found for the first time in Italy in the Canale Maestro della Chiana (Tuscany, Central Italy), where it lives in sympatry with a large P. clarkii population. Although a single specimen was found, this record is particularly relevant due to the parthenogenetic reproductive habit of the marbled crayfish. However, molecular analyses based on COI barcoding did not reveal any differentiation within the P. clarkii population and excluded any form of hybridization between the two species. We will shortly discuss new pathways of invasive species and the threats posed by parthenogenetic species, even though they seem to be still sporadic.

Keywords: barcoding • conservation • marbled crayfish • parthenogenesis • nonindigenous species

30 June 2009


MarmerkreeftLast week, I mentioned that Marmorkrebs have been found in the Netherlands. This newsletter has more details (PDF format; I had problems getting it to open automatically, but was able to save it from my web browser). You may find it useful, particularly if your Dutch is better than mine.

According to Google Translate, the pictured page roughly means:

English Marbled crayfish
Originally area not known
Natural habitat habitat unknown. The species is only known from the aquarium trade (where the species probably also created).
Dissemination in The Netherlands in 2004 for the first found in an old Griend in Dordrecht (the lay).

27 June 2009

And they’re in the Netherlands, too

Received an email today pointing out a few references that show Marmorkrebs have been showing up in the waters of the Netherlands for some time now. The one below is a starting point:

Holdich DM, Pöckl M. 2007. Invasive crustaceans in European inland waters. In: Gherardi, F. (ed) Freshwater bioinvaders: profiles, distribution, and threats, pp. 29-75. Springer: The Netherlands. ISBN 978-1-4020-6028-1 (hardcover); ISBN 978-1-4020-6029-8 (ebook). Google Books

16 June 2009

Pic of the moment: 16 June 2009

The annulus ventralis of Marmorkrebs. This feature is on the underside of the animal near the most posterior legs, and is sometimes found in crayfish species descriptions.

09 June 2009

Marmorkrebs on the road: ESA 2009

There will be a Marmorkrebs poster in the late-breaking poster session of this year’s annual Ecological Society of American meeting in Albuquerque, New Mexico. This will be presented by Stephanie A. Jimenez. This poster is her third presentation this year, all on different aspects of Marmorkrebs (she’s been busy!).

All late-breaking posters will be presented on Friday, 7 August 2009. Drop by and say hi!

02 June 2009

Map of the world

View Marmorkrebs introductions in a larger map.

The main Marmorkrebs.org page lists an in-press paper describing a case of Marmorkrebs being found in a natural ecosystem. I’ve mentioned Madagascar before, and now Italy has been added to the list. The Italy article hasn't been posted in the blog yet, because I like to include articles here only once they have final pagination and so on.

It seems reasonable to expect more such reports in the future. I’ve created a Google map to start documenting where Marmorkrebs are reported. I will update it as often as I get information.

26 May 2009

Are they a problem if people eat them?

Procambarus clarkiiA new report described in the Telegraph lists marbled crayfish as posing “high risk” to British wildlife if they are released into the wild.

This news story comes on the heels of two letters in the most recent issue of Science that offer a back and forth on the issue of introduced species. The first, by Gozan and Newton, talks about potential benefits of introduced species, like “aquaculture, sport fishing, forestry, horticulture, and game hunting.” The reply by Hulme and colleagues mentions crayfish as an example:

Major aquaculture species such as the crayfish Procambarus clarkii and Pacific cupped oyster Crassostrea gigas threaten endemic species through predation, competition, and/or the spread of diseases, and these two specific examples are widely recognized as some of the worst invasive species in the region(.) ... The history of biological invasions in Europe has too many examples of shortsighted decisions targeting perceived economic gains that have resulted in much larger (and often irreversible) costs to society. Thus, such “balance sheet” decision-making promoted by Gozlan and Newton, rather than a precautionary approach, is not only naïve but potentially dangerous.

This article on the National Science Foundation website has an related take on invasive species. It tracks students who were examining the impact of Louisiana red swamp crayfish (Procambarus clarkii) into China.

(W)e were surprised by how welcome this exotic crayfish was in the Chinese community, even among rice farmers whose crops were being destroyed. ...

Another rice farmer explained that if he had the necessary resources, he said he would sell only crayfish and eliminate rice farming all together.

Emphasis added. This is particularly relevant to Marmorkrebs, as it has been rumoured that they are being investigated for aquaculture purposes in China. Plus, asexual species in theory can generate double the number of reproductive offspring every generation compared to sexual species.

Thus, people could be extremely tempted to introduce Marmorkrebs into natural ecosystems deliberately. The problem is that such introductions have ended in tears as often, if not more often, than they have ended in triumph. (Two words: Cane toads.)

Harvested crayfish in Chinese fish market. Difficult to recognize, except for escapee in upper left!

22 May 2009

Jones and colleagues, 2009

Jones JPG, Rasamy JR, Harvey A, Toon A, Oidtmann B, Randrianarison MH, Raminosoa N & Ravoahangimalala OR. 2008. The perfect invader: a parthenogenic crayfish poses a new threat to Madagascar’s freshwater biodiversity. Biological Invasions 11(6): 1475-1482.


In 2007 an unusual crayfish found in food markets in the capital of Madagascar was preliminarily identified as Procambarus ‘Marmorkrebs’: a new world taxa and the only decapod known to reproduce by parthenogenesis. We present information on the identity, distribution and ecology of this recent invader and attempt to evaluate the threat it poses to Madagascar’s biodiversity and to livelihoods. The species appears to be currently limited to the area close to Antananarivo, but is being sold alive on major transport routes. We present molecular evidence of its taxonomic relationships and confirm that the Procambarus present in Madagascar is indeed the parthenogenic taxa. We investigate its reproductive ecology and find Procambarus ‘Marmorkrebs’ to have an extremely high fecundity; more than six times that of the native crayfish Astacoides. The limited evidence we have suggests that this species poses a serious threat to freshwater biodiversity and that it is likely to damage human livelihoods (through its impact on fishing and possibly rice agriculture). More research is urgently needed but in the meantime action is needed to reduce the rate of spread before it is too late.

Keywords: AphanomycesAstacoides • exotic • invasive species • marbled crayfish • Procambarus

19 May 2009


Marmorkrebs crayfish
Are parthenogenetic.
Males are not needed.

12 May 2009

In the newsletter

March issue of Crayfish NewsMarmorkrebs.org makes a brief cameo appearance in the latest Crayfish News newsletter with an article called, “Crayfish Blogging and Citizen Science.” The newsletter is a publication of the International Association of Astacology (password protected for members).

05 May 2009

How big is the pet trade?

In the new issue of Science, Smith and colleagues present some interesting information on import of wild animals.

Over half a million shipments of wildlife containing >1.48 billion live animals have been imported by the United States since 2000. ... The majority (92%) of imports were designated for commercial purposes, largely the pet trade.

Yup, that’s billion with a “b.”

The authors specifically comment on HR 669.

In its current form, H.R. 669 does not consider the economic benefits of wildlife trade. We argue that it should. H.R. 669 requires evaluation of the threat imported wildlife species pose as invasive species or carriers of known pathogens before importation. It proposes creation of lists of species “approved” or “unapproved” for import. Although the Act recognizes that there are species for which adequate scientific and commercial evidence is not yet available to make an evaluation of import risk, it does not stipulate how such species should be handled. For these species, we propose that H.R 669 should require their temporary placement on a “gray list.” These gray-listed species should receive priority funding for risk analysis.

Subcommittee hearings have been held, but no report has been made.


Smith KF, Behrens M, Schloegel LM, Marano N, Burgiel S, Daszak P. 2009. Reducing the risks of the wildlife trade. Science 324(5927): 594. doi: 10.1126/science.1174460

28 April 2009

If you want to say Marmorkrebs in Japanese


At least, I can only assume that says either “Marmorkrebs” or “marbled crayfish.” I have no idea how that would be pronounced phonetically. I found it at the top of a gallery of Marmorkrebs pictures can be found here. Many useful links are embedded with the pictures.

21 April 2009

New rules?

HR669 hasn’t exactly been making national headlines, but in certain circles, has been the topic of much discussion. Sponsored by Guam delegate Madeleine Bordallo (pictured), it’s going to be the subject of an American congressional subcommittee hearing this week (23 April 2009).

The summary of the bill indicates that much is expected in determining whether a species would be allowed in the country or not, including the identity of the organism to the species level and the native range of the species.

Of course, Marmorkrebs would pose a potentially interesting enforcement conundrum. It has no formal species description. It has no known native range – but its closets relative appear to be southern U.S. species. Are Marmorkrebs nonnative?

GrrlScientist has several posts about this new bill (first, second, third).

There are literally tens of thousands of species of non-native birds, mammals, reptiles, amphibians, fish and invertebrates that are kept and bred in the United States (for example, there are more than 2,500 species of non-native freshwater and marine fish species in the aquarium trade alone).

In particular, she is asking researchers for information about whether this would impact their research.

Mike Dunford chimes in here and has a follow-up here.

14 April 2009

Rare, threatened, or endangered?

I was listening to an interview with Sarah Pryke on The Science Show. She works with beautiful Gouldian finches (a gallery of them is here). It came up in the conversation that she has about 2,000 of these birds. She estimates that this may well be equal to the number of these birds left in the wild. Which is one of those astonishing thoughts. We forget how many species have most, if not all, of their populations essentially reliant on humans keeping them.

What do you call an animal with no known original wild population? “Extirpated”? No, that’s not quite right. “Extinct in the wild”? That assumes that there is an identified wild population. Regardless, an organism that had known no endemic territory left would be surely be worthy of a conservation effort, wouldn’t it?

Of course, Marmorkrebs fall into such category. We don’t know if they have a home besides our aquaria, or whether it’s under threat or how many Marmorkrebs there might be.

I’ve written a fair amount about Marmorkrebs’ potential to be an invasive species. And while they’ve been introduced into the wild, in Madagascar and elsewhere, but it is far too early to tell what the outcome there will be. If anything, there should probably be some efforts to try to control them in places like Madagascar, because they so obviously don’t belong there.

Nevertheless, it is worth considering the idea that Marmorkrebs might actually be rare, in the global sense. Unless we find a wild population – and there are some reasons to suspect that one might not exist – their future might depend on humans.

And being in that situation has rarely worked out well for the organisms concerned.

07 April 2009

23 Squidoo

Marmorkrebs are now featured on a Squidoo lens and The Aquarium Wiki.

I find it fascinating how the picture I uploaded for Wikipedia makes its way elsewhere around the web.