30 December 2008

2008 was the best year ever for Marmorkrebs research

Marmorkrebs publications graph
Scientific publications on Marmorkrebs are showing a promising trend, with 50% more papers this year than last.

Of course, it's not really fair to throw around phrases like "50% increase" when the numbers are still quite small. But I hope that in one year's time, I'll be able to say that 2009 was the best year ever for Marmorkrebs research. The graph above does not include two papers still in press, which means that we're up two papers for 2009 already. That puts us about a third of the way towards another record breaking year before it even starts!

Additional, 10 January 2009: I just realized that the graph I posted is slightly wrong. I somehow miscounted the number of papers in 2007. I know, I know... "He can't count to five?" Sorry. But in science, the best thing is always admit error and try to fix it.

The correct graph is to the right. 2008 saw a 20% increase in Marmorkrebs papers from the previous year, not 50%.

29 December 2008

The new phonebook is here!

This blog is now listed in the Nature.com blog list. Right below the more imaginatively named, "Monday Begins on Saturday" (a sentiment I fully appreciate, by the way).

I know blogging about being listed in a directory is a bit like Steve Martin's joy over the new phonebook in The Jerk (below), but this is about as close as I'll probably ever get to having something in Nature, so I shall enjoy it.

24 December 2008

There must have been some magic in that old filter they found...

As a scientist, I am not allowed to invoke magic or miracles in my explanations, no matter what time of the year it is.

Nevertheless, this does seem an appropriate time of year to report the some people say that marbled crayfish are magic.

Had a tank, completely empty for the past month if not longer. Just put water in it again two days ago. Turned on the light today and there staring back at me was a marble crayfish.

First of all, I thought I had sold all of them a long time ago like a month before I moved, secondly, even when I had them, I never kept them in this tank. Perhaps she was living in one of the sponge filters I put in there? But that has been out of water for over a month as well! I dont know what to think. maybe she's magic?

Marmorkrebs also feature in this blog entry this blog entry, "Are there really virgin births?" Although I've jokingly used the phrase before, the thought creeps into mind if attaching an egg to a swimmeret should really be considered birth.

23 December 2008

Marmorkrebs on the road: SICB 2009

SICB logoYour webmaster will again be attending the Society for Integrative and Comparative Biology meeting in Boston in early January. And this time, I'm bringing an actual research poster about Marmorkrebs from our lab, titled "Establishment of a research colony of Marmorkrebs, a parthenogenetic crayfish species," and Stephanie Ann Jimenez (seen here), my REU student, to present her work.

Come visit our poster P2.150 in the Grand Ballroom on Monday, 5 January in the session "Neurobiology II: Neurophysiology and Behavior" from 3:00 to 5:00 pm.

22 December 2008

Mistaken identification?

A recent question over in Yahoo! Answers points out one of the problems of using the name "marbled crayfish" to describe Marmorkrebs. Previously, I wrote:

(T)here are no doubt many species of crayfish that could be described as "marbled."

Since writing that, I got another species in my lab (which I haven't keyed out yet) with a very similar marbling pattern to Marmorkrebs, but which is definitely not Marmorkrebs. There are a few key differences in morphology, and the animals tends to a more orange hue than Marmorkrebs.

Similarly, looking at the picture in the Yahoo! Answers, I agree that it's marbled, but I don't think I agree that it's Marmorkrebs. The pattern of marbling looks wrong, particularly on the tail. It's the sort of thing that is very difficult to quantify.

16 December 2008

Season's greetings

If your Christmas cards are not sufficiently crustacean inspired, click here for a PDF of a Christmas card you can print out and mail to your friends or attach to their presents.

You may also want to check out last year's Christmas greeting if you're still looking for more festive cheer.

09 December 2008

Fabritius-Vilpoux and colleagues, 2008

Invertebrate NeuroscienceFabritius-Vilpoux K, Bisch-Knaden S & Harzsch S. Engrailed-like immunoreactivity in the embryonic ventral nerve cord of the Marbled Crayfish (Marmorkrebs). Invertebrate Neuroscience 8(4): 177-197.


The homeobox transcription factor Engrailed is involved in controlling segmentation during arthropod germ band formation but also in establishing individual neuronal identities during later embryogenesis. In Crustacea, most studies analysing the expression of Engrailed so far have focussed on its function as segment polarity gene. In continuation to these previous studies, we analysed the neuronal expression of the Engrailed protein by immunohistochemistry in the embryonic nerve cord of a parthenogenetic crustacean, the Marbled Crayfish (Marmorkrebs). We paid particular attention to the individual identification of Engrailed expressing putative neuroblasts in the crayfish embryos. Engrailed positive cells in the neuroectoderm were counted, measured and mapped from 38 to 65% of embryonic development. That way, several Engrailed positive putative neuroblasts and putative neurons were identified. Our findings are compared with earlier studies on Engrailed expression during germ band formation in Crustacea. Recent data on neurogenesis in an amphipod crustacean have provided compelling evidence for the homology of several identified neuroblasts between this amphipod and insects. The present report may serve as a basis to explore the question if during crustacean neurogenesis additional communalities with insects exist.

Keywords: neurogenesis • neuroblasts • ventral nerve cord • neurophylogeny • evolution • Arthropoda • Tetraconata • Crustacea

Procambarus clarkii clones?

A paper making a quite surprising claim snuck out back in August. Yue and colleagues, collecting Procambarus clarkii in China, claim to have found genetically identical individuals. They found 15 individuals that are genetically identical to at least one other individual in their sample of 120. This provides evidence of cloning in this very commonly used lab species. This is highly surprising if true, since there have been no shortage of labs working on P. clarkii over the years.

Doubtless more to come on this story!


Procambarus clarkiiYue 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

Great moments in crayfish research: Stochastic resonance

In one of those end-of-the-year "Top 10" lists that are so popular, New Scientist compiled a list of its top 10 brain articles. As I scanned through the list, I spotted one that I knew had a crayfish connection: "Does the brain feature built-in noise?"

When you type "crayfish" into Google Scholar, the first two hits, with over 600 citations each, both relate to noise, and they concern one experiment. The first contains a review of the second, so the second paper, by Douglass and collegues (1993), is the primary article.

The paper is about stochastic resonance in crayfish.

Yup. That one's going to take some explaining.

Imagine you're on the ground, trying to pick apples off an apple tree on a completely calm, windless day. You can only reach (or jump!) so far, and the apples on the branch remain just out of reach.

Now imagine the same scenario, but instead with a little gust wind blowing. Now the branches, instead of staying still, start to sway in the breeze. And just once in a while, that extra push from the breeze puts an apple close enough that you can grab it. That random movement of gusty wind actually helped accomplish something. That's much like stochastic resonance.

Of course, there will be limits to this. If the wind gets too severe, the branches of the apple tree will be flailing around so much that grabbing an apple will get harder and harder, not easier.

The New Scientist article put it like this:

Noise is usually a nuisance, as anyone who lives under a flight path or has tried to listen to a distant AM radio station can testify. But to engineers it can be a godsend, and now its benefits are cropping up in biology, too. More than a decade of research suggests that under some circumstances, a small injection of noise can sharpen up the way in which an organism senses its environment. For example, crayfish are better at detecting the subtle fin movements of predatory fish when the water is turbulent rather than still.

Resonance graphThe experimenters recorded from sensory hairs (sometimes called tactile afferents) on the tailfan of crayfish. These small hairs are very sensitive to water movement, and feed into various systems, including the escape response system. In the escape system (and no doubt neurons), no one sensory cell has a big enough signal to reach the threshold for the next cell in the chain to fire. Thus, a little random noise in the environment actually makes the sensory hairs more likely to fire the target neurons, because the noise pushes the system a little closer to threshold overall. And the authors performed experiments showing that this actually occurs with real neurons in real animals. That's what the graph shows: the best signal (Y axis) is here there's a little noise, not at the lowest noise level (X axis).

It's not at all intuitive, yet it's probably very common in biological and non-biological systems. And that combination is arguably why this is one of the most cited crayfish papers in biology.


Douglass JK, Wilkens L, Pantazelou E, & Moss F. 1993. Noise enhancement of information transfer in crayfish mechanoreceptors by stochastic resonance. Nature 365(6444): 337-340. http://dx.doi.org/10.1038/365337a0

02 December 2008

Fish and crayfish

Pet storeAlthough this blog is focused on science, I do occasionally get questions about Marmorkrebs as pets, which is great. I am planning on doing a little frequently asked questions list on pet care, but here's a couple of thoughts for those keeping Marmorkrebs as pets.

Marmorkrebs do best at room temperature (20°C). If you have Marmorkrebs in with some tropical fish in a heated tank, the crayfish may not fare as well.

Marmorkrebs are generally not aggressive. Still, most crayfish are not picky eaters, and would probably grab at another fish in the tank if they had the chance. And conversely, some big fish might find crayfish tasty and attack, particularly after molting.

14 November 2008

If you liked something in this blog...

The Open Laboratory 2008 is a competition for science writing in blogs. The current list of nominees is here, and yes, I self-nominated a post from this year from this blog. If there was a post this year you liked, you might consider mentioning it by this form.

Glorious movies of zebrafish development

This week, Science published an article about zebrafish development. The article, however, does not do justice to the joyous, glorious movies that it is about. Single frames don't do -- you really have to see these things in motion.

Check it out here. I think many people will find them fascinating, even non-biologists. The early stages show near-simultaneous cell divisions making the embryo pulse, while the later stages show cells rolling around the embryo like fireworks obeying some strange alternate laws of gravity.

Since zebrafish represent the kind of work that Marmorkrebs are very good for -- development -- the natural question to ask is, can similar approaches be applied to Marmorkrebs eggs? Hard to say. Zebrafish embryos are quite transparent, whereas Marmorkrebs embryos are more yolky and therefore opaque. But many things are possible, and this technology might be able to visualize at least parts of what's going on.

The follow-up question might be, "Can I play with those great toys?" The "toys" in this case is their modified confocal microscope that made this possible. Alas, not possible for me, since the team hails from Germany.

Zebrafish frame grab 2

31 October 2008

Pic of the moment: 31 October 2008

Astacopsis gouldi

A monster crayfish for Hallowe'en!

Although I lived in Australia for a couple of years, one of my few regrets is that I never got to Tasmania, where this beast lives. Astacopsis gouldi is the biggest crayfish -- indeed, the biggest freshwater invertebrate -- in the world.

From old news story here.

28 October 2008

The devil herself

She-Devil movie posterThread title is taken from a caption underneath a picture of Marmorkrebs in an excellent post over at the Amphidrome blog about the recent discovery of Marmorkrebs in Madagascar. In particular, it notes of the native Madagascar crayfish species, which belong to the genus Astacoides:

(H)abitat loss and overharvesting have hit (Astacoides) crosnieri and A. petiti hard enough to earn them endangered status on the IUCN Red List.

Many good references there, too.

21 October 2008

The obstacles to asexuality

BioEssaysOne of the few things about the origin of Marmorkrebs that appears indisputable is that it evolved from a sexually reproducing species. An new review paper in BioEssays examines some of the obstacles that an organism has to overcome to switch from sexual to asexual reproduction. As such, it surely lays our a lot of the conceptual groundwork for research on the origin of Marmorkrebs.

Engelstädter J. 2008. Constraints on the evolution of asexual reproduction. BioEssays 30(11-12): 1138-1150. http://dx.doi.org/10.1002/bies.20833

17 October 2008

Vogt, 2008c

Vogt G. 2008. How to minimize formation and growth of tumours: Potential benefits of decapod crustaceans for cancer research. International Journal of Cancer 123: 2727–2734.


Tumours have only rarely been observed in the decapod crustaceans, a large animal group of more than 10,000 species that includes the commercially important and well investigated shrimp, lobsters, crayfish and crabs. Analysis of the literature and information from cancer and diseases data bases revealed a total of 15 incidences, some of them being questionable. Even in the long-lived species, which can reach life spans of almost 100 years, neoplasias are virtually unknown. The data published so far suggest that the strikingly different frequencies of carcinogenesis between decapods and other well investigated animal groups like mammals, fish, insects and molluscs is based on differences of the metabolic pathways for carcinogens, the immune systems, and the regulation of stem cells. Therefore, representatives of the Decapoda may serve as useful models to study how organisms can successfully prevent or control spontaneously and environmentally induced cell proliferation. A particularly promising candidate for in-depth investigation of these topics is the marbled crayfish, a rather new clonal lineage that is presently being introduced as a laboratory model in development and epigenetics.

Keywords: neoplasia • Decapoda • Crustacea • stem cells • detoxification of carcinogens • age-related cancer • immune system • epigenetics • marbled crayfish

14 October 2008

Artistic merits

An artist with the handle Marmorkrebs has a piece on the deviantART website.

10 October 2008

From small acorns

I haven't been blogging a lot, because I'm teaching some very time consuming classes this semester (one in particular is wailing on me). So just a quick one for now...

I wanted to pass on a tip from Frederike Alwes (coauthor of this paper), who informed me that Marmorkrebs like oak leaves in their tanks, both as food and for making the water perhaps a bit more acidic. We're trying it out in our lab now.

30 September 2008

Wiring the -ome

NeuronBank is a project I have been offering moral support to, mainly in the form of links here and there around the Marmorkrebs websites I run. The goal of NeuronBank is to compile the "neurome" for organisms, mainly invertebrates.

Most people are familiar with the concept of a genome: the sum total of all the genes in an organism. Since the success of the Human Genome Project, other "-ome" projects have been slowly creeping into scientific awareness. Arguably proteomics is one of the most common new -omes in the scientific news. Neuromes -- a description of all neurons in an animal -- are not in that league yet, but that may start to change.

A forthcoming new review by Lichtman and Sanes in Current Opinion in Neurobiology goes one step further, discussing not only neuromes, but connectomes: a description of not only all the neurons in a nervous system, but their anatomical and physiological connections, too.

If that sounds difficult, it is, but it's already been done in one animal: the little nematode worm C. elegans. The C. elegans project is discussed in some detail -- which it has to be, seeing how it's the only animal in the connections between all 302 neurons in the wild-type animal has been described.

While there is no complete neurome or connectome for a crustacean, there are neuromes and connectomes for parts of crustacean nervous systems. The stomatogastric ganglion in several species has about 30 neurons, and all the neurons and all the connections in the stomatogastric ganglion are known for some crabs and lobsters, thanks largely to work in Allen Selverston's lab. This has led to a massive amount of research on the stomatogastric ganglion. Literally entire books have been written on the subject (Harris-Warrick, 1992; a PDF of the first chapter is available here).

The crustacean cardiac ganglion, which usually has 9 neurons, may also have a complete circuit worked out for it, though I have been unable to confirm this in writing this post. In any case, it is well characterized (Cook, 2002).

But are other parts of the crustacean nervous system amenable to compiling a even a partial neurome, never mind a connectome? I think so, and suggest crayfish abdominal ganglia are ripe for creating a neurome.

Crayfish abdominal ganglion by RetziusThe tail of a crayfish contains six clusters of nerve cells (a.k.a. ganglia). The first five from the front are very similar, and only the very last one, the terminal abdominal ganglion, is substantially different than the others. The abdominal ganglia of crayfish are widely used for electrophysiology, because the dissection is very simple. Wine (1984) estimated that there are about 650 neurons in each of the first five abdominal ganglia.

650 is not that big a number of neurons. And a reasonable number of them are already described. Given a few dedicated labs, creating a neurome for these ganglia seems at least feasible.

In one of my earliest posts on this blog: Every major model organism has earned that rank on the back of a massive descriptive project. I've already said there should be a crayfish genome project; a crayfish neurome project should be in the works, too.


Cooke IM. 2002. Reliable, responsive pacemaking and pattern generation with minimal cell numbers: the crustacean cardiac ganglion. The Biological Bulletin 202: 108-136. http://www.biolbull.org/cgi/content/full/202/2/108

Harris-Warrick RM, Marder E, Selverston AI, Moulins M (eds.). 1992. Dynamic Biological Networks: The Stomatogastric Nervous System. Cambridge: MIT Press.

Lichtman JW & Sanes JR. 2008. Ome sweet ome: what can the genome tell us about the connectome? Current Opinion in Neurobiology: In press. http://dx.doi.org/10.1016/j.conb.2008.08.010

Wine JJ. 1984. The structural basis of an innate behavioural pattern. The Journal of Experimental Biology 112: 283-319. http://jeb.biologists.org/cgi/content/abstract/112/1/283

24 September 2008

Men only

Men Only magazineMarmorkrebs are interesting partly because of their parthenogenesis. But if the idea of a on sex species seems strange when it's a female, you ain't seen nothin' yet. The always entertaining Olivia Judson has a column up in the New York Times about a different kind of parthenogenesis: the kind where only the males' genes get into the next generation.

09 September 2008

Pic of the moment: 9 September 2008

The feather-like plumes on the side of this animal's carapace are actually her gills. It seems the gills somehow got stuck on the outside of her carapace during molting. It's unusual looking, but apparently not terribly harmful, as this individual is generally continuing to show good health.

Photo by Zen Faulkes.

02 September 2008

Laws and claws

GavelIn hopping around some of the forums where Marmorkrebs have been mentioned, a recurring question has come up about the laws on keeping and shipping crayfish. Is is legal to have Marmorekrebs, to ship them to another country, and so on.

I don't know. I've seen some comments that in the U.S., the rules about importing and keeping crayfish vary from state to state. I haven't done an exhaustive search on this, but it's come up a few times, so I think I may have to do it sometime soon.

Second, this is one of those times where science moves faster than law. This actually happens fairly often. A particularly interesting example was when a court had to rule on whether whales were fish. Marmorkrebs weren't known to science until a few years ago, still doesn't have a proper species name, still not known if it exists in the wild (other than where it has been introduced). I imagine that makes it sort of difficult to draft laws concerning it. But the law usually catches up...

28 August 2008

Vogt, 2008b

Vogt, G. 2008. The marbled crayfish: a new model organism for research on development, epigenetics and evolutionary biology. Journal of Zoology 276(1): 1-13. http://dx.doi.org/10.1111/j.1469-7998.2008.00473.x


Model organisms have contributed significantly to the understanding of basic biological phenomena. Suitable animal models are at hand for some research disciplines like genetics, development and cell biology but are still sought after for others like epigenetics. Research of the last years has revealed that the marbled crayfish (Marmorkrebs), which was discovered in the mid-1990s, meets researchers' demands for a vigorous, genetically identical and eurytopic laboratory model very well. Its most prominent advantages are production of high numbers of genetically identical offspring, stepwise alteration of the phenotype by moulting, complex morphology and behaviour and sequential generation of segments and limbs. This paper first reviews the discovery and research history of the marbled crayfish, its biology and culture and its special advantages. It then discusses, based on the published data, its suitability as a laboratory model for various research disciplines. The greatest potential of the marbled crayfish lies in epigenetics and environmental epigenomics and in stem cell research and regeneration. The marbled crayfish also appears to be suitable for the investigation of the role of stochastic developmental variation and epigenetic inheritance in evolution and to contribute to evo-devo and eco-devo. This unique crayfish is even of some value for applied biologists, for example as a toxicological test species.

Keywords: Marmorkrebs • model organism • development • epigenetics • environmental epigenomics • evolution • regeneration • stem cells

26 August 2008

Failed models, Part 2

Back in the 1960s, there was a lot of research interest in little flatworms, Planaria. They were being used as model organisms in research on learning and memory.

On the face of it, Planaria shared many advantages with other model organisms: it's small, easy to look after, and common. The field had its own journal, The Worm Runner's Digest, (later the Journal of Biological Psychology).

But I suspect you'd be hard pressed to find anyone using Planaria today as a general model organism. Indeed, there's a book titled, Whatever happened to Planaria? So why did Planaria fail as a model organism? I will confess to not having read the book above, but I can see a few reasons.

First, a major finding based on Planaria was... well.. weird. Basically, if you taught one animal something (like running a maze), then killed it and fed the pieces to another animal, it performed better at the task than expected. Much was written about this, and I think the bottom line is that it didn't replicate well. It didn't lead to useful experiments in other species. In some sense, this one claim may have discredited the field.

Second, as a model for learning and memory, Planaria were being studied just at a time when electrophysiology started to make huge progress in understanding the neural basis of learning. And here, Planaria are not convenient: they and their neurons are a bit small for electrophysiology. The sea slug Aplysia, on the other hand, had huge nuerons, and it filled the niche of a simple invertebrate model for studying learning.

Third, I can't help shake the impression that the field was somewhat insular. Maybe this is just an impression I get from The Worm Runner's Digest, at least. I don't know where a lot of other Planaria research at that time was published. This is the downside of having specialty journals on one organism: other people don't read it. If you're going to have a model organism, this is lethal.

To this day, though, The Worm Runner's Digest is justly remembered for its irreverent humour.


Alvarado AS. 2004. Planarians. Current Biology 14(18): R737-R738. http://dx.doi.org/10.1016/j.cub.2004.09.005

Mitman G, Fausto Sterling A. 1992. Whatever happened to Planaria? C.M. Child and the Physiology of Inheritance. Princeton University Press: Princeton.

19 August 2008

Failed models, Part 1

I was listening to an interview with Courtney Humphries, the author of Superdove: How the Pigeon Took Manhattan ... And the World on the Scientific American podcast. The book is about pigeons, and part of the book concerns the amount of scientific research done on pigeons.

Pigeons have been the subject of several major biological research programs. Perhaps most famously, Charles Darwin talks at some length about pigeons and pigeon fanciers in On the Origin of Species. Fancy pigeons interested Darwin because they came in so many forms, yet were all descended from a common rock dove. If a few breeders with a few generations could cause such changes in form, imagine what Nature could do with vastly more time, Darwin argued.

Pigeons were also used in many key learning experiments by B.F. Skinner. Superdove talks about one of the stranger applications of this -- a proposed pigeon guided missile -- but the weirdness of that should not distract from how much they taught Skinner about learning mechanisms.

Then there's a branch of research about animal navigation, and clearly homing pigeons have contributed large amounts of knowledge there.

Yet despite these significant contributions, pigeons are not really considered a standard model organism in science today. Arguably, they could have been. But today, arguably the most prominent model organisms for animals are the fruit fly species Drosophila melanogaster, the mouse species Mus musculus, and the nematode worm species Caenorhabditis elegans. For plants, it's Arabiopsis thaliana.

Why did these win and pigeons not? The big four listed above were all model organisms for genetics. They were among the first to have a complete genome sequenced. And with the rise of molecular biology, that is a tremendous facilitator for research.

If Marmorkrebs have any hope of becoming a model organism for researchers, there needs to be a crayfish genome project.

18 August 2008


Made a couple of little link banners for use in web ages in a few spare moments.

White on black banner

Black on white banner

11 August 2008

Forum hopping

Although I haven't been blogging a huge amount, there's actually been a fair amount of stuff I've been doing behind the scenes, as it were.

In one of those little coincidences, Marmorkrebs have suddenly become the topic of conversation on several different pet discussion forums (see here and here). I've been sticking my head in to provide what information I can, and particularly to suggest that anyone who wants to keep these be careful about it.

Again, I would ask that anyone who is a hobbyist with Marmorkrebs to email me. I just want to get a sense of when they made it into North America in the pet trade.

I also made a few little updates to the main page. In particular, I highlighted two new articles, one of which I just got this morning. I list articles "in press" on the home page before they show up in the blog. I publish abstracts on the blog when they have their final volume, page number, and so on.

08 August 2008


I received over 70 new Marmorkrebs yesterday. This should help get a stable reproductive colony up and running much faster and with less worry on my part.

29 July 2008

Fishing hobbyists

This thread at an angling website has me nervous. Using Marmorkrebs as live bait seems to be a very poor idea, since the whole point is, well, to introduce the thing into a wild habitat while it's still alive. Admittedly, they're not supposed to get away, but it seems a lot easier for them to get away when they're in a lake or a river than when they're in a tank in your living room.

It's worth nothing that the International Society of Astacology recommended over 20 years ago that governments try to find ways to prevent crayfish from being imported for things like bait.

Again, I invite anyone who knows of these being sold as bait in North American to email me. I just wish to get a sense of how these things are being distributed.

22 July 2008

Calling all crayfish pet owners

I now have two fairly reliable reports of fish hobbyists in North America with Marmorkrebs. These two cases are quite distant from each other geographically. I am very interested in tracking the spread of these animals through the pet trade in North America.

If you have any marbled crayfish as pets, please email me.

15 July 2008


EndNoteI've made a link to an EndNote X library containing all peer-reviewed Marmorkrebs articles on the Marmorkrebs main page.

Other reference managers are available, as they say in public broadcasting. If anyone wants reference compilations to other formats, let me know and I'll see what I can do.

08 July 2008

Unnamed threats

The newest issue of Current Biology has a very good primer on crustaceans in general. It contains a very brief mention of Marmorkrebs:

The recent finding of a parthenogenetic crayfish strain in the aquarium trade also poses a potential threat if it makes its way into the wild.

Unfortunately, there are no references, nor any attempt at naming the crayfish, making this perhaps a somewhat cryptic reference to a novice reader -- which is exactly who this article is directed at!

As readers of this blog will know, it is no longer an "if" as to whether Marmorkrebs makes its way into the wild. It already has done. Such is the curse of lead time (the delay between when something is written and when it appears in print).


VanHook AM, Patel NH. 2008. Crustaceans. Current Biology 18(13): R547-R550. http://dx.doi.org/10.1016/j.cub.2008.05.021

Great moments in crayfish research: Presynaptic inhibition

Presynaptic inhibitionNeurobiology is fundamentally about cellular communication. Cells communicate in several ways, but in neurons, the primary way that neurons communicate with each other across synapses. Synapses are, strictly speaking, the physical gaps between neurons, but the term is often loosely expanded include the cellular machinery to send and receive signals across that gap. If you understand synapses, you're a long way towards understanding brains and all they do.

Crayfish have made a big impact on our understanding of synapses. In 1976, Harold Atwood wrote:

The largest part of our available knowledge of the mechanisms of chemical synaptic transmission comes from work on vertebrate (especially frog) neuromuscular synapses. Probably the synapses between the giant fibers of the squid would rank second in significance, while third place would go to the neuromuscular synapses of crustaceans.

There were many reasons why the connections between neurons and muscles in crustaceans made such a big impact on our understanding of synaptic physiology. Detailing them all would take several posts, but it sort of boils down to three factors.

First, the muscle cells are huge.

Second, there are only a few neurons connecting to muscles.

Third, the connection between neurons and muscles in crayfish is not like the connection between neurons and muscles in mammals.

If you ever took a basic physiology course, you probably learned two things: that neurons only excite muscles, and that how many neurons are fired controls how much a muscle contracts. This is true for mammalian skeletal muscle, but it's not true for crustaceans.

In crustaceans, some neurons inhibit muscles, and the pattern of neurons firing plays a much bigger role in determining how much a muscle contracts. Consequently, synapses between neurons and muscles in crustaceans are much more like synapses in brains than the highly specialized synapses between neurons and muscles in mammalian skeletal muscle. Mammalian muscle synapses are, to be blunt, quite boring.

All this is preamble to the actual discovery mentioned in the title of this post.

Neurons continually communicate with each other, but they don't necessarily act on that communication. Neurons are the kings of filtering out mixed messages. Typically, a neuron receives a conflicting mess of excitatory and inhibitory signals. By adding them all up, it determines whether to fires (sending a signal to the next neuron) or not. Thus, inhibition occurs on the receiving end, which is said to be postsynaptic.

Using crayfish claw muscles, Josef Dudel and Steve Kuffler found an entirely different way that neurons can inhibit signals. Rather than sending an inhibitory signal to a neuron directly, they found one neuron could "intercept" a signal that another neuron had sent before it reached its recipient.

The "interecepting" inhibitory neuron accomplished this by releasing inhibitory neurotranmitter not onto the recipient neuron, but by releasing the inhibitory chemical onto the sender, right at the very end, just as the signal is about to release the sender's neurotransmitter.

Of course, as with all interceptions, timing matters. If the interceptor released its inhibitory signal too early (shown in A) or too late, there was little inhibition. But if the interceptor released its signal a couple of milliseconds before the sender (shown in B), it could almost entirely knock out the signal from the sender to the recipient.

This mechanism of presynaptic inhibition was later found to fairly widespread. It occurs in vertebrates, and in synapses within brains. It wasn't just a quaint little crayfish curiosity.


Atwood HL. 1976. Organization and synaptic physiology of crustacean neuromuscular systems. Progress in Neurobiology 7: 291-391. http://dx.doi.org/10.1016/0301-0082(76)90009-5

Dudel J, Kuffler SW. 1961. Presynaptic inhibition at the crayfish neuromuscular junction. Journal of Physiology 155: 543-562. http://jp.physoc.org/cgi/reprint/155/3/543

06 July 2008

New salvos in the publishing wars

SalvoI've talked a little about open access research publishing here, so wanted to point out the recent sniping across no man's land on the subject. The opening salvo was fired by Nature. I haven't read the article, because it's password protected and I don't want to pay the 8 bucks, so you can guess where Nature stands on this issue. The tone of the article seems to have caught many off guard as quite nasty.

The Nature article does have reader comments below it, if you have some time. There's quite a few.

You can find a compilation of reactions to the Nature article at A Blog Around the Clock, which includes this pithy comment:

...PLoS has no intention to in any official way acknowledge the existence of this article (according to the old blogospheric rule "Do Not Feed The Trolls")(.)

There's also a lengthy post over at The Questionable Authority on the subject.

My only comment for now is to repeat the mantra that led me to start this website.

Ideas that spread, win.

Additional: Greg Laden has compiled things that Nature has published about PLoS over the years here.

01 July 2008

Pic of the moment: 1 July 2008

I haven't made the T-shirt yet, but here's some desktop wallpaper in the meantime...

Amazon crayfish
With all due apologies to Henry Jones, Jr.

24 June 2008

Crayfish eating monkeys!

Sea MonkeysAs I've mentioned previously, I've been finding a limiting factor in rearing Marmorkrebs to be getting them from early juvenile to the late juvenile stage. Now, I read in a new paper by González and colleagues that this is a fairly typical problem for aquacultured crayfish. They write:

The main constrains to intensified astacid culture are the unpredictable and usually poor survival and growth rates of juveniles during the first months of independent life, when feeding is a decisive factor(.)

Part of their solution to this problem is not one I probably would have thought of: Artemia.

Artemia, also known as brine shrimp, are tough little crustaceans. Aquarium owners have used them as live food for various tropical fish for decades. Some people have them in aquaria just on their own -- they were sold for years, and are still sold, as "Sea monkeys." The picture shown is one that any comic reader of a particular age will recognize. (And yes, I'm of that particular age).

I hadn't considered Artemia as crayfish food for a couple of reasons. First, I associate them more with salt water, as they usually live in inland salty lakes, rather than fresh. More to the point, Artemia tend to swim around in the water column, whereas crayfish -- even juveniles -- are more confined to the bottom. I would have thought it tricky for crayfish to catch the little Artemia.

Still, I am not one to argue with success. The González and colleagues paper reports that supplementing crayfish foodstuffs with Artemia nauplii significantly improved survival and growth. Now, growing Artemia is not that big of a deal, but it does require a bit of effort. So this paper looks at whether using a mix of live Artemia plus artificial diets based on Artemia can accomplish the same thing as using live Artemia alone.

The short answer is, "Yes."

The two feeds testing in the paper were ArteMac-3 and Proton #2. Crayfish fed on these and some live Artemia did just as well as those that fed on the live Artemia. I plan on looking into both of these soon, but in the meantime, I'm going to rear up some Artemia for the next batch of juvenile Marmorkrebs.


González A, Celada JD, González R, García V, Carral JM, Sáez-Royuela M. 2008. Artemia nauplii and two commercial replacements as dietary supplement for juvenile signal crayfish, Pacifastacus leniusculus (Astacidae), from the onset of exogenous feeding under controlled conditions. Aquaculture: In press. http://dx.doi.org/10.1016/j.aquaculture.2008.06.015

19 June 2008


As I mentioned, my new animal housing arrived recently. Putting it together took a while, but was reasonably straightforward. The biggest task was just sorting all the many boxes and keep them organized.

The main rack is taller than I am, and I'm not short. I'm probably going to have to get another footstool for my students.

All the boxes concerned with the mechanical and electronic parts of the system: sump, pumps, sterilizers, and so on.

Boxes containing the actual tanks the animals will live in, some lids, and a bit of overflow drainpipes.

Two years worth of supplies. Hopefully, there will be more money in two years...

"And if you order now, we'll even throw in this handy toolkit with everything you need to assemble your new animal care system and keep it running! Now how much would you pay?"

My REU student Stephanie surveying the nearly complete critter condo. Starting in July, Stephanie will be taking up Marmorkrebs research for about a year. This picture is "nearly complete" because the company neglected to send one needed component: screens to keep the animals from getting out of the tanks through the outflow of each tank. They're apparently in the process of getting a new manufacturer to make that particular part, but it should be here soon.

18 June 2008

Pic of the Moment: 18 June 2008

This image summarizes the scientific literature about Marmorkrebs in a graphic format.

This image was built by taking the text of all the abstracts from this blog and posting them into a fascinating new web program called Wordle. It generates the image with more frequently appearing words in the text appearing larger.

If I was really ambitious, I would have removed some of the Blogger text (which is why things like my name and "Posted" pop up relatively large). But I'm not that ambitious right now.

13 June 2008

Some assembly required

A guy goes away for a couple of days to a meeting, and comes back his lab to find...

That's right, there's no boxes better than NSF-funded boxes.

Of course, the boxes are not the important bit. The important bit is the new animal care system contained within, which will house a significantly expanded Marmorkrebs breeding and research colony. I had been expecting this for some time. It was actually on campus in Central Receiving many weeks ago, but it was delivered until yesterday (when I was gone) due to an initial error in ordering.*

Just for the heck of it, I'll be posting pictures as this goes in.

Now, where did I put that screwdriver...?

* Note to up and comers starting research labs: Ordering systems at universities are needlessly complex. You will make mistakes. Try to be nice to people in purchasing so they will be inclined to forgive you when you make mistakes.)

Vogt, 2008

Vogt G. 2008. Investigation of hatching and early post-embryonic life of freshwater crayfish by in vitro culture, behavioral analysis, and light and electron microscopy. Journal of Morphology 269(7): 790-811. http://dx.doi.org/10.1002/jmor.10622


The late embryonic and early post-embryonic life period of freshwater crayfish, which is the main time period of organogenesis, is poorly investigated because of the protective brooding behavior of crayfish mothers. A combination of in vitro culture, behavioral observations, and microscopic investigations of organs involved in hatching, attachment, exploration of the environment, and searching and processing of food yielded deeper insights in this important period of life. Experiments were performed with the robust parthenogenetic marbled crayfish. The following results were obtained: (1) Marbled crayfish can be raised in simple in vitro systems from 80% embryonic development to juvenile Stage 4 with up to 100% survival; (2) Hatching is prepared by chemical weakening of the egg shell and completed by levering actions of the hatchling’s appendages; (3) The telson thread, a safety line that keeps the hatchling secured to the mother, is formed by secretions from the telson and the detaching inner layer of the egg case; (4) Molting Stage-1 juveniles are secured by an anal thread that results from delayed molting of the hindgut; (5) Active attachment of the hatchlings to the maternal pleopods with their 1st pereiopods is achieved by an innate fixed action pattern; (6) In vitro, juveniles are motile from Stage 2 despite incomplete development of their balance controlling statocysts. Movement pattern and social behavior vary greatly among individuals; and (7) Feeding starts in Stage 3, when the mouthparts and the gastric mill are fully developed. Onset of feeding is innate and does not require maternal contributions. In vitro culture of the isogenic marbled crayfish is recommended for broader use in research because it enables not only time and stage-specific sampling but also precisely timed experimental manipulations.

Keywords: marbled crayfish • in vitro culture • hatching • development • digestion • sense organs