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.