31 March 2009

Market organisms?

Science magazine cover for 27 March 2009Science magazine last week featured a book review of the first volume of Emerging Model Organisms. Since this is what I hope Marmorkrebs to be, I looked at this with great interest. And luckily, author Jonathan Slack did make some instructive comments on what makes for a successful model organism.

A model organism must exemplify some key general biological problem that can be solved relatively easily with it and that will turn out to have the same answer for more important but experimentally less tractable organisms, namely human beings or economically important domestic animals and crop plants.

Because I’m a neurobiologist, my opinion may be skewed, but it seems to me that crayfish serve well for general biological problems related to nervous system organization and function, as I hope I show my irregular series, “Great Moments in Crayfish Research.” So, in a sense, Marmorkrebs is not entirely a new model organism, but a variation that can take advantage of new questions (e.g., evo-devo) and methodologies (e.g., transgenics). Marmorkrebs do also serve as a model for “economically important animals,” namely other large decapod crustaceans like lobsters and crayfish, whose rearing is less convenient.

The book's protocols reveal that not all the aspirant models are capable of being bred in the lab—something I would consider a basic requirement.

And that’s a point in Marmorkrebs favour, though I’ll be the first to admit that the fairly long generation time and a few related concerns are issues.

For those who manage science funding, the book should pose the question: How many model organisms do we need? That issue is all the more urgent because there is a second volume of this series looming, so there will soon be another 20 or so organisms wanting to get their snouts, tentacles, probosci, or roots into the trough. We practitioners of academic life sciences feel we require a doubling of total expenditure about every five years to remain reasonably comfortable. Funding bodies have found this a difficult target to meet, and it will become even harder with so many more model organisms to feed.

I added the emphasis, because the statement is one that I have never seen before. It’s not clear to me if he’s talking about individual researchers, a research lab, a research field, or something else. But I’ll take a stab at replying to Slack’s rhetorical question with one of my own.

How many more Drosophila researchers do we need? Or mouse? Or C. elegans? Or E. coli?

Now, I am not criticizing anyone who works on those organisms. I know a lot of those people, and I like a lot of those people, and appreciate the science that they do. But the recruitment of researchers to existing model organisms resembles what Jorge Cham called a “Profzi scheme,” where more and more people are working on fewer and fewer organisms.

Perhaps a lesson can be taken from ecology rather than economy. In ecology, it’s often the case that there are advantages to being rare.


Slack JMW. 2009. Emerging market organisms. Science 323(5922): 1674-1675. doi: 10.1126/science.1171948

Various authors. 2009. Emerging Model Organisms, A Laboratory Manual, Volume 1.
Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY. ISBN 9780879698263. ISBN 9780879698720. http://cshprotocols.cshlp.org/emo/

30 March 2009

Perspective on a problem

Madagascar has been mentioned several times in this blog because Marmorkrebs have been introduced into the wild there. 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.

Sadly, there political situation is spilling over into research and conservation issues. A suite of conservation groups have issued a statement that describes the current conservation situation:

Open and organized plundering, sometimes using firearms, of precious wood from several natural forests, including national parks such as Marojejy and Masoala, which have been declared World Heritage Sites.

Intensified smuggling of wild species, especially reptiles such as tortoises, to the national and international markets.

Proliferation, due to the current impunity, of destructive practices such as illegal mining and slash-and-burn agriculture within protected areas and environmentally sensitive areas.

26 March 2009

Great moments in crayfish research: Serotonin, octopamine, and social status

The paper is usually remembered as using lobsters, probably because many of the later papers springing from it used lobsters. But there were crayfish in there too, and I have the photographic evidence to prove it.

Aggressive and subordinate looking crayfish
These two pictures show good old Louisiana red swamp crayfish, Procambarus clarkii, the lab rat of the crustacean world. The animal on the left is in a pose that would normally be associated with an aggressive animal, one gearing up for a fight. The animal on the right is in a pose that would normally be associated with, “Please don’t kill me.”

Crayfish fighting has been consistently studied for over half a century (Bovbjerg 1956 is a seminal paper), and are a fairly well used model for aggression. There are many reasons for this, but one is that crayfish will fight early, often, and for no reason. They fight when they are small, so the behaviour is completely “hard wired.” They fight if there is no food, shelter, or mating opportunities at stake. Fighting is just something they do.

Now, we normally think of fighting as a fairly complicated behaviour. You have to assess your opponent. Make tactical decisions to continue on the fight or leave. Thus, you would think that finding a way “into the system” would be quite tricky.

That’s where the experiment pictured above comes in. The crayfish shown are not animals that are in a fight. instead, they have been injected with the neuroactive chemicals. The individual on the left has been injected with serotonin (also known as 5-hydroxytryptamine, or 5-HT). The individual on the right has been injected with octopamine.

What looked to be a potentially intractable problem involving many neurons was simplified and made tractable at a stroke. It now appeared that crayfish – and other similar decapod crustaceans – had a couple of fairly simple “master dials” on their behavioural control panel relating to aggression and social status. And those fairly simple dials were things that experimenters could use to fiddle with the system. Finding out that simple injection of these chemicals mimicked some important aspects of fighting behaviour paved the way for many later papers.


Bovbjerg RV. 1956. Some factors affecting aggressive behaviour in crayfish. Physiological Zoology 29: 127–136.

Livingstone MS, Harris-Warrick RM, Kravitz EA. 1980. Serotonin and octopamine produce opposite postures in lobsters. Science 208(4439): 76-79. doi: 10.1126/science.208.4439.76

17 March 2009

Losing sex

A forthcoming article in Trends in Ecology & Evolution (a.k.a. TREE) looks at the problem of detecting whether an organism reproduces sexually or asexually. This might seem to be a trivial problem, but it isn’t. For one, many organisms are poorly studied. And we are starting to discover that some organisms can switch between sexual and asexual reproduction.

Komodo dragons provide a good example of the latter. Because they are “charismatic megafauna” (they’re the biggest lizards in the world, and we love biggest and smallest things), there’s no shortage of people looking at them and maintaining them in zoos. But it was only a few years ago that it was found that females could also reproduce asexually (Watts et al. 2006).

In the TREE article, Schurko and collegues list four ways that an asexually reproducing species, like Marmorkrebs, can originate.

  • Hybridization: Many asexual species appear to be the result of interbreeding between two different sexual species. Just by virtue of how many parthenogens are thought to be hybrids, this might be the number one contender for the origin of Marmorkrebs.

  • Spontaneously: You get an unlucky (or lucky, depending on your point of view) genetic change, either through a mutation or anomalous gamete formation.

  • Infectious: Some bacteria, most famously Wolbachia, can influence the reproduction of hosts they infect, and can dramatically skew sex ratios.

  • Contagious: I’m not 100% clear how this one works, but involves the spread of “asexual genes.” The reference given is a crustacean case, Daphnia pulex (Innes & Hebert 1988).

It’s a completely open question at this point which of these four possibilities led to the formation of Marmorkrebs. But knowing the range of possibilities is important in figuring out ways of testing those hypotheses.


Innes DJ, Hebert PDN. 1988. The origin and genetic basis of obligate parthenogenesis in Daphnia pulex. Evolution 42(5): 1024-1035

Schurko AM, Neiman M, Logsdon JM Jr. 2009. Signs of sex: what we know and how we know it. Trends in Ecology & Evolution: in press. http://dx.doi.org/10.1016/j.tree.2008.11.010

Watts PC, Buley KR, Sanderson S, Boardman W, Ciofi C, Gibson R. 2006. Parthenogenesis in Komodo dragons. Nature 444(7122): 1021-1022. http://dx.doi.org/10.1038/4441021a

16 March 2009

Marmorkrebs on the road: Texas Academy of Science 2009

Texas Academy of Science meeting 2009
UTPA REU students. L to R: Ammie Ortiz, Amery Yang, Stephanie Castellanos, Ashley Longoria, Stephanie Jimenez, Jess Valdez.

Stephanie Jimenez, my REU student, was in Junction, Texas, recently for the annual Texas Academy of Science meeting on March 6th. She had a new talk to give, quite different from her SICB poster. It was titled, “Peaceful parthenogens? Social behavior of Marmorkrebs, a parthenogenetic crayfish.”

If you’re one of the individuals Stephanie met at TAS, welcome!

10 March 2009

Pic of the moment: 10 March 2009

Marmorkrebs interacting
Two Marmorkrebs interacting. The one on the right (the blur) has had enough, and is tailflipping away.

Crayfish fighting has been extensively and intensively studied. I may write about it in some future blog posts.

09 March 2009

Open Lab 2008 hits town

I got my printed and bound copy of The Open Laboratory 2008 blogging anthology in the mail today. Though I say it myself being a contributor, it looks very nice. The only qualm I have is that the image quality is a little patchy, but being restricted to black and white makes conversion from the colour we’ve come to know on the web understandably problematic. I’m willing to bet that most people didn’t pick graphics for their blog posts with the idea of them being reprinted in a black and white anthology at the end of the year.

05 March 2009

Marmorkrebs.org redesign

Here's a look at the new design for the Marmorkrebs.org home page.

Marmorkrebs.org home page
What do you think?

03 March 2009

A matter of patience

This graph shows one of the biggest obstacles facing researchers who want to work with Marmorkrebs and, to a lesser degree, a lot of other crustaceans. It’s a graph comparing generation time of common research animals. How long does it take for an organism to grow and reproduce? Clearly, most modern model organisms have been selected in part for short generation times. Live fast, die young.

While I don't pretend that this graph is exhaustive, the only datum on this graph longer than Marmorkrebs deserves comment. Xenopus laevis has been used for research for a long time, but even it is competing with a related species, Xenopus tropicalis, which has a much shorter generation time.

Most decapod crustacean researchers have dealt with this problem in a straightforward way: they only study adults, and they don’t rear animals in the lab. Instead, crayfish, lobsters, and crabs are collected from wild populations or from commercial suppliers. But this seems rather too limiting on research that can be done.

There may be a silver lining for Marmorkrebs, however. Generation time may be long, but there are two mitigating factors. First, crayfish lifespan is relatively long. Second, once a Marmorkrebs hits reproductive age, it can generate new batches of eggs in a couple of months. I'm not sure how many times fruit flies or C. elegans can generate offspring in their brief lives, but the number of reproductive opportunities per animal may be lower for some of the fast-living animals.

Furthermore, short life span has traditionally been a major advantage for genetic research, where breeding used to be necessary to examine the traits of interest. You had to have animals reproduce to see the patterns of inheritance Now that there are many more genetic tools available, straight ahead breeding experiments may be a little less common, less of a staple experiment, than they used to be. Instead of trying to breed a mouse with certain characteristics, you can use directed genetic tools to affect the relevant genes.

Given that Marmorkrebs reproduce asexually, those directed tools might be able to take the place of the traditional breeding experiments. Thus, it might not matter that Marmorkrebs live slow and die old.

02 March 2009


The latest Circus of the Spineless, #36, is now out, this month hosted by Invertebrate Diaries. Support invert blogging!

Open Laboaratory 2008 now available

The Open Laboratory 2008 coverThe third annual science blogging anthology is now available at Lulu. When you get your copy, you’ll want to turn to page 86.

Additional: In the spirit of openness, I will remind everyone that you can read the book for free by following the links here. Inconvenient compared to a nice, unified, cleanly typeset, high-resolution, portable compilation, if you ask me.

There is, however, another reason to buy the compilation (which is available for immediate download as a PDF as well as a traditional paperback format). Bora writes:

In a few weeks, the book will also be available at other online retailers, e.g., Amazon.com, but we prefer that you buy from Lulu.com as the proceeds will go towards organizing ScienceOnline‘10 next January.

ScienceOnline is a science blogging conference. Next year’s will be the fourth such event. Of course, people blogged about it at length, but a very brief intro to last year’s is here.