Braband and colleagues, 2006

Braband A, Kawai T, Scholtz G. 2006. The phylogenetic position of the East Asian freshwater crayfish Cambaroides within the Northern Hemisphere Astacoidea (Crustacea, Decapoda, Astacida) based on molecular data. Journal of Zoological Systematics and Evolutionary Research 44(1): 17-24. http://dx.doi.org/10.1111/j.1439-0469.2005.00338.x

Abstract

The phylogenetic position of the four East Asian freshwater crayfish species of the genus Cambaroides is not settled. Morphological phylogenetic analyses suggest close affinities of Cambaroides with North American Cambaridae. This view is based mainly on characters of the male and female reproductive organs. In contrast, the only molecular phylogenetic analysis so far available leaves the phylogenetic position of Cambaroides unresolved. The question of whether Cambaroides is monophyletic or paraphyletic has so far been neither addressed morphologically nor with molecular data sets. Here we present the first comprehensive phylogenetic analysis of all four currently described species of Cambaroides in the framework of Northern Hemisphere freshwater crayfish (Astacoidea) relationships based on partial sequences of two mitochondrial genes (CO1 and 12S rRNA). Despite some evidence in favour of a monophyletic Cambaroides more data is needed to resolve this question. Our analyses
suggest a close relationship of the North American Cambaridae and the European Astacidae, leaving the Asian Cambaroides basal to them. If these results hold true the similar reproductive organs of Cambaroides and American Cambaridae must be either homoplastic or ancestral for Northern Hemisphere Astacoidea.

Keywords: mitochondrial genes • evolution • reproductive organs • Astacoidea • arthropods

Keeping them alive

The biggest problem with rearing Marmorkrebs is that the high mortality in the early stages -- before individuals get to about a centimeter or so long. Getting embryos is not a problem. Getting hatchlings is not a problem. Nurturing them through to a moderate sized juvenile is the problem.

I don't know if there is anything that can be done about that, however. Most crustaceans do have a reproductive strategy emphasizing quantity of offspring rather than quality.

This suggests that at least initially, developmental research will probably proceed faster than other types of research that revolves around adult organisms.

Marmorkrebs labs

Over on the left side of this blog, I've added a new list of links (you'll have to scroll down some distance) of labs that I know are working with Marmorkrebs. I apologize in advance that the list is incomplete. Please email me if you would like to have your lab listed.

Great moments in crayfish research: The model organism

The great Victorian biologist, Thomas Henry Huxley, is famed for his defense of the concept of natural selection, for first proposing a relationship between birds and dinosaurs, and many other achievements. Less well known among general biologists was his book titled The Crayfish: An Introduction to the Study of Zoology.

In inimitable Victoria prose, he prefaced his book by saying:

I have desired, in fact, to show how the careful study of one of the commonest and most insignificant of animals, leads us, step by step, from every-day knowledge to the widest generalizations and the most difficult problems of zoology; and, indeed, of biological science in general.

It is for this reason that I have termed the book an “Introduction to Zoology.” For, whoever will follow its pages, crayfish in hand, and will try to verify for himself the statements which it contains, will find himself brought face to face with all the great zoological questions which excite so lively an interest at the present day; he will understand the method by which alone we can hope to attain to satisfactory answers of these questions; and, finally, he will appreciate the justice of Diderot's remark, “Il faut être profond dans l'art on dans la science pour en bien posséder les éléments.”

Ah, the old “throw in a quote in another language without a translation to show how smart you are” trick.

This may be one of the earliest explicit justifications for using a single organisms to study a host of biological problems. Those single organisms are known today as model organisms. The 20^th century was when the concept of model organisms really rolled into force, perhaps starting with fruit flies (Drosophila melanogaster). Certainly, by the mid-century scientists had taken Huxley's lengthy justification and traded them for bon mots like this one from Jacques Monod, “What is true for E. coli is also true for the elephant.”

So, arguably, crayfish contributed to the model organism concept. From time to time, I'll be highlighting basic biological discoveries that were made by studying crayfish. Which, I hope, Marmorkrebs will be adding to as more labs begin to work with this organism.

Here's a link to an HTML version of Huxley's text, and here's the Google books version.

Additional (23 February 2009): Monod's quote is preceded by a similar one by Albert Kluyver: “From the elephant to butyric acid bacterium—it is all the same!”

Funded!

I am pleased to note that the National Science Foundation has awarded a grant for Marmorkrebs research and spreading this animal as a model organism in North America.

I'm also pleased to note that it's been awarded to me.

I'm looking froward to being able to provide more resources to fellow researchers, and this grant will significantly help those efforts.

Pic of the Moment: 20 March 2008

An adult with very early stage embryos under her abdomen (judging from how black the eggs are).

How Marmorkrebs can make the world a better place

One of the longest-running (and least productive) arguments in biology is “nature versus nurture.” The pendulum has swung back and forth many times, but with the research success of genome sequencing for many species (not the least of which has been humans), there is definitely a tendency to give a lot of weight – often unwarranted – to genetics.

This New York Times article talks in some detail about how much emphasis DNA gets in explaining “what we are.”

“I’ve spent the last 10 years of my life researching how much genetic variability there is between populations,” said Dr. David Altshuler, director of the Program in Medical and Population Genetics at the Broad Institute in Cambridge, Mass. “But living in America, it is so clear that the economic and social and educational differences have so much more influence than genes. People just somehow fixate on genetics, even if the influence is very small.”

Marmorkrebs show very beautifully that DNA is not destiny.

Despite that Marmorkrebs are all genetically identical (as Martin and colleagues showed), there is substantial variation across individuals (as Vogt and colleagues showed).

The picture in this entry shows two juvenile Marmorkrebs. Believe it or not, they are about the same age. They have been kept for a couple of months in the same environment, same food, same lighting conditions, and so on. Yet one is about 60% longer than the other, which probably means it’s about 400% greater in mass. (When length doubles, volume goes up by a factor of eight.)

It’s been really fascinating to watch them grow, knowing they are all the same genetically. In a tank of ten animals, the big individual in the picture noticeably pulled away from all the others in growth, one was noticeably smaller than its peers, and the other eight were much more similar in size.

It’s one thing to know intellectually that your genes are only part of what determines how you end up. It’s something entirely different, and more powerful, to see it unfolding right in front of your eyes. Strong, obvious cases like this could do much to give people a more balanced view of the “genes as destiny” argument, which has been used to justify some really horrible treatment of people over the years.