26 March 2008


NSF logoI 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.

20 March 2008

Pic of the Moment: 20 March 2008

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

11 March 2008

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.

03 March 2008

Rieger and Harschz, 2008

Tissue and Cell coverRieger V & Harzsch S. 2008. Embryonic development of the histaminergic system in the ventral nerve cord of the Marbled Crayfish (Marmorkrebs). Tissue and Cell 40(2): 113-126.


The embryonic development of neurotransmitter systems in crustaceans so far is poorly understood. Therefore, in the current study we monitored the ontogeny of histamine-immunoreactive neurons in the ventral nerve cord of the Marbled Crayfish, an emerging crustacean model system for developmental studies. The first histaminergic neurons arise around 60% of embryonic development, well after the primordial axonal scaffold of the ventral nerve cord has been established. This suggests that histaminergic neurons do not serve as pioneer neurons but that their axons follow well established axonal tracts. The developmental sequence of the different types of histaminergic neurons is charted in this study. The analysis of the histaminergic structures is also extended into adult specimens, showing a persistence of embryonic histaminergic neurons into adulthood. Our data are compared to the pattern of histaminergic neurons in other crustaceans and discussed with regard to our knowledge on other aspects of neurogenesis in Crustacea. Furthermore, the possible role of histaminergic neurons as characters in evolutionary considerations is evaluated.

Keywords: Arthropoda • neurophylogeny • development • neurotransmitter • neurogenesis • histamine