Friend of the blogGünter Vogt has a write-up for non-specialists about Marmorkrebs at the Atlas of Science.
A new feature by Jordana Cepelewicz in Quanta Magazine starts off using marbled crayfish to make a point about variation:In the 1990s, an army of clones invaded Germany. Within a decade, they had spread to Italy, Croatia, Slovakia, Hungary, Sweden, France, Japan and Madagascar — wreaking havoc in rivers and lakes, rice paddies and swamps; in waters warm and cold, acidic and basic. The culprits: six-inch-long, lobster-like creatures called marbled crayfish. ...Marmorkrebs are not the point of the article, but it’s nice to see them so prominent featured. It’s a nice example of how marbled crayfish can be used as a model for general biological problems.
New research on crayfish and scores of other organisms is revealing an important role for a third, often-overlooked source of variation and diversity — a surprising foundation for what makes us unique that begins in the first days of an embryo’s development: random, intrinsic noise.
A doctoral position to study “Marbled crayfish as a model organism” is available! The position is in Czechia with Antonín Kouba. More information about the position are here.
The International Association for Astacology meeting was recently held in Spain, and a nice press release about the two major lines of research on Marmorkrebs: as an unwanted invasive, and as a wanted model organism. I draw similar comparisons in my own chapter.
- This North American species is reshaping ecosystems by killing fish or molluscs on the one hand, and on the other hand, is used for studies related to cancer thanks to their particular genetics.
- Researchers Pavel Kozák and Frank J. Lyko presented studies about this crustacean at the 21st International Symposium of Astacology.
The marble crayfish (Procamborus (sic) fallax) is a curious exotic species, as has been disclosed during the 21st International Symposium of Astacology, which takes place at the Royal Botanical CSIC Garden. Like the strange case of Dr. Jekyll and Mr. Hyde, it shows two sides: a positive, because thanks to their particular genetics, it is used for cancer-related studies; and the other less pleasant, because it is an invasive species that is ravaging different ecosystems.
Researchers Pavel Kozák from the Faculty of Fisheries and Protection of Waters of the University of South Bohemia in the Czech Republic, and Frank J. Lyko, from the Cancer Research Center of Heidelberg in Germany, are working on two projects related to marbled crayfish. They presented their studies on this species from the point of view of ecology and reproduction (Kozák) and genetics (Lyko).
According to the Czech researcher, his project initially focused on the impact of invasive species on native species of crayfish, but as the project continued, this deepened to include the interaction between this invasive species and their impact on other invasive species, such as amphibians or fish.
The researcher Kozák focuses on two significant events. “First, marbled crayfish are destroying fish, molluscs, and macroinvertebrates, and ultimately, it is reshaping the entire ecosystem. Second, this invasive species is more powerful than other larger species, thus refuting the claim that the larger species tend to be more aggressive.”
Meanwhile, the German researcher Frank J. Lyko notes that the genetics of marbled crayfish reproduction, i.e., the females create clones of themselves, “is a model species to implement our work on cancer, since there is only one genome to study, hence its importance for medical science.”
Devastating effects
However, Lyko coincides with his Czech colleague Kozák in the “devastating effects” of marbled crayfish, such as in Madagascar where they have destroyed almost all the habitat where they have been, before making the leap to other countries. The first crayfish in Europe were found in Germany in 1995, and by 2010, it was established in nature, especially Central Europe. In the short term, also has changed the habitat of this area.
The two researchers also agree that, given that its eradication is impossible, citizens of the areas where this species is found be educated to know how easily it reproduces and the consequences of their invasion. They also requested legislation regulating the introduction of new species and greater control of ornamental trade, both in physical stores and the sale online, because it is very easy to get this species for aquariums, and their reproduction is immediate and unlimited.
Finally, for Czech researcher Pavel Kozák, this highlighted the work of the Royal Botanic Garden-CSIC of Madrid, which conducts research related to crayfish plague and supports students doing projects on astacology.
Martin P, Thonagel S, Scholtz G. 2016. The parthenogenetic Marmorkrebs (Malacostraca: Decapoda: Cambaridae) is a triploid organism. Journal of Zoological Systematics and Evolutionary Research 54(1): 13–21. http://dx.doi.org/10.1111/jzs.12114
Günter Vogt, a zoologist at Heidelberg University suggested that the DKFZ scientists take a look at the freshwater marbled crayfish which has now spread worldwide. In Madagascar, it reproduces so quickly that it poses a threat not just ecologically but also economically as the animals destroy rice crops. Marbled crayfish also occur in the lakes of southern Germany as well as in Sweden and Japan and are now even readily available in most aquarium and pet stores.
“As there are only females, I suspected that these crayfish might reproduce by cloning. If so, then these animals should all have identical DNA and the large variety in appearance and behaviour might be based entirely on epigenetic causes.”
Lyko was curious and started looking at these animals in the lab which confirmed the assumption. “We examined the DNA of 4 animals and found that they were completely identical, we did not detect a single genetic difference. The marbled crayfish is indeed a clone - millions of animals derive from a single original specimen.”
In March, five Western Michigan University students won a $15,000 Wege Prize—a national sustainability award—for their aquaponics system.
Instead of buying regular fish food, the team will raise spirulina algae and marbled crayfish—both of which are easy to raise.
Marbled crayfish
This recently-discovered crustacean species reproduces through parthenogenesis, an asexual process in which a single female creates genetically identical clones. As an all-female species, marbled crayfish reproduce exponentially and are less aggressive than other species, which makes them better suited for aquaculture. They are fed spirulina algae and BSFL frass. Being omnivorous scavengers, the crayfish can also process undigested waste as supplemental feed. In this system, they are used as a feed component, but could be raised for human consumption if demand exists.
It might be tricky to keep mangrove rivulus in your typical aquarium. Mangrove rivulus are rather found of jumping out of water – and staying there. 
Mangrove rivulus have an advantage for studying these sorts of short-term physiological changes, as many of them are genetically identical, because they are hermaphrodites - not all that unusual among animals, but that they are self-fertilizing hermaphrodites is a rare and exceptional feature among vertebrates.
Daphnia represents the only ‘model’ organism where we even have a vague idea of the ecology and life-history.
But Daphnia pulex does NOT have a big genome. It’s about 200Mb, slightly larger than Drosophila melanogaster, and about 1/15 the size of the human genome.
Is this “uncertainty hypothesis” right? There is evidence that epigenetic changes, as opposed to genetic mutations or environmental factors, are responsible for a lot of variation in the characteristics of organisms. The marbled crayfish, for instance, shows a surprising variation in coloration, growth, lifespan, behaviour and other traits even when genetically identical animals are reared in identical conditions. And a study last year found substantial epigenetic differences between genetically identical human twins. On the basis of their findings, the researchers speculated that random epigenetic variations are actually “much more important” than environmental factors when it comes to explaining the differences between twins (Nature Genetics, vol 41, p 240).
It’s almost another marbled clone.
They did find new genetic variation that appeared to have cropped up since the animals had been collected for the lab, which they attributed to new mutations. In fact, one gene seemed to be a mutational “hotspot,” mutating several times in different lines.Good idea: A paper in the Journal of Heredity proposes sequencing 10,000 genomes...
The most recent paper concerning Marmorkrebs says:While this manuscript was being prepared, Jones et al. (2008) (sic) published an account of a molecular study identifying crayfish specimens collected in Madagascar as Marmorkrebs.
