13 May 2015

Vogt, 2015

Vogt G. 2015. Stochastic developmental variation, an epigenetic source of phenotypic diversity with far-reaching biological consequences. Journal of Biosciences 40(1): 159-204. http://dx.doi.org/10.1007/s12038-015-9506-8


This article reviews the production of different phenotypes from the same genotype in the same environment by stochastic cellular events, nonlinear mechanisms during patterning and morphogenesis, and probabilistic self-reinforcing circuitries in the adult life. These aspects of phenotypic variation are summarized under the term ‘stochastic developmental variation’ (SDV) in the following. In the past, SDV has been viewed primarily as a nuisance, impairing laboratory experiments, pharmaceutical testing, and true-to-type breeding. This article also emphasizes the positive biological effects of SDV and discusses implications for genotype-to-phenotype mapping, biological individuation, ecology, evolution, and applied biology. There is strong evidence from experiments with genetically identical organisms performed in narrowly standardized laboratory set-ups that SDV is a source of phenotypic variation in its own right aside from genetic variation and environmental variation. It is obviously mediated by molecular and higher-order epigenetic mechanisms. Comparison of SDV in animals, plants, fungi, protists, bacteria, archaeans, and viruses suggests that it is a ubiquitous and phylogenetically old phenomenon. In animals, it is usually smallest for morphometric traits and highest for life history traits and behaviour. SDV is thought to contribute to phenotypic diversity in all populations but is particularly relevant for asexually reproducing and genetically impoverished populations, where it generates individuality despite genetic uniformity. In each generation, SDV produces a range of phenotypes around a well-adapted target phenotype, which is interpreted as a bet-hedging strategy to cope with the unpredictability of dynamic environments. At least some manifestations of SDV are heritable, adaptable, selectable, and evolvable, and therefore, SDV may be seen as a hitherto overlooked evolution factor. SDV is also relevant for husbandry, agriculture, and medicine because most pathogens are asexuals that exploit this third source of phenotypic variation to modify infectivity and resistance to antibiotics. Since SDV affects all types of organisms and almost all aspects of life, it urgently requires more intense research and a better integration into biological thinking.

Keywords: clonal organisms • development • ecology • epigenetics • evolution • genotype-to-phenotype mapping • individuality • infectivity and resistance • phenotypic variation • stochasticity

Mrugała and colleagues

Mrugała A, Kozubíková-Balcarová E, Chucholl C, Cabanillas Resino S, Viljamaa-Dirks S, Vukić J, Petrusek A. 2015. Trade of ornamental crayfish in Europe as a possible introduction pathway for important crustacean diseases: crayfish plague and white spot syndrome. Biological Invasions 17(5): 1313-1326. http://dx.doi.org/10.1007/s10530-014-0795-x


Rapidly growing trade of ornamental animals may represent an entry pathway for emerging pathogens; this may concern freshwater crayfish that are increasingly popular pets. Infected crayfish and contaminated water from aquaria may be released to open waters, thus endangering native crustacean fauna. We tested whether various non-European crayfish species available in the pet trade in Germany and the Czech Republic are carriers of two significant crustacean pathogens, the crayfish plague agent Aphanomyces astaci and the white spot syndrome virus (WSSV). The former infects primarily freshwater crayfish (causing substantial losses in native European species), the latter is particularly known for economic losses in shrimp aquacultures. We screened 242 individuals of 19 North American and Australasian crayfish taxa (the identity of which was validated by DNA barcoding) for these pathogens, using molecular methods recommended by the World Organisation for Animal Health. A. astaci DNA was detected in eight American and one Australian crayfish species, comprising in total 27 % of screened batches. Furthermore, viability of A. astaci was confirmed by its isolation to axenic cultures from three host taxa, including the parthenogenetic invader Marmorkrebs (Procambarus fallax f. virginalis). In contrast, WSSV was only confirmed in three individuals of Australian Cherax quadricarinatus. Despite modest prevalence of detected infections, our results demonstrate the potential of disease entry and spread through this pathway, and should be considered if any trade regulations are imposed. Our study highlights the need for screening for pathogens in the ornamental trade as one of the steps to prevent the transmission of emerging diseases to wildlife.

Keywords: aquarium trade • exotic pathogens • Aphanomyces astaci • white spot syndrome virus • Marmorkrebs • DNA barcoding

14 April 2015


Last month, I finally manage to watch a show for which I’d heard many positive things:Orphan Black.

If you have not see it, I highly recommend this show. I’m writing about it here on this blog because the show is about genetically identical females – much like Marmorkrebs.

There are so many striking things about this show. The performance of lead actress Tatiana Maslany is astonishing. But as a biologist, I was struck by how sophisticated the portrayal of the science is. The show is fortunate to have a very good scientific consultant, Cosima Herter, who shares a first name with one of the lead characters.

The show’s take on clones stands in a stark contrast to many other depictions of clones in pop culture. Whereas most stories emphasize the similarities of the clones, Orphan Black runs the opposite way, and hammers away at the differences of the women in the show. The individual characterization is so complete and so well thought through and so consistent that you continually forget that it is all performed by one person. (Two if you count the body double Kathryn Alexandre).

It reminded me of my post from several years ago about how one of the great things about Marmorkrebs was that you could see the differences between sisters that started with the same identical genetic materials.

As I thought about it, another recent show also emphasized that clones were individuals: Star Wars: The Clone Wars series. As the series progressed, it gave the clone troopers names. Different haircuts. Different insignia. In short, the clones stopped being interchangeable cannon fodder and became distinct characters.

Do these shows reflect a larger cultural shift in our thinking about how genetics affects our identities? Too soon to tell, but I find the different portrayals of genetically identical individuals fascinating.

A new season of Orphan Black starts this weekend. And I can’t wait.

Related posts

How Marmorkrebs can make the world a better place

External links

Meet the real Cosima, Orphan Black's science consultant: The Crazy Science Of Orphan Black

The real life science behind Orphan Black
The many faces of Tatiana Maslany
Meet The Woman (Besides Tatiana Maslany) Who Plays Every Single "Orphan Black" Clone

07 April 2015

Marmorkrebs: the Early Years

Chris Lukhaup was one of the co-authors of the paper that introduced Marmorkrebs to the scientific world (Scholtz et al. 2003). He has been active in describing many new species of crustaceans, often emerging from the pet trade (for example, Lukhaup & Pekny 2006, 2008). He takes stunning pictures. He recently contacted me with this bit of history about Marmorkrebs, which I share with his permission (lightly edited):

When I contacted Jay Huner in Louisiana back in 2000 to tell him that I believe that the Marmorkrebs is a parthenogenetic species, he wrote me back and told me that this is impossible! I sent him some animals to check and he wrote me back that this was Procambarus clarkii. ;-) Also he told me that I need to look better because there have to be males and I should learn the difference between males and females.

In 2002, I had my first articles in some aquarium magazines describing the animal and warning already. I wrote an article and offered $3000 for a person bringing me a male Marmorkrebs... this was published in several magazines but nothing happened. Then I went to the USA myself to collect, and I was pretty sure that the Marmorkrebs was very close to Procambarus fallax. I send some animals to Berlin and they approved it. So this is the story of the Marmorkrebs from my side.

Thank you for providing that bit of history!


Lukhaup C, Pekny R. 2006. Cherax (Cherax) holthuisi, a new species of crayfish (Crustacea: Decapoda: Parastacidae) from the centre of the Vogelkop Peninsula in Irian Jaya (West New Guinea), Indonesia. Zoologische Mededelingen 80(1): 101-107. http://www.repository.naturalis.nl/document/41228

Lukhaup C, Pekny R. 2008. Cherax (Astaconephrops) boesemani, a new species of crayfish (Crustacea: Decapoda: Parastacidae) from the centre of the Vogelkop Peninsula in Irian Jaya (West New Guinea), Indonesia. Zoologische Mededelingen 82: 331-340. http://www.zoologischemededelingen.nl/82/nr02/a33

Scholtz G, Braband A, Tolley L, Reimann A, Mittmann B, Lukhaup C, Steuerwald F, Vogt G. 2003. Parthenogenesis in an outsider crayfish. Nature 421(6925): 806-806. http://dx.doi.org/10.1038/421806a

External links

Chris Lukhaup on Facebook
Chris Lukhaup’s pictures on Flickr

15 March 2015

Jirikowski and colleagues, 2015

Jirikowski G, Wolff C, Richter S. 2015. Evolution of eumalacostracan development--new insights into loss and reacquisition of larval stages revealed by heterochrony analysis. EvoDevo 6(1): 4. http://dx.doi.org/10.1186/2041-9139-6-4



Within Malacostraca (Crustacea), direct development and development through diverse forms of larvae are found. Recent investigations suggest that larva-related developmental features have undergone heterochronic evolution in Malacostraca. In the light of current phylogenetic hypotheses, the free-swimming nauplius larva was lost in the lineage leading to Malacostraca and evolved convergently in the malacostracan groups Dendrobranchiata and Euphausiacea. Here we reconstruct the evolutionary history of eumalacostracan (Malacostraca without Phyllocarida) development with regard to early appendage morphogenesis, muscle and central nervous system development, and determine the heterochronic transformations involved in changes of ontogenetic mode.


Timing of 33 developmental events from the different tissues was analyzed for six eumalacostracan species (material for Euphausiacea was not available) and one outgroup, using a modified version of Parsimov-based genetic inference (PGi). Our results confirm previous suggestions that the event sequence of nauplius larva development is partly retained in embryogenesis of those species which do not develop such a larva. The ontogenetic mode involving a nauplius larva was likely replaced by direct development in the malacostracan stem lineage. Secondary evolution of the nauplius larva of Dendrobranchiata from this ancestral condition, involved only a very small number of heterochronies, despite the drastic change of life history. In the lineage leading to Peracarida, timing patterns of nauplius-related development were lost. Throughout eumalacostracan evolution, events related to epidermal and neural tissue development were clearly less affected by heterochrony than events related to muscle development.


Weak integration between mesodermal and ectodermal development may have allowed timing in muscle formation to be altered independently of ectodermal development. We conclude that heterochrony in muscle development played a crucial role in evolutionary loss and secondary evolution of a nauplius larva in Malacostraca.

Keywords: None provided.

25 February 2015

Faulkes, 2015

Faulkes Z. 2015. A bomb set to drop: parthenogenetic Marmorkrebs for sale in Ireland, a European location without non-indigenous crayfish. Management of Biological Invasions 6(1): 111-114. http://dx.doi.org/10.3391/mbi.2015.6.1.09


Ireland is one of the few locations in Europe where non-indigenous North American crayfish species have not been introduced, and is a refuge for endangered white-clawed crayfish, Austropotamobius pallipes (Lereboullet, 1858). The parthenogenetic crayfish species Marmorkrebs, Procambarus fallax f. virginalis (Hagen, 1870), is sold in the pet trade in Ireland within the recorded range of A. pallipes. Marmorkrebs risk being introduced into Irish waters, where they could threaten A. pallipes populations, particularly as a vector for crayfish plague.

Keywords: Marmorkrebs • Procambarus fallax f. virginalisAustropotamobius pallipes • pet trade • Ireland • non-indigenous crayfish species

05 February 2015

The Crustacean Society / International Association of Astacology meeting in Australia, 2015

Oooh, this conference is like a superhero team-up!

Abstract submission is open for a joint meeting of The Crustacean Society (TCS) and the International Association of Astacology. They are looking for presentations from all fields of crustacean research worldwide and invite themed sessions and symposia.

Symposia suggestions should be on the symposium proposal form, and submitted by 14 March 2015.

Abstracts are to be according to the format outlined abstracts page of the conference web site, using the template. People are invited to submit abstracts on any aspect of crustacean research. Abstracts sunbmission deadline is 27 March 2015, and people will be notified of acceptance by 12 April 2015.

The meeting will be held at the Australian Museum. This museum, established in 1827, is the oldest museum in the country, with a long history of crustacean research and the most extensive crustacean collection in the Southern Hemisphere. The Museum is centrally located in the heart of Sydney City and is close to famous landmarks such as the Sydney Opera House and Harbour Bridge, the Royal Botanic Gardens, Art Gallery of New South Wales, the harbour, and hosts numerous tourist attractions, fine dining, and recreational activities.

External links

Conference webpage