26 April 2017

Could Marmorkrebs be the youngest species?

Q: Which species is the youngest on Earth?

A: Impossible to know for sure, but here is a candidate: the marbled crayfish, also known as Marmorkrebs.

It was discovered in aquariums in the mid 1990s, and has no known natural populations. It’s so unusual that if it was out there, it should have been noticed.

A major genetic difference between Marmorkrebs and their nearest relative is that Marmorkrebs is triploid: it has three sets of chromosomes, not two. The switch from two to three sets of chromosomes can occur in a single step, in one generation.

These give us some reason to believe it literally might not have existed long before the 1990s.

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Which species is the youngest on Earth?

14 April 2017

More Marmorkrebs in Japan

War is in the air. Even against marbled crayfish, with a headline from Japan urging “war” against the species.

A news article is reporting the second finding of Marmorkrebs in Japan, and, worryingly, it reports multiple individuals spread across two years, suggesting a population has been established. And it is on a completely different (and more southern) island than previously. Based on modelling work I helped co-author a few years ago (Faulkes et al. 2012), that region is high quality habitat for Marmorkrebs (see Figure 5 in particular).

The map of Marmorkrebs introductions has been updated, although I suspect the crayfish were not found anywhere near so close to the mouth of the river.


Faulkes Z, Feria TP, Muñoz J. 2012. Do Marmorkrebs, Procambarus fallax f. virginalis, threaten freshwater Japanese ecosystems? Aquatic Biosystems 8: 13. http://dx.doi.org/10.1186/2046-9063-8-13

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War urged to destroy alien cloning mystery crayfish

29 March 2017

Vogt, 2017

Vogt G. 2017. Facilitation of environmental adaptation and evolution by epigenetic phenotype variation: insights from clonal, invasive, polyploid, and domesticated animals. Environmental Epigenetics 3(1): dvx002. http://dx.doi.org/10.1093/eep/dvx002


There is increasing evidence, particularly from plants, that epigenetic mechanisms can contribute to environmental adaptation and evolution. The present article provides an overview on this topic for animals and highlights the special suitability of clonal, invasive, hybrid, polyploid, and domesticated species for environmental and evolutionary epigenetics. Laboratory and field studies with asexually reproducing animals have shown that epigenetically diverse phenotypes can be produced from the same genome either by developmental stochasticity or environmental induction. The analysis of invasions revealed that epigenetic phenotype variation may help to overcome genetic barriers typically associated with invasions such as bottlenecks and inbreeding. Research with hybrids and polyploids established that epigenetic mechanisms are involved in consolidation of speciation by contributing to reproductive isolation and restructuring of the genome in the neo-species. Epigenetic mechanisms may even have the potential to trigger speciation but evidence is still meager. The comparison of domesticated animals and their wild ancestors demonstrated heritability and selectability of phenotype modulating DNA methylation patterns. Hypotheses, model predictions, and empirical results are presented to explain how epigenetic phenotype variation could facilitate adaptation and speciation. Clonal laboratory lineages, monoclonal invaders, and adaptive radiations of different evolutionary age seem particularly suitable to empirically test the proposed ideas. A respective research agenda is presented.

Keywords: epigenetic variation • adaptation • general-purpose genotype • speciation • genome reconfiguration • monoclonal invaders

28 March 2017

More like “guidelines”

Smithsonian Magazine has an article on interesting variations in reproduction featuring eight different species. Marmorkrebs clock in at number three!

Also included are sharks, mollies, lizards, and salamanders. Mammals got nothin’ when it comes to their reproductive practices.

External links

Meet Eight Species That Are Bending the Rules of Reproduction

27 February 2017

Velisek and colleagues, 2017

Velisek J, Stara A, Zuskova E, Kouba A. 2017. Effects of three triazine metabolites and their mixture at environmentally relevant concentrations on early life stages of marbled crayfish (Procambarus fallax f. virginalis). Chemosphere 175: 440-445. http://dx.doi.org/10.1016/j.chemosphere.2017.02.080


The sensitivity of early life stages of marbled crayfish (Procambarus fallax f. virginalis) to chronic exposure of one out of three triazine metabolites (terbuthylazine 2-hydroxy – T2H, terbuthylazine-desethyl – TD, and atrazine 2-hydroxy – A2H) and their mixture at maximal environmentally real concentrations was evaluated under laboratory conditions. The effects were assessed on the basis of mortality, growth, development, oxidative stress biomarkers, antioxidant enzymes activity and histopathology. Single metabolites (T2H – 0.73 μg/L; TD – 1.80 μg/L; A2H – 0.66 μg/L) and their mixture were not associated with negative effects on mortality, behaviour and early ontogeny, however, two metabolites (TD and A2H) and mixtures caused significantly lower growth and significantly higher catalase activity of early life stages of marbled crayfish. No histopathological changes of gills were observed after exposure to all tested triazine treatments, however, apparent histological differences in structural cells organization such as superiority in numbers of lipid resorptive cells were recorded in after exposition to TD and mixture. In conclusion, this study shows potential risk of using triazine herbicides in agriculture due to effects of their degradation products on non-target organisms.

Keywords: antioxidant enzyme • developmental stage • histopathology • oxidative stress • toxicity test

13 February 2017

Koutnik and colleagues, 2017

Koutnik D, Stara A, Zuskova E, Kouba A, Velisek J. 2017. The chronic effects of terbuthylazine-2-hydroxy on early life stages of marbled crayfish (Procambarus fallax f. virginalis). Pesticide Biochemistry and Physiology 136: 29-33. http://dx.doi.org/10.1016/j.pestbp.2016.08.008


This study assessed the chronic effects of terbuthylazine-2-hydroxy (T2H), one of the main terbuthylazine degradation products, on early life stages of marbled crayfish (Procambarus fallax f. virginalis) by means of mortality, growth rate, early ontogeny, oxidative stress, antioxidant defence and histopathology. The crayfish were exposed to four concentrations of the tested substance as follows: 0.75 μg/l (environmental concentration), 75, 375 and 750 μg/l for 62 days. Concentrations over 75 μg/l caused lower weight compared to the control group. T2H at 750 μg/l caused delay in ontogenetic development. Levels of thiobarbituric acid reactive substances and total superoxide dismutase activity were significantly (p < 0.01) lower in groups exposed to 375 and 750 μg/l T2H. Crayfish in these treatments also showed alteration of tubular system including disintegration of tubular epithelium with complete loss of structure in some places of hepatopancreas and wall thinning up to disintegration of branchial filaments with focal infiltrations of hemocytes. In conclusion, chronic terbuthylazine-2-hydroxy exposure in concentrations up 75 μg/l (100 times higher than environmental concentration) affected growth, ontogenetic development, antioxidant system, caused oxidative stress and pathological changes in hepatopancreas of early life stages of marbled crayfish.

Keywords: triazine • early development • histopathology • oxidative stress •antioxidant enzymes

08 February 2017

Eighteenth Crustaceologentagung

The 18th meeting of German speaking carcinologists (Crustaceologentagung) will be held from 30 March to 2 April 2017 at the Humboldt-Universität zu Berlin. Visit the website (and maybe Google Translate) for more information.

Although now that I think about it, if you need Google Translate to understand the web page, you probably wouldn’t get much out of the meeting.

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