22 June 2017

Lyko, 2017

Lyko F. 2017. Ein Krebs für die Krebsforschung. Biologie in unserer Zeit 47(3): 172–177. http://dx.doi.org/10.1002/biuz.201710620

Abstract

Marmorkrebs (or marbled crayfish) is a triploid crayfish known since the mid-1990s, which reproduces parthenogenetically. It originated from the North American decapod species Procambarus fallax and was distributed as a popular aquarium pet. Subsequent anthropogenic releases have resulted in the establishment of several stable populations in the wild that constitute a serious invasive threat. Interestingly, marbled crayfish use a parthenogenetic mode of reproduction that results in the generation of clones with minimal genetic variation. In addition, the animals can be easily bred and manipulated in the laboratory. These features establish marbled crayfish as a novel and innovative model organism for tumor biology, particularly for the analysis of clonal evolution and epigenetic adaptation of tumor genomes.

Keywords: Marmorkrebs • tumor biology • clonal evolution • epigentics

(Note: The main text of the article is in German. Keywords are translated from German.)

12 June 2017

Martin and colleagues, 2016

Martin A, Serano JM, Jarvis E, Bruce HS, Wang J, Ray S, Barker CA, O’Connell LC, Patel NH. 2016. CRISPR/Cas9 mutagenesis reveals versatile roles of Hox genes in crustacean limb specification and evolution. Current Biology 26(1): 14-26. https://doi.org/10.1016/j.cub.2015.11.021

Abstract

Crustaceans possess a diverse array of specialized limbs. Although shifts in Hox gene expression domains have been postulated to play a role in generating this limb diversity, little functional data have been provided to understand the precise roles of Hox genes during crustacean development. We used a combination of CRISPR/Cas9-targeted mutagenesis and RNAi knockdown to decipher the function of the six Hox genes expressed in the developing mouth and trunk of the amphipod Parhyale hawaiensis. These experimentally manipulated animals display specific and striking homeotic transformations. We found that abdominal-A (abd-A) and Abdominal-B (Abd-B) are required for proper posterior patterning, with knockout of Abd-B resulting in an animal with thoracic type legs along what would have been an abdomen, and abd-A disruption generating a simplified body plan characterized by a loss of specialization in both abdominal and thoracic appendages. In the thorax, Ubx is necessary for gill development and for repression of gnathal fate, and Antp dictates claw morphology. In the mouth, Scr and Antp confer the part-gnathal, part-thoracic hybrid identity of the maxilliped, and Scr and Dfd prevent antennal identity in posterior head segments. Our results allow us to define the role Hox genes play in specifying each appendage type in Parhyale, including the modular nature by which some appendages are patterned by Hox gene inputs. In addition, we define how changes in Hox gene expression have generated morphological differences between crustacean species. Finally, we also highlight the utility of CRISPR/Cas9-based somatic mutagenesis in emerging model organisms.

Keywords: None provided.

Note: Marmorkrebs appear in Figure 7D, described in the main text with the incomplete species name, “Procambarus fallax.” The Supplemental Experimental Procedures provide the full name, confirming that these are Marmorkrebs.

23 May 2017

Veselý and colleagues, 2017

Veselý L, Hrbek V, Kozák P, Buřič M, Sousa R, Kouba A. 2017. Salinity tolerance of marbled crayfish Procambarus fallax f. virginalis. Knowledge and Management of Aquatic Ecosystems 418: 21. https://doi.org/10.1051/kmae/2017014

Abstract

Eastern Europe comprises a significant part of the native ranges for indigenous crayfish species (ICS) belonging to the genus Astacus. This region has been largely overlooked by astacologists and considered relatively immune to the impacts of non-indigenous crayfish species (NICS). The recent discovery of two marbled crayfish Procambarus fallax f. virginalis populations in Ukraine has changed this view. Increased propagule pressure (mainly due to pet trade) has raised concerns of NICS which may negatively impair the ecosystems of Azov, Black and Caspian Seas and their tributaries inhabited by ICS. In this study, we provide the first insight into salinity tolerance of marbled crayfish. We performed a 155-day experiment using 5 different salinities (6, 9, 12, 15, and 18 ppt) and a freshwater control. Evaluation of survival, growth and reproduction suggests that marbled crayfish have a lower salinity tolerance than other crayfish species, which may limit their invasive potential in brackish environments. However, its ability to survive for more than 80 days at 18 ppt opens up the possibility of gradual dispersion and adaptation to brackish conditions. Our study highlights the need for further studies elucidating the potential for marbled crayfish to negatively impair these ecosystems.

Keywords: brackish environment • growth • reproduction • moult • survival

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.

External links

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.

References

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

External links

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

Abstract

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