16 November 2017

Shinji and colleagues, 2017

Shinji J, Miyanishi H, Gotoh H, Lavine M, Lavine L. 2017. The role of the transcription factor Smox during appendage regeneration in the crayfish Procambarus fallax f. virginalis. Presentation SP06-28 at The Japanese Society of Fisheries Science 85th Anniversary-Commemorative International Symposium, “Fisheries Science for Future Generations,” Tokyo University of Marine Science and Technology, 22 to 24 September 2017. https://www.gakkai-web.net/gakkai/jsfs/sympo/usb/data/html/P02.html

Abstract

Regeneration is a common phenomenon among animals. Members of the phylum Arthropoda, comprising over 80% of total animal species, exhibit strong capacities for regeneration, but little is known about the molecular mechanisms mediating this process. In this study, we investigated the role of the activin signaling pathway in limb regeneration in the decapod crustacean Procambarus fallax f. virginalis. We identified and cloned a downstream transcription factor in the activin pathway, Smox. The Smox gene showed 3 splicing variants, but only one of them encoded a complete Smox transcription factor. Gene knockdown of Smox by RNAi induced formation of smaller limb buds and regeneration of complete but smaller pereopods after autotomy. This indicates that activin signaling via Smox functions in regulation of pereopod size. The expression levels of both Smox and the activin receptor babo were closely correlated with molting. The expression level of Smox during the molting cycle increased when the receptor babo was knocked down by RNAi, indicating that Smox and babo transcription are linked. Our study suggests that the Babo-Smox system in activin signaling is conserved in decapods, and supports an evolutionary conservation of this aspect of molecular signaling during regeneration between protostomes and deuterostomes.

Keywords: None provided.

14 November 2017

Gutekunst, 2017

Gutekunst J. 2017. Clonal genome evolution of the marbled crayfish, Procambarus virginalis. Doctoral thesis, Combined Faculties of Natural Sciences and Mathematics, Ruperto-Carola University Heidelberg. Heidelberg, Germany. 88 pp. https://doi.org/10.11588/heidok.00023501

Abstract

Marbled crayfish (Procambarus virginalis) are the only freshwater crayfish known to reproduce by cloning (apomictic parthenogenesis). Notably, among genetically identical offspring raised in the same environment, distinct phenotypic differences can be observed. These unique characteristics establish the marbled crayfish as a particularly interesting laboratory model. Additionally, parthenogenetic reproduction enables the marbled crayfish to rapidly spread and form stable populations, which poses a serious threat in many freshwater habitats. A further understanding of this organism requires the accessibility of its 3.5 Gbp large genome sequence.

This doctoral thesis provides the first de novo genome assembly of the marbled crayfish. Multiple shotgun and long jumping distance libraries were generated from one individual female, with a single base coverage of over 100×. Sequencing data was used for a first genome assembly with a length weighted median scaffold size (N50) of over 40 kbp. The estimated genome wide heterozygosity rate of 0.53% is substantially higher compared to other arthropod genomes. Transcriptome data enabled the refinement of genetic structures. Eventually, a total of 87.8% complete and 7.4% fragmented single-copy arthropod orthologs were identified using the benchmarking software BUSCO. Single nucleotide variations were analyzed to verify clonality in geographically isolated populations. Results indicate an evolution from a single origin. Moreover, detailed insights into genotype distributions support the theory of asexual speciation by autopolyploidization. Comparison of three Procambarus species indicates detectable genetic separation between marbled crayfish and the closest relative Procambarus fallax. Automatic annotation of 21,000 genes using the annotation pipeline MAKER provides a detailed overview of genetic features. For example, a cellulase gene was identified which potentially plays a key role in omnivorousness. Genomic data and several online services are provided by a central web resource.

This thesis provides detailed genetic insights into the unknown but very versatile order of decapod crustaceans. Considered economically and ecologically relevant keystone species, a representative genome sequence provides an important resource for future research.

Keywords: genome • marbled crayfish • Marmorkrebs • Procambarus • assembly • clonal • parthenogenesis • evolution

03 November 2017

The CABI datasheet

The Centre for Agriculture and Biosciences International (CABI) Invasive Species Compendium has “datasheets, maps, images, abstracts and full text on invasive species of the world.”

Their page on Marmorkrebs is generally very thorough!

Their distribution map seems a little out of date, and has a couple of oddities. For instance, there is one dot right in the middle of the continental United States (roughly in Kansas or Nebraska). This is supposed to represent that Marmorkrebs are available in the pet trade throughout the country, and cite Faulkes (2010) as a resource. Strangely, that paper also found Marmorkrebs for sale as pets in Canada... but there is no dot on the map for Canada.

External links

Invasive Species Compendium - Procambarus fallax f. virginalis (Marmorkrebs)

11 September 2017

Ninth International Crustacean Congress annoucement


The 9th International Crustacean Congress (ICC9) will take place 22-25 May 2018, in Washington DC, USA. The conference website is up, and will soon be available through the The Crustacean Society web page. Registration will open shortly.

I think ICC9 will be the latest “Marmorkrebs on the road” spot, and I hope to meet some fellow marbled crayfish enthusiasts there. I have schemes. Oh yes.


External links

ICC9

09 September 2017

Lipták and colleagues, 2017

Lipták B, Mojžišová M, Gruľa D, Christophoryová J, Jablonski D, Bláha M, Petrusek A, Kouba A. 2017. Slovak section of the Danube has its well-established breeding ground of marbled crayfish Procambarus fallax f. virginalis. Knowledge and Management of Aquatic Ecosystems 418: 40. https://doi.org/10.1051/kmae/2017029

Abstract

Established populations of the non-indigenous parthenogenetically reproducing marbled crayfish Procambarus fallax f. virginalis have been recently reported from various European countries. The colonised sites are usually lentic and relatively isolated from major watercourses and in such cases the immediate threat of the spread of this taxon is limited. Here we report on a marbled crayfish population that is likely to become a seed for colonisation of the Danube in Slovakia. It is located in a channel within the Slovak capital Bratislava in the immediate vicinity of a pumping station that occasionally releases significant amounts of water into the side arm of the Danube. The population is well established with a high growth potential: numerous adult marbled crayfish individuals were observed at the site in September and October 2016 and the progeny (eggs or first two developmental stages) of 27 berried females exceeded 11 000 individuals. The maximum observed fecundity per female reached 647 juveniles in the second developmental stage. The Danube side arm downstream of the pumping station harbours a population of spiny-cheek crayfish Orconectes limosus infected with the crayfish plague pathogen Aphanomyces astaci. We presume that marbled crayfish is already present below the pumping station and it is just a matter of effort and time until it is discovered. The investigated specimens of marbled crayfish were found free of A. astaci, but horizontal transmission from infected spiny-cheek crayfish may be expected, as well as further spread of marbled crayfish in the Danube.

Keywords: pet trade • aquatic invasion • fecundity • asexual reproduction • Slovakia


29 August 2017

Benson and colleagues, 2017

Benson A, Stadele C, Gahrs C, Vidal-Gadea A, Stein W. 2017. Behavioral consequences of RNA-mediated suppression of innexin expression in marbled crayfish. Illinois State University graduate student symposium. Normal, Illinois, March 2017. https://pdfs.semanticscholar.org/bbd8/0f8501fcf81c0605a61fc6cd1622f983f12f.pdf

Abstract

We are using a new genetic model system, the marbled crayfish, Procambarus virginalis, for examining the causal relationship between genes, neurophysiology and behavior. Due to their parthenogenetic reproduction, short reproductive life cycle (mature after 2-3 months) and ex-utero breeding, marbled crayfish are ideal for studying the role of genes in producing behavioral output. We are employing RNA interference (RNAi) to suppress gene expression and cell-specific GFP (green fluorescent protein) expression to identify neurons involved in controlling behavior.

Innexins serve as the structural components of gap junctions in invertebrates and build transmembrane channels that mediate electrical coupling between neurons, and facilitate cell-cell communication through rapid movement of ions, electrical impulses, and small messenger molecules. Currently, eight distinct Innexin genes have been found. Despite a high degree of homology between different species, little is known about the role the different Innexins have in shaping behavior.

We use RNAi to suppress Innexin-4 expression in marbled crayfish. We hypothesize that a reduction inInnexin-4 expression leads to an impairment of walking behavior and a deficit in tail-flip escape responses, since both of these behaviors depend on rapid cell-cell communication through gap junctions. Our analysis revealed that the marbled crayfish Innexin-4 shows strong homology to other invertebrate species (e.g. D. melanogaster and C. elegans). We constructed double stranded RNA (dsRNA, ~800 base pairs) containing exonic regions of the Innexin gene. After direct injection of juvenile marbled crayfish with Innexin-4 dsRNA, we are monitoring the animals for several days to evaluate changes in walking behavior and tail-flip escape responses. Our preliminary data suggest that both behaviors are reduced after Innexin4-RNAi.

Keywords: None provided.

11 August 2017

I got 669 names, and Marmorkrebs ain’t one

A major new crayfish checklist is not available as a preprint. It lists all currently known crayfish species, with a grand total of 669 different species.

I went looking for Marmorkrebs, and found this evaluation of its status:

Unavailable names
Procambarus fallax forma virginalis Martin, Dorn, Kawai, van der Heiden &
Scholtz, 2010: 114.

This interests me for a few reasons. I suspect that this checklist calls Procambarus fallax forma virginalis “unavailable” because the authors (Martin et al. 2010) admitted that the name was a kludge that didn’t follow traditional zoological nomenclature. Martin and colleagues wrote:

If additional data should clarify some of the problematic issues (e.g. confirmation of a single origin and/or the detection of regional populations of the Marmorkrebs in the wild) it should be easy to establish a new species using ‘virginalis’ as epithet.

In 2015, Vogt and colleagues suggested just that: to change the species name of Marmorkrebs to Procambarus virginalis, based on both the genetics and differences like average size.

But so far, the Marmorkrebs community hasn’t bought the arguments for a new species name. I don’t believe I have seen one paper that used “Procambarus virginalis” as the main scientific name. A few have mentioned both names. (In some cases, I was a reviewer on the paper and suggested it would be a good idea).

I’m curious as to what it would take for the Marmorkrebs research community to change the scientific name. And how long it will take to percolate through the scientific literature.

Reference

Crandall KA, De Grave S. An updated classification of  the freshwater crayfishes (Decapoda: Astacidea) of  the world, with a complete species list. Journal of Crustacean Biology: in press. http://dx.doi.org/10.1093/jcbiol/rux070

Martin P, Dorn NJ, Kawai T, van der Heiden C, Scholtz G. 2010. The enigmatic Marmorkrebs (marbled crayfish) is the parthenogenetic form of Procambarus fallax (Hagen, 1870). Contributions to Zoology 79: 107-118. http://dpc.uba.uva.nl/ctz/vol79/nr03/art03