2017 was the second best year ever for Marmorkrebs research

This is an annual tradition here on the Marmorkrebs blog! It’s fun to make this graph longer and longer every year...

In terms of straight journal articles, 2017 was tied with 2016: fifteen each. There was just no book dropping a set of chapters to lift the total like last year

There were some significant papers this year. There was a proposal to elevate Marmorkrebs to its own species. Part of this included deposition of reference specimens in a museum, which should be a useful long-term resource, regardless of whether the community moves to the proposed new species name, Procambarus virginalis.

The number of introduced populations continued to increase, with more reports in the scientific literature of European locations and newspaper reports of more discoveries in Japan.

And perhaps most excitingly for next year, there were several doctoral theses that will hopefully become publications in the near future. Maybe even 2018! (One paper, by Císař and others, has already been published with a 2018 publication date.)

The overall trendline still shows no sign of flattening.

Related posts

2008 was the best year ever for Marmorkrebs research
2009 was tied for the best year ever in Marmorkrebs research
2010 was the best year ever for Marmorkrebs research
2011 was not the best year ever for Marmorkrebs research
2012 was an average year for Marmorkrebs research
2013 was the second best year ever for Marmorkrebs research
2014 was a good year for Marmorkrebs research
2015 was the best year ever for Marmorkrebs research

2016 was the best year ever for Marmorkrebs research

Císař and colleagues, 2018

Císař P, Saberioon M, Kozák P, Pautsina A. 2018. Fully contactless system for crayfish heartbeat monitoring: undisturbed crayfish as bio-indicator. Sensors and Actuators B: Chemical 255(1): 29-34. https://doi.org/10.1016/j.snb.2017.07.160

Abstract

The crayfish is widely accepted as very sensitive and fast bio-indicator of changes in water quality. Studies based on heart beat analysis demonstrated the potential of using crayfish as a detector of pollutants consequently several computer-aided systems were developed to use this mechanism. The main complication with applying such a system is the necessity of using metal wires or optical fibres to transmit the signal from sensor which is placed on back of the crayfish to the processing hardware; these attachments restrict system design to one crayfish in one aquarium. We introduced an original system for crayfish heart beat monitoring based on completely non-invasive/contactless hardware. The system can determine crayfish heart beat frequency using only the combination of near infra-red (NIR) illuminator and sensitive camera. The heart rate is the only parameter needed in most of the studies using crayfish as a bio-indicator. We developed the system which needs no attachment, so more crayfish in one aquarium can be monitored simultaneously and it provides accurate information on heart rate and crayfish need no adaptation to the system. It can be used as equivalent to existing systems to simplify the crayfish studies.

Keywords: crayfish • bio-indicator • heart rate • contactless • non-invasive • water quality

Veselý and colleagues, 2017

Veselý L, Boukal DS, Buřič M, Kozák P, Kouba A, Sentis A. 2017. Effects of prey density, temperature and predator diversity on nonconsumptive predator-driven mortality in a freshwater food web. Scientific Reports 7: 18075. https://doi.org/10.1038/s41598-017-17998-4

Abstract

Nonconsumptive predator-driven mortality (NCM), defined as prey mortality due to predation that does not result in prey consumption, is an underestimated component of predator-prey interactions with possible implications for population dynamics and ecosystem functioning. However, the biotic and abiotic factors influencing this mortality component remain largely unexplored, leaving a gap in our understanding of the impacts of environmental change on ecological communities. We investigated the effects of temperature, prey density, and predator diversity and density on NCM in an aquatic food web module composed of dragonfly larvae (Aeshna cyanea) and marbled crayfish (Procambarus fallax f. virginalis) preying on common carp (Cyprinus carpio) fry. We found that NCM increased with prey density and depended on the functional diversity and density of the predator community. Warming significantly reduced NCM only in the dragonfly larvae but the magnitude depended on dragonfly larvae density. Our results indicate that energy transfer across trophic levels is more efficient due to lower NCM in functionally diverse predator communities, at lower resource densities and at higher temperatures. This suggests that environmental changes such as climate warming and reduced resource availability could increase the efficiency of energy transfer in food webs only if functionally diverse predator communities are conserved.

Keywords: None provided.

Levy and colleagues, 2017

Levy T, Rosen O, Simons O, Alkalay AS, Sagi A. 2017. The gene encoding the insulin-like androgenic gland hormone in an all-female parthenogenetic crayfish. PLOS ONE 12(12): e0189982. https://doi.org/10.1371/journal.pone.0189982

Abstract

Male sexual differentiation in crustaceans is controlled by the androgenic gland (AG), a unique male endocrine organ that, in decapods, is located at the base of the 5th pereiopod. In these animals, the insulin-like androgenic gland hormone (IAG) is the major factor secreted from the AG to induce masculinization and maintain male characteristics. It has, however, recently been proposed that this hormone also plays a role in growth and ovarian development in females. In this study, we tested such a possibility by searching for the IAG gene in the marbled crayfish, a parthenogenetic animal that reproduces asexually to form an all-female genetic clone. Based on the phylogenetic relationship between the marbled crayfish and Procambarus fallax, a gonochoristic species of the same North American Cambaridae family, we searched for the IAG gene in the marbled crayfish and then fully sequenced it. The open reading frame of the gene was found to be completely identical in the two species, and their introns shared over 94% identity. It was also found that, in addition to its expression at the base of the 5th pereiopod and in the testes of male P. fallax crayfish, IAG was expressed in the muscle tissue of P. fallax males and females and even of the parthenogenetic marbled crayfish. These findings provide new insight into possible functions of IAG, in addition to its role as a masculinization-inducing factor, and also constitute the basis for a discussion of the evolutionary relationship between the above two species.

Keywords: None provided.

22nd International Symposium on Freshwater Crayfish announcement

The eastern US is the plce to be for crustacean research next year. It will not only host the International Crustacean Congress in Washington, it will be hosting the next Astacology meeting in Pittsburgh. Mark your calendars for 9-13 July 2018!

External links

IAA22 meeting announcement

Lyko, 2017

Lyko F. 2017. The marbled crayfish (Decapoda: Cambaridae) represents an independent new species. Zootaxa 4363(4): 544-552. https://doi.org/10.11646/zootaxa.4363.4.6

Abstract

Marbled crayfish are a globally expanding population of parthenogenetically reproducing freshwater decapods. They are closely related to the sexually reproducing slough crayfish, Procambarus fallax, which is native to the southeastern United States. Previous studies have shown that marbled crayfish are morphologically very similar to P. fallax. However, different fitness traits, reproductive incompatibility and substantial genetic differences suggest that the marbled crayfish should be considered an independent species. This article provides its formal description and scientific name, Procambarus virginalis sp. nov.

Keywords: Crustacea • parthenogenesis • annulus ventralis • genetic analysis • mitochondrial DNA

Marenkov and colleagues, 2017

Marenkov O, Kovalchuk J, Shapovalenko Z, Naboka O, Nesterenko O, Dzhobolda B. 2017. Parameters of the histological adaptation of Marmorkrebs Procambarus fallax f. virginal (sic) (Decapoda, Cambaridae) to zinc and cadmium ions pollution. World Scientific News 90: 189-202. http://www.worldscientificnews.com/wp-content/uploads/2017/08/WSN-90-2017-189-202.pdf

Abstract

Due to the fact that marbled crayfish (Marmorkrebs) got into the reservoirs of the Dnipropetrovsk region in 2015, it was necessary to study the possibilities of its adaptation to environmental factors of reservoirs for further prediction of its distribution or even acclimatization under conditions of toxicological contamination of the ponds of the steppe Prydniprovya. The article presents the results of studies on the influence of heavy metal ions on marbled crayfish. It was determined that zinc and cadmium ions affect weight indicators, survival and reproduction of experimental crayfish. Experimentally simulated concentrations of heavy metals on the example of zinc – 0.1 mg/l (10 MPC) and cadmium – 0.01 mg/l (2 MPC) allowed detecting the reaction of the excretory system of marbled crayfish. It is determined that under the influence of heavy metal ions the area of glandulocytes cells decreases by 10.4–14.8%. Also, there is a decrease in the cellular nucleus, thus, under the influence of zinc, the nucleus of the secretory cells was 23.6% smaller, and under the influence of cadmium by 17.5%. To study the influence of zinc and cadmium on the glandular cells of the green gland of marbled crayfish, the index of nuclear-cytoplasmic ratio (NCR) was used. The indicator of nuclear-cytoplasmic ratio allows estimating the level of metabolism and detecting the manifestation of compensatory reactions of the organism of experimental crayfish. The value of NCR in the experiment and control was not statistically different and ranged from 0.29 to 0.31 units. This indicates an interproportional reduction in both the cytoplasm of the cells of the green gland and their nuclei, caused by heavy metals exposure. The negative influence of heavy metals on the histostructure of hepatopancreas of marbled crayfish was determined; significant changes in the structure of tissue were noted, heavy metals influenced the shape of the hepatopancerase lobes and the size of the lumen. The worst histological picture of cells of experimental tissues and organs of marbled crayfish was observed in individuals exposed to cadmium ions due to the toxicological effects of this heavy metal. Investigation of the histological structure of tissues and organs of marbled crayfish will allow the development of measures for the determination of biomarkers for the bioindication of the aquatic environment using freshwater crayfish. The results of such studies have an important fundamental and applied significance for understanding the mechanisms of adaptation of crustaceans to the conditions of toxicological burden on aquatic ecosystems.

Keywords: Procambarus fallax f. virginalis Martin et al., 2010 • marbled crayfish • heavy metals • glandulocytes • hepatopancreas

(Edit, 13 September 2018: This entry was originally posted with the authors’ given names and surnames reversed. Apologies for the confusion.)

Penk and colleagues, 2017

Penk M, Saul W-C, Dick JTA, Donohue I, Alexander ME, Linzmaier S, Jeschke JM. 2017. A trophic interaction framework for identifying the invasive capacity of novel organisms. Methods in Ecology and Evolution 8(12): 1786–1794. http://dx.doi.org/10.1111/2041-210X.12817

Abstract

1. The likelihood and impacts of invasions by novel organisms (e.g. non-native species, genetically-modified organisms) on the composition and functioning of receiving biological communities hinges on their capacity to exploit resources and/or avoid predation relative to resident counterparts. While assessment of invasion risk based on the comparison of functional responses (per-capita consumption rate as a function of resource density) of novel species with native analogues has been gaining popularity, it may be undermined if alternative prey and potential predators are not represented realistically.

2. Here, we propose a conceptual framework that enables rigorous identification of trophic traits conducive to invasion success by novel organisms – irrespective of their trophic position – and their likely ecological impacts, given their arrival and establishment. We focus on consumption here, but our framework can also be used for autotrophic energy acquisition, and extended to non-trophic and indirect interactions.

3. The framework enables a structured and prioritised selection of subsets of trophic links for invasion risk assessment. It is based on foraging theory and advances in comparative functional responses in invasion ecology. It can even be used in the absence of a resident comparator organism and when resources or predators are only partly known.

4. Our approach enhances the predictive power of species screening, and thus advances prevention and management of invasions under a common framework for all types of novel organisms.

Keywords: Alien species • dietary generalism • ecological novelty • GMO • invasion success • functional responses • predator-prey trophic interactions • risk assessment

Pârvulescu and colleagues, 2017

Pârvulescu L, Togor A, Lele S-F, Scheu S, Șinca D, Panteleit J. 2017. First established population of marbled crayfish Procambarus fallax (Hagen, 1870) f. virginalis (Decapoda, Cambaridae) in Romania. BioInvasions Records 6(4): 357-362. https://doi.org/10.3391/bir.2017.6.4.09

Abstract

The marbled crayfish, Procambarus fallax f. virginialis, is an obligate parthenogenetic crayfish species, its spread in the wild being linked to the aquarium pet-trade. Forty-two adult individuals were found for the first time in Romania in the semi-natural ponds in Băile Felix, near Oradea. Nine ovigerous females were captured as evidence that the population is breeding in the wild. They probably originated from the pet trade and were released by hobbyists into the pond. Microsatellite analysis revealed the same allelic patterns as in a previous study, confirming that these marbled crayfish are parthenogenetic and originate from a single individual. The crayfish plague pathogen Aphanomyces astaci was not present in the population. The site inhabited by this established marbled crayfish population is supplied with water by thermal underground streams, ensuring a constant high temperature. The nearby Peța Natural Reserve protects several endemic species that could be threatened by the further range extension of marbled crayfish. Special protection measures are therefore urgently needed.

Keywords: invasive species • Marmorkrebs • parthenogenesis • pet trade

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.

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

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)

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

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

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.

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

Shiratori and colleagues, 2017

Shiratori C, Suzuki N, Momohara Y, Shiraishi K, Aonuma H Nagayama T. 2017. Cyclic AMP-regulated opposing and parallel effects of serotonin and dopamine on phototaxis in the Marmorkrebs (marbled crayfish). European Journal of Neuroscience 46(3): 1863–1874. https://doi.org/10.1111/ejn.13632

Abstract

Phototactic behaviors are observed from prokaryotes to amphibians and are a basic form of orientation. We show that the marbled crayfish displays phototaxis in which the behavioral response reverse from negative to positive depending on external light conditions. Animals reared in a 12L/12D light cycle showed negative phototaxis during day-time and positive phototaxis during night-time. Animals reared under constant light conditioning showed negative phototaxis during day- and night-time, while animals reared under constant dark conditioning showed positive phototaxis during day- and night-time. Injection of serotonin leads to a reversal of negative to positive phototaxis in both light/dark-reared and light/light-reared animals while injection of dopamine induced reversed negative phototaxis in dark/dark-reared animals. Four hours of dark adaptation were enough for light/dark-reared animals to reverse phototaxis from negative to positive. Injection of a serotonin 5HT₁ receptor antagonist blocked the reverse phototaxis while serotonin 5HT₂ receptor antagonists had no effects. Similarly, dark/dark-reared animals reversed to showing negative phototaxis after 4 hours of light adaptation. Injection of a dopamine DA₁ receptor antagonist blocked this reverse phototaxis, while dopamine DA₂ receptor antagonists had no effects. Injection of a cAMP analogue into light/dark-reared animals blocked reverse phototaxis after dark adaptation, while adenylate cyclase inhibitor in dark/dark-reared animals blocked reverse phototaxis after light adaptation. These results strongly suggest that serotonin mediates positive phototaxis owing to decreased cAMP levels, while dopamine-mediated negative phototaxis occurs due to increased cAMP levels. Supporting this, the ratio of serotonin to dopamine in the brain was much higher in dark/dark-reared than light/dark-reared animals

Keywords: crayfish • taxis • biogenic amines • second messenger • circadian rhythm

The Lausanne Resolution turns 30

Today marks the 30^th anniversary of the Lausanne Resolution, when the world’s leading crayfish experts of the day said to governments, “Stop importing crayfish.”

All of the points listed as reasons to support the resolution are still true.

The resolution is currently up on the International Association for Astacology website as a scanned PDF). This was published in an issue of the journal Freshwater Crayfish (volume 7, page XI), although no PDF of that issue is online yet. I am reproducing it here so that there is a version on the web that is more readily available, discoverable by search engines, and shared, either on social media or by good ol’ cutting and pasting.

RESOLUTION

7^th International Symposium of Astacology - Lausanne, Switzerland,

August 5, 1987

---

The Astacologists of the International Association of Astacology meeting in its seventh International symposium in Lausanne, Switzerland, August 3-5, 1987, have noted:

• the damaging effects to live crayfish markets following the drastic decline in Turkish crayfish production,
• the marketing of new living crayfish species from many different places,
• the total absence of guarantees that such crayfish do not carry communicable parasites and diseases.
• the appearance of epidemics in European crayfish of aphanomycosis (the crayfish plague parasite), especially where it has not previously existed,
• the accrued risks of transmission of parasites and diseases, especially aphanomycosis, from other crayfish populations to native crayfish,
• the grave menace to native crayfish populations from introduction of undesirable exotic crayfish, and
• the potential for exposing fish to diseases and parasites born by crayfish.

Therefore, in view of the need for conservation of indigenous species and populations, we recommend that Governments find the means to stop the importation of living crayfish into their countries for any purpose (food, fish bait, pets, etc.), except for governmentally approved research, restockings or introductions.

Further, those Governments should be responsible for assuring that such living crayfish are parasite and disease free. Finally, Governments should encourage the restoration of native crayfish stocks wherever possible.

We encourage the immediate international adoption of this resolution.

---

Reference

International Association of Astacology. 1988. Lausanne Resolution. Freshwater Crayfish 7: XI. http://www.freshwatercrayfish.org/docs/Lausanne_Resolution_1987.pdf

Hagen, 1870

Hagen HA. 1870. Monograph of the North American Astacidae. Illustrated Catalogue of the Museum of Comparative Zoology at Harvard College 3: 1-109. http://dx.doi.org/10.5962/bhl.title.4923

Abstract

Without abstract. First paragraph of Introduction:

The following monograph of the Fresh-water Crawfishes of North America is intended to form the first step in a scientific examination of the rich crustacean materials contained in the Museum of Comparative Zoology at Harvard College, in Cambridge. The excellent monograph of the genus Callinectes, published by Mr. A. Ordway in 1863, is the only work about Crustacea, based principally upon the Cambridge collection.

Keywords: None provided.

Note: While doing some research to make a point, I discovered that the original species description for Procambarus fallax, the sexual form of Marmorkrebs, is available online. Since taxonomic sources are not cited anywhere near often enough, I include it here. The Procambarus fallax description is on pages 45 and 46 (mostly in Latin).

Biffis, 2017

Biffis C. 2017. Comparative studies in the development of the nervous system in malacostracan crustaceans. Doctoral dissertation, Biology, Humboldt-Universität zu Berlin. http://dx.doi.org/10.18452/18061

Abstract

The present study addresses the development of the nervous system in three malacostracans species: the euphausiacean Meganyctiphanes norvegica, and the two decapods Penaeus monodon (Dendrobranchiata) and Procambarus fallax f. virginalis (Astacida). Based on the use of antibody stainings and fluorescent dyes in combination with CLSM and 3D reconstruction, the observations cover the onset of axogenesis and follow the establishment of the axonal scaffold in a consistent and comprehensive sequence through the embryonic and the post-embryonic development. The development of the nervous system reveals a general developmental pattern shared by the three investigated species. With a comparative approach, the observed pattern is discussed with respect to the segmental organization of the animals’ body. In particular, the development of the peripheral and of the enteric nervous systems plays a crucial role in the process of guiding the main axonal scaffold. In this context, the medulla terminalis, which in the nauplius larvae of M. norvegica and P. monodon develops strictly associated to a pair of frontal sensory organs, is proposed as a separate unit and not part of the tripartite brain. The homology of these sensory organs with the “frontal filaments” of non-malacostracan crustaceans and a new interpretation of the so called “lateral protocerebrum” in the developmental ground pattern of the Crustacea are discussed against the current phylogenetic background. Moreover, the present study offers a precise identification of the single structures forming the stomatogastric nervous system and provides a review of the former nomenclature. The interpretation of the labrum as a non-segmental appendage associated to the stomatogastric nervous system is advanced. Finally, the present study proposes the development of the nervous system as the result of the coordinated interaction of three independent nervous systems, i.e. the central, the enteric and the peripheral. As a consequence, the development of the axonal scaffold, i.e. the formation of the basal network of afferents and efferents necessary for the connection among these three systems, appears uncoupled from the segmentation process.

Keywords: None provided.

Kukule Kankanamge, 2017

Kukule Kankanamge M. 2017. Analysis of chitinase activity. Master’s thesis, Biological Sciences, Bowling Green State University, Bowling Green, Ohio. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1498843764486231

Abstract

The oomycete Aphanomyces astaci infects crayfish, which can result in the mass mortality commonly referred to as “crayfish plague.” Additional oomycetes in the genera Aphanomyces and Saprolegnia also infect crayfish. In the present study, two distinct organisms were isolated and identified from infected marbled crayfish Procambarus fallax forma virginalis and two phylogenetic trees based on internal transcribed spacer I (ITSI) were constructed using MEGA 7 software and maximum likelihood method with 1000 bootstraps. It is known that crayfish pathogens that infect crayfish produce chitinases that enable them to penetrate the cuticle of the crayfish. Preliminary testing for chitinase activity of Aphanomyces sp. indicated that in vitro growth in terms of surface area of the plates covered by mycelia and dry weight of mycelia increased with increasing chitin concentration from 1%-3% and leveled off at 4% chitin. The effects of chitin on timing of sporangia formation and zoospore release of Apahanomyces sp. suggested that chitin plays a role in asexual reproduction of the pathogen. The time taken for Aphanomyces sp. to develop sporangia and zoospore release increased with the amount of chitin incorporated in the media. Based on these observations, isolates of Aphanomyces sp. and of Saprolegnia sp. were tested for their chitinase activity. Both isolates could utilize chitin as carbon and nitrogen source in their growth. Additional experiments suggested that the chitinase activity of Aphanomyces sp. and Saprolegnia sp. involved an unidentified acidic substance produced by both organisms. Dinitrosalicylic acid assay (DNS assay) indicated the presence of unidentified secondary metabolites and/or pigment produced by Saprolegnia sp. and Aphanomyces sp.in nutrient deprived media. In DNS assay, the media with chitin and water in which both pathogens were grown showed highest absorbance after 72 hours indicating the possibility of their maximum production of chitinase and other enzymes within 48-72 hours. Based on the average absorbance readings, Aphanomyces sp. could be producing significantly higher amount of enzymes that break down chitinous cuticle compared to Saprolegnia sp. Overall, the observations made in this study could indicate chitinase production in Aphanomyces sp. and Saprolegnia sp.

Keywords: crayfish pathogen • Aphanomyces astaci • Saprolegnia sp. • chitinase • dinitro salicylic acid assay

Vodovsky and colleagues, 2017

Vodovsky N, Patoka J, Kouba A. 2017. Ecosystem of Caspian Sea threatened by pet-traded non-indigenous crayfish. Biological Invasions 19(7): 2207–2217. https://doi.org/10.1007/s10530-017-1433-1

Abstract

Freshwater ecosystems are particularly vulnerable to biological invasions; the aquatic animal pet trade has been recognized as a significant pathway of introductions. Crayfish are considered a model group of traded organisms with a series of highly successful species already established in the wild, having the potential to negatively influence both indigenous crayfish species (ICS) as well as alter occupied ecosystems. Eastern Europe includes the entire native ranges of indigenous Astacus leptodactylus sensu lato and A. pachypus. This region has been largely overlooked and considered relatively safe from the adverse impacts of non-indigenous crayfish species (NICS). In this study, we evaluated the crayfish pet trade in the Lower Volga Region with special emphasis on Astrakhan, the biggest city of Russian Federation in the region located just in the delta of Volga River, thus being a potential gateway of introductions to the Caspian Sea and adjacent freshwaters. The local pet trade involves 12 NICS. Considering their origin, availability, probability of establishment, invasiveness and further aspects, Procambarus fallax f. virginalis, P. clarkii and Cherax destructor are considered potentially the most problematic, including transmission of diseases like crayfish plague caused by Aphanomyces astaci or white spot syndrome virus. Taking this information as a whole, the availability of NICS with a high probability of overlapping the entire range of European ICS means that attention is warranted. Further research is needed to corroborate the abilities of NICS and their associated diseases to withstand specific conditions of the Caspian Sea as well as the adjacent Black and Azov Seas, all possessing different degrees of elevated salinity.

Keywords: aquarium • invasiveness • ornamental animal • Pet trade • Russian Federation • salinity

Uderbayev and colleagues, 2017

Uderbayev T, Patoka J, Beisembayev R, Petrtý M, Bláha M, Kouba A. 2017. Risk assessment of pet-traded decapod crustaceans in the Republic of Kazakhstan, the leading country in Central Asia. Knowledge and Management of Aquatic Ecosystems 418: 30. https://doi.org/10.1051/kmae/2017018

Abstract

The pet trade with decapod crustaceans has been considered one of the main pathway of introduction of these animals worldwide. As the leading markets in this regards are the Czech Republic, Germany and the USA. Central Asia is not perceived as an important market with ornamental decapod crustaceans. Despite this assumption, we found at least 16 species of freshwater shrimp, crayfish and crab species pet-traded in the Republic of Kazakhstan, the largest country in this region. Considering computed risk assessment, the origin of particular species, their availability on the market, the probability of establishment and further aspects, we identified two crayfish Procambarus clarkii and Procambarus fallax f. virginalis being the seriously hazardous taxa with high potential to threaten native crayfish species as well as inhabited ecosystems. To prevent their introductions and to minimize the risks of mentioned species, similarly as in the case of European Union, we recommend the total ban of import, trade and keeping of these high-risk taxa within Central Asia.

Keywords: Biological invasion • climate matching • introduction pathway • Procambarus clarkii • Procambarus fallax f. virginalis

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.)

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.

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

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?

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

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

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

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

Abstract

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

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

Abstract

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

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.

External links

Crustaceologentagung

How could I miss Croatia?

I’m red-faced. It’s about two years since a short note appeared mentioning the discovery of Marmorkrebs in northern Croatia (Samardžić et al. 2014). This is one I should have caught, too, since it appeared in the newsletter of the International Association of Astacology, of which I am a member! Always read the newsletters of your professional societies, citizens!

I have updated the map of Marmorkrebs introductions with this record, and others (more recent – hadn’t missed them,. just hadn’t added them) in the Czech republic.

Reference

Patoka J, Buric M, Kolár V, Bláha M, Petrtýl M, Franta P, Tropek R, Kalous L, Petrusek A, Kouba A. 2016. Predictions of marbled crayfish establishment in conurbations fulfilled: evidences from the Czech Republic. Biologia 71(12): 1380–1385. https://doi.org/10.1515/biolog-2016-0164

Samardžić M, Lucić A, Maguire I, Hudina S. 2014. The first record of the marbled crayfish (Procambarus fallax (Hagen, 1870) f. virginalis) in Croatia. Crayfish News 36(4): 4. http://www.freshwatercrayfish.org/docs/cn/CrayfishNews_36(4)_hr.pdf

Call for crustacean papers: Fishes

Even though I have been a working professional scientist for some time, there are always more journals than time, so I am always on the lookout for journals that would be appropriate for Marmorkrebs papers.

When I first saw the journal Fishes, I though, “This is not for me, because I don’t study animals with backbones.” But despite the title, Fishes takes papers on invertebrates, too. The journal’s mandate includes “aquatic life science and aquatic animals (fishes, molluscs and crustaceans, both fresh water and marine).”

Fishes caught my eye for a few reasons.

It is a new journal, it is open access, and they are waiving article processing charges for articles published in 2017. Given that the main reason I see people not publishing open access is that people are unable to pay article processing fees, offering free publication as an “introductory offer,” as it were, is interesting to many researcher.

That said, while this journal doesn’t have much of a track record yet, the publisher, MDPI, has a mixed track record at best.

In brief, on the negative column, MDPI journals have published several very poor papers. They have also sent out a lot of unsolicited emails (this post was prompted by one).

On the positives column, MDPI is a member of the Directory of Open Access Journals and the Committe on Publication Ethics. The Fishes editor-in-chief appears to be a real person. Richard Poynder has a thorough article and interview from 2015 covering the debates about whether the Fishes publisher could be rightfully called a “predatory publisher.” Scammers are typically not as transparent as MDPI owner Shu-Kun Lin is in this interview, although some of his answers give me pause.

And publishing articles for free – as Fishes is doing this year – would be an incredibly bad scam.

External links

Fishes

The Open Access Interviews: Publisher MDPI

Is MDPI a reputable Academic Publisher?

New International Association for Astacology website

 The new site for the professional society for all things crayfish is now:

Freshwatercrayfish.org

The relaunch is looking pretty sharp, I must say! The landing page has a lovely rotating gallery of very high resolution crayfish pictures.

Falckenhayn, 2016

Falckenhayn C. 2016. The methylome of the marbled crayfish Procambarus virginalis. Doctoral dissertation, Combined Faculties for the Natural Sciences and for Mathematics, University of Heidelberg, Heidelberg. http://archiv.ub.uni-heidelberg.de/volltextserver/22489/1/Falckenhayn_Cassandra_PhDThesis.pdf

Abstract

DNA methylation in invertebrates seems to play a different role as in mammals and its evolutionary conservation among invertebrates is unclear. Only two studies describe crustacean methylomes giving just a small overview. The parthenogenetic reproducing marbled crayfish display a high environmental adaptability besides its genetic uniformity and thus, possess the necessary attributes of a laboratory model organism. The aim of this work was to characterize the methylome of the marbled crayfish at single-base resolution using whole-genome bisulfite sequencing in an attempt to give new insights into DNA methylation in crustaceans and thus, in the evolutionary conservation among invertebrates. Analysis of the mitochondrial DNA of different marbled crayfish strains revealed a single origin and suggests to consider the marbled crayfish as independent asexual species Procambarus virginalis. Furthermore, since the P. virginalis possess a large genome size, the transcriptome was assembled and comparison to other species revealed a relative good quality of the first draft transcriptome as well as the presence of a conserved DNA methylation system in P. virginalis. Analysis of the CpG depletion in protein-coding sequences and mass spectrometry confirmed historical germline and current DNA methylation in various tissues of P. virginalis. The methylome was characterized by the key features of animal methylomes with methylation targeted to gene bodies. The gene bodies displayed the typical pattern of a mosaically methylated invertebrate genome and a bimodal distribution of their methylation levels. Targeted gene bodies were annotated as housekeeping genes and methylation showed a parabolic relationship to housekeeping gene expression suggesting that the DNA methylation of housekeeping genes might fine-tune their expression. Additionally, repeats were generally hypomethylated and the methylation of repeats depended on their position to gene bodies. Finally, inter-individual and inter-tissue comparison of gene body methylation revealed a high reproducibility of the methylation patterns, while inter-species comparison between P. fallax and P. virginalis displayed an overall hypomethylation in the P. virginalis genes which however, could not explain the by mass spectrometry detected global hypomethylation in P. virginalis. These findings uncovered that the P. virginalis methylome is characterized by tissue-invariant housekeeping gene methylation. This thesis describes novel insights into the evolutionary conservation of gene body and repeat methylation in invertebrates, especially crustaceans, and the preferential methylation of housekeeping genes highlights a functional difference to the tissue-specific methylation in mammals.

Keywords: None provided.