Food preparation

The marbled crayfish are not picky eaters, but they do love their peas. I've noticed, though, that they will often discard the seed coat covering the peas. Consequently, I now remove it before feeding the Marmorkrebs, so that it's one less thing I have to fish out of the tank the next day if there's any excess food.

Pic of the moment: 20 November 2007

A Marmorkrebs embryo at about the half-way point in its development, based on Seitz and colleagues (2005).

Share and share alike

I've spent the last couple of days adding in sharing / social networking / bookmarking tools to this blog. I don't think the process is complete. Compare the list of option currently added on the "Share and subscribe" list (about 9) to the little patchwork quilt of sharing icons that I found on another website (pictured).

While any one of these may be all someone needs as a reader, it's very frustrating as a writer. You want to provide useful tools, but there are so many competing services that it's very hard to stay on top of them all.

Tracking research blogging

Blogger for Peer-Reviewed Research Reporting, also known as BPR3, has made available an icon for blog posts that discuss peer-reviewed research papers. This seems to be a useful idea, and may help separate wheat from chaff. At this point, none of the posts I've made so far qualify on this blog qualify for the icon, as I've simply been collecting published abstracts. As this blog continues, though, I'm quite sure that there will be commentaries on papers.

Transgenic methods

One of the exciting prospects of Marmorkrebs is that any genetic change to an individual should be propagated to all its offspring, so changes introduced by mutations and transgenics would be easily maintained.

Vogt and colleagues (2004) note that Sarmasik and collegues (2001) had successfully transformed the crayfish species Procambarus clarkii. Sarmasik and colleagues based their methods on those of Burns and colleagues (1993) and Yee and colleagues (1994). All of which tells you how to design this stuff from scratch.

Fortunately, this does not appear to be necessary. A pantropic retroviral expression system is available commercially from ClonTech, which seems to be based on the work of Burns and colleagues.

Note, however, that because this is a viral method of delivery, it has a higher biosafety level than many labs might have.

References

Burns JC, Friedmann T, Driever W, Burrascano M, Yee J. 1993. Vesicular stomatitis Virus G glycoprotein pseudotyped retroviral vectors: Concentration to very high titer and efficient gene transfer into mammalian and nonmammalian cells. Proceedings of the National Academy of Sciences 90(17): 8033-8037.
http://www.pnas.org/cgi/content/abstract/90/17/8033

Sarmasik A, Chun CZ, Jang I-K, Lu JK, Chen TT. 2001. Production of transgenic live-bearing fish and crustaceans with replication-defective pantropic retroviral vectors. Marine Biotechnology 3: S177-S184.
http://dx.doi.org/10.1007/s10126-001-0040-3

Sarmasik A, Jang I-K, Chun CZ, Lu JK, Chen TT. 2001. Transgenic live-bearing fish and crustaceans produced by transforming immature gonads with replication-defective pantropic retroviral vectors. Marine Biotechnology 3(5): 470-477.
http://dx.doi.org/10.1007/s10126001-0019-0

Yee J, Miyanohara A, LaPorte P, Bouic K, Burns JC, Friedmann T. 1994. A General method for the generation of high-titer, pantropic retroviral vectors: Highly efficient infection of primary hepatocytes. Proceedings of the National Academy of Sciences 91(20): 9564-9568.
http://dx.doi.org/10.1073/pnas.91.20.9564

The closest relative of Marmorkrebs?

Digging back through the CRUST-L archive again, to bring forth this helpful post from Keith Crandall, dated 24 May 2006.

Scholtz called this crayfish Procambarus fallax in his wonderful paper in Nature describing the most interesting parthenogenesis phenomenon. I was skeptical with that definition (having worked on the Florida crayfish a bit and seeing a picture of the marbled crayfish - it looked much more like a Procambarus alleni to me) and therefore asked a few different folks in Europe to send me tissue samples from the marbled crayfish. I received samples from to different folks (Austria and Germany), sequenced these samples, and compared them to our extensive database of crayfish sequences. Our analyses clearly support the idea that the marble crayfish is indeed a Procambarus alleni - a species native to central and southern Florida in the US.

That said, in some follow-up emails to Keith, he recommended against calling the parthenogenetic marbled crayfish P. alleni and just calling it Marmorkrebs for now.

Vogt and Tolley, 2004

Vogt G & Tolley L. 2004. Brood care in freshwater crayfish and relationship with the offspring's sensory deficiencies. Journal of Morphology 262(2): 566-582.
http://dx.doi.org/10.1002/jmor.10169

Abstract

Prolonged brood care is one of the evolutionary clues for the successful colonization of freshwater habitats by freshwater crayfish (Astacida). By means of macrophotography, light microscopy, and scanning electron microscopy we investigated all phases of brood care in freshwater crayfish, with particular emphasis on the morphological structures involved. We selected the recently discovered parthenogenetic marbled crayfish (species identity not yet known) as a model organism due to its fast reproduction and high resistance to handling stress. In order to examine if there is a causal relationship between brood care and the developmental status of the offspring's sensory apparatus, we additionally investigated major sense organs of juvenile Stages 1-5 in comparison with those of the adults. Brood care in the marbled crayfish is characterized by initial and final active phases dominated by specific maternal or juvenile behavior and a medial passive phase based more on the action of temporarily developed structures rather than on behavior. The most remarkable feature of this period, which includes permanent carrying of the eggs and the first two juvenile stages under the mother's abdomen, is safeguarding of hatching by a telson thread that keeps the helpless newborn hatchlings linked to the egg cases on the maternal pleopods and thus prevents them from being lost. Further important transient structures are the recurved hooks on the first pereiopods of Stage 1 and 2 juveniles that are used to firmly attach these nonfeeding stages to the mother's abdomen. In hatchlings all sense organs necessary for an independent life, such as eyes, olfactory aesthetascs, gustatory fringed setae, hydrodynamic receptor hairs, and statocysts are not developed or are underdeveloped, making brood care indispensable. Most of these sense organs appear in Stage 2 juveniles, but only from Stage 3, the first freelancing and feeding stage, are all sense organs well developed and operating, thus reducing brood care in this final period to temporary provisioning of shelter. Brooding of the eggs and postembryonic brood care are to some extent also found in other freshwater Decapoda like freshwater crabs and aeglid anomurans, but safeguarding of hatching is confined to the Astacida only. This sophisticated mode of passive brood care is unique in the animal kingdom and is apparently related to the sensory deficiencies of the first juvenile stage.

Keywords: marbled crayfish • Decapoda • Crustacea • brood care • hatching • development • sense organs

Schiewek and colleagues, 2007

Schiewek R, Wirtz M, Thiemann M, Plitt K, Vogt G & Schmitz OJ. 2007. Determination of the DNA methylation level of the marbled crayfish: An increase in sample throughput by an optimised sample preparation. Journal of Chromatography B 850(1-2): 548-552.
http://dx.doi.org/10.1016/j.jchromb.2006.11.040

Abstract

Using a previously described capillary electrophoretic method with laser-induced fluorescence detection the genomic methylation level can be determined exactly. We present a sample preparation that eliminates the surplus of fluorescence marker used for coupling resulting in an increase of sample throughput from 75 to 250 analyses per week. The sensitivity of the method was also increased, which allows the determination of methylation levels under 1%. With these changes in sample preparation a methylation level of 1.64 ± 0.03% in hepatopancreas DNA of the recently discovered marbled crayfish could be determined.

Keywords: DNA methylation • 5-Methylcytosine • epigenomics • CE-LIF • marbled crayfish

Early reports from pet owners

I was searching around on some of my old CD backups of data, and I found I had saved a copy of this post from the CRUST-L listserver. To this best of my knowledge, this may have been the first introduction of Marmorkrebs to the English-speaking scientific community. Jeff Shields' comment is wonderfully prescient, as was my recognizing that this post was interesting enough to save, something I don't have a habit of doing.

· · · · ·

Subject: [CRUST-L:629] Re: "Marmor"-Crayfish
Date: Fri, 07 Apr 2000 08:20:57 -0400
From: Jeffrey Shields
To: "Kai A. Quante"
CC: crust-l@VIMS.EDU

Here's an interesting one. Please respond to Kai Quante, and not to me.

Thanks, Jeff

At 11:26 AM 4/7/00 +0200, you wrote:

Hello,

I've a complicated question. Since more than two years it is possible to buy a crayfish in Germany which origin is unknown. The crayfish reaches a maximum sice of 12 cm and is usually brown. In hard alkaline water they become a little bit blue like older ones. In Germany it is called Marmor-Krebs without a scientific name :-(

The interesting thing is that there are reports that crayfishes which were kept alone for there whole life had eggs and childs. All reports say that every crayfish ever kept had eggs once or more in their life....

Please help! We are searching for the scientific name since two years.

THANKS in advance for any kind of help!

Kai

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· · · · ·

The message above has been edited to remove potentially obsolete email addresses and web links. Kai Quante does still maintain an aquarium page, but I do not read German and have no idea if it is still up-to-date. And I see now that there's even links to a webpage on "Marmor-Krebs," with further links to notes on reproduction dating from 1997.

Model for success

The goal is simple: To have Marmorkrebs mentioned in the same breath as those shown on the NIH model organisms page.

This is informing some of my thinking about what to do with the Marmorkrebs.org website and what resources we need. I've been tooling around and looking at some of the other resource webpages.

Zebrafish have ZFIN.org, and C. elegans has wormatlas.org. Fruitflies have Flybase. To name just a few examples.

And it's clear what all of those organisms have in common: they had a massive effort put into a complete description of some aspect of that organism. For C. elegans, it was cataloging the entire nervous system (all 302 neurons) and its embryonic development. Zebrafish was development and genetics. Drosophila, of course, was genetics, genetics, genetics.

Polanska and colleagues, 2007

Polanska MA, Yasuda A & Harzsch S. 2007. Immunolocalisation of crustacean-SIFamide in the median brain and eyestalk neuropils of the marbled crayfish. Cell and Tissue Research 330(2): 331-344. http://dx.doi.org/10.1007/s00441-007-0473-8

Abstract

Crustacean-SIFamide (GYRKPPFNGSIFamide) is a novel neuropeptide that was recently isolated from crayfish nervous tissue. We mapped the localisation of this peptide in the median brain and eyestalk neuropils of the marbled crayfish (Marmorkrebs), a parthenogenetic crustacean. Our experiments showed that crustacean-SIFamide is strongly expressed in all major compartments of the crayfish brain, including all three optic neuropils, the lateral protocerebrum with the hemiellipsoid body, and the medial protocerebrum with the central complex. These findings imply a role of this peptide in visual processing already at the level of the lamina but also at the level of the deeper relay stations. Immunolabelling is particularly strong in the accessory lobes and the deutocerebral olfactory lobes that receive a chemosensory input from the first antennae. Most cells of the olfactory globular tract, a projection neuron pathway that links deuto- and protocerebrum, are labelled. This pathway plays a central role in conveying tactile and olfactory stimuli to the lateral protocerebrum, where this input converges with optic information. Weak labelling is also present in the tritocerebrum that is associated with the mechanosensory second antennae. Taken together, we suggest an important role of crustacean-SIFamidergic neurons in processing high-order, multimodal input in the crayfish brain.

Keywords: Marmorkrebs • brain anatomy • GYRKPPFNGSIFamide • immunolocalisation

Martin and colleagues, 2007

Martin P, Kohlmann K & Scholtz G. 2007. The parthenogenetic Marmorkrebs (marbled crayfish) produces genetically uniform offspring. Naturwissenschaften 94(10): 843-846. http://dx.doi.org/10.1007/s00114-007-0260-0

Abstract

Genetically identical animals are very much in demand as laboratory objects because they allow conclusions about environmental and epigenetic effects on development, structures, and behavior. Furthermore, questions about the relative fitness of various genotypes can be addressed. However, genetically identical animals are relatively rare, in particular, organisms that combine a high reproduction rate and a complex organization. Based on its exclusively parthenogenetic reproduction mode, it has been suggested that the Marmorkrebs (Crustacea, Decapoda, Astacida), a recently discovered crayfish, is an excellent candidate for research addressing the aforementioned questions. However, until now, a study using molecular markers that clearly proves the genetic uniformity of the offspring has been lacking. Here, with this first molecular study, we show that this crayfish indeed produces genetically uniform clones. We tested this with 19 related individuals of various generations of a Marmorkrebs population by means of six different microsatellite markers. We found that all examined specimens were identical in their allelic composition. Furthermore, half of the analyzed loci were heterozygous. These results and the absence of meioses in previous histological studies of the ovaries lead us to conclude the Marmorkrebs propagates apomictically. Thus, a genetically uniform organism with complex morphology, development, and behavior is now available for various laboratory studies.

Keywords: microsatellites • apomictic reproduction • clonal model organism

Vilpoux and colleagues, 2006

Vilpoux K, Sandeman R & Harzsch S. 2006. Early embryonic development of the central nervous system in the Australian crayfish and the Marbled crayfish (Marmorkrebs). Development Genes and Evolution 216(4): 209-223. http://dx.doi.org/10.1007/s00427-005-0055-2

Abstract

This study sets out to provide a systematic analysis of the development of the primordial central nervous system (CNS) in embryos of two decapod crustaceans, the Australian crayfish Cherax destructor (Malacostraca, Decapoda, Astacida) and the parthenogenetic Marbled crayfish (Marmorkrebs, Malacostraca, Decapoda, Astacida) by histochemical labelling with phalloidin, a general marker for actin. One goal of our study was to examine the neurogenesis in these two organisms with a higher temporal resolution than previous studies did. The second goal was to explore if there are any developmental differences between the parthenogenetic Marmorkrebs and the sexually reproducing Australian crayfish. We found that in the embryos of both species the sequence of neurogenetic events and the architecture of the embryonic CNS are identical. The naupliar neuromeres proto-, deuto-, tritocerebrum, and the mandibular neuromeres emerge simultaneously. After this “naupliar brain” has formed, there is a certain time lag before the maxilla one primordium develops and before the more caudal neuromeres follow sequentially in the characteristic anterior–posterior gradient. Because the malacostracan egg-nauplius represents a re-capitulation of a conserved ancestral information, which is expressed during development, we speculate that the naupliar brain also conserves an ancestral piece of information on how the brain architecture of an early crustacean or even arthropod ancestor may have looked like. Furthermore, we compare the architecture of the embryonic crayfish CNS to that of the brain and thoracic neuromeres in insects and discuss the similarities and differences that we found against an evolutionary background.

Keywords: Arthropoda • axogenesis • evolution • neurogenesis • naupliar brain

Alwes and Scholtz, 2006

Alwes F & Scholtz G. 2006. Stages and other aspects of the embryology of the parthenogenetic Marmorkrebs (Decapoda, Reptantia, Astacida). Development Genes and Evolution 216(4): 169-184. http://dx.doi.org/10.1007/s00427-005-0041-8

Abstract

The early development of the parthenogenetic Marmorkrebs (marbled crayfish) is described with respect to external morphology, cell lineage, and segment formation. Due to its parthenogenetic reproduction mode, the question arises whether or not the marbled crayfish is a suitable model organism for developmental approaches. To address this question, we describe several aspects of the embryonic development until hatching. We establish ten stages based on characteristic external changes in the living eggs such as blastoderm formation, gastrulation process, formation and differentiation of the naupliar and post-naupliar segments, limb bud differentiation, and eye differentiation. The study of the post-naupliar cell division patterns, segment formation, and engrailed expression reveals distinct similarities to that of other freshwater crayfish. On this basis, we evaluate the possibility of a generalization of ontogenetic processes in the Marmorkrebs for either freshwater crayfish or other crustacean developmental systems.

Keywords: marbled crayfish • segmentation • cell lineage • Engrailed • Astacida

Seitz and colleagues, 2005

Seitz R, Vilpoux K, Hopp U, Harzsch S & Maier G. 2005. Ontogeny of the Marmorkrebs (marbled crayfish): a parthenogenetic crayfish with unknown origin and phylogenetic position. Journal of Experimental Zoology A 303(5): 393-405. http://dx.doi.org/10.1002/jez.a.143

Abstract

Development, growth, and egg production of the Marmorkrebs (marbled crayfish), a crayfish with parthenogenetic reproduction, uncertain geographic origin, and taxonomic position, was studied under laboratory conditions. Length and weight increments strongly depended on temperature being highest at 30°C, and lowest at 15°C. At 25°C, cephalothorax length and weight increased by 17.5 mm and 1700 mg, respectively, in the course of 150 d, whereas at 15°C these parameters increased by only 7 mm and 100 mg during the same period of time. Photoperiod slightly affected growth at 25°C. During growth experiments, mortality was lower at 20°C compared to higher (25°, 30°C) or lower temperatures (15°C), and lower under short-day than under long-day conditions. Females matured early (at an age of 141-255 d, a cephalothorax length of 14-21.5 mm, and a weight of 0.63-2 g) compared to other crayfish species. Reproductive females with a cephalothorax length of between 25-35 mm produced large clutches (up to 416 eggs) and brooding periods varied between 22 and 42 d. In order to establish a staging scheme for Marmorkrebs embryos, embryos were photographed, externally visible ontogenetic events charted, and dissected embryos stained with a nuclear dye. These experiments indicate that their development is virtually identical to that of other crayfish. In conclusion, these results and others show that the Marmorkrebs may be taken as a representative valid model organism for future developmental studies on Crustacea.

Keywords: None provided.

Vogt and colleagues, 2004

Vogt G, Tolley L, & Scholtz G. 2004. Life stages and reproductive components of the Marmorkrebs (marbled crayfish), the first parthenogenetic decapod crustacean. Journal of Morphology 261(3): 286-311. http://dx.doi.org/10.1002/jmor.10250

Abstract

Recently, we briefly reported on the first case of parthenogenesis in the decapod Crustacea which was found in the Marmorkrebs or marbled crayfish, a cambarid species of unknown geographic origin and species identity. Curiously, this animal is known only from aquarium populations, where it explosively propagates. By means of light and electron microscopic techniques we have now investigated the reproductive components of this crayfish, using more than 100 specimens ranging from hatchling to repeatedly spawned adult. Additionally, we documented its principal life stages. Our results revealed that the external sexual characters and also the gonads of the marbled crayfish are purely female, making this fast-reproducing species a good model for investigating female reproductive features in crayfish. Testicular tissues, ovotestes, or male gonoducts, gonopores, or gonopods were never found, either in small juveniles or large adult specimens, confirming the parthenogenetic nature of this crayfish. Parthenogenesis may have arisen spontaneously or by interspecific hybridization since Wolbachia-like feminizing microorganisms were not found in the ovaries. The external sexual characters of the marbled crayfish are first recognized in Stage 4 juveniles and are structurally complete 2 months after hatching in specimens of 2 cm total length. In the same life stage the ovary is fully differentiated as well, although the oocytes are in previtellogenic and primary vitellogenic stages only. The architecture of the mature ovary and also the synchronous maturation of cohorts of primary vitellogenic oocytes by secondary vitellogenesis are in general agreement with data published on ovaries of bisexual crayfish. New results were obtained with respect to the muscular nature of the ovarian envelope and its extensive proliferation after the first spawning, the distribution of hemal sinuses in the ovarian envelope and in the interstitium around the oogenetic pouches, the high transport activity of the follicle cells, and the colonization of oogenetic pouches by previtellogenic oocytes that originate in the germaria. Investigation of the nuclei of oocytes in the germaria and oogenetic pouches revealed no signs of meiosis, as usually found in females of bisexual decapods, suggesting that parthenogenesis in the marbled crayfish might be an apomictic thelytoky. The detection of new rickettsial and coccidian infections in the ovary and further organs raises fears that the marbled crayfish might endanger native European species by transmission of pathogens once escaped into the wild.

Keywords: marbled crayfish • Decapoda • life stages • reproduction • parthenogenesis • ovary • diseases

Scholtz and colleagues, 2003

As new papers on Marmorkrebs are published, I will post the abstracts here, to facilitate searches. Meanwhile, I will add already published papers in roughly chronological order.

• • • • •

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. http://dx.doi.org/10.1038/421806a

Abstract

It has been rumoured that an unidentified decapod crustacean, a crayfish of marbled appearance and of uncertain geographical origin that was introduced into the German aquarium trade in the mid-1990s, is capable of unisexual reproduction (parthenogenesis). Here we confirm that this marbled crayfish ('Marmorkrebs') is parthenogenetic under laboratory conditions and use morphological and molecular analysis to show that it belongs to the American Cambaridae family. Although parthenogenesis is widespread among the Crustacea, and shrimp, lobsters, crayfish and crabs are otherwise versatile in their modes of reproduction, it has not been reported before in decapods, the largest and economically most important crustacean group. By virtue of its parthenogenetic reproduction, the marbled crayfish emerges not only as an interesting laboratory model but also as a potential ecological threat in that it could outcompete native forms should even a single specimen be released into European lakes and rivers.

Keywords: None provided.

An embryonic web site: Marmorkrebs.org

Every journey begins with a first step. This journey begins with the creation of Marmorkrebs.org. This site is intended to be a clearing house and resource for the Marmorkrebs research community, and to evangelize this remarkable animal to the wider research community.

Since this is the very first post, I have to answer the logical question of what Marmokrebs is. "Marmorkrebs" roughly means "marbled crayfish" in German, and is the informal name for a species of crayfish that showed up in the European pet trade in the 1990s. The remarkable feature of this species is that it is parthenogenetic: all individuals are females, and they reproduce essentially by cloning themselves. While parthenogenesis is found in many species, Marmorkrebs is the only known decapod crustacean to do so. This method of reproduction makes Marmorkrebs a very attractive animal for laboratory research. Plus, their mysterious origin makes them intriguing study in their own right.

Currently, the Marmorkrebs.org page is in a very nascent form. It contains a micro FAQ (one question), and what may be a comprehensive bibliography of scientific research on Marmorkrebs. I hope this page will become much, much bigger and more substantive. And, I hope, prettier.

Pictured: a Marmorkrebs embryo. Appropriate, don't you think?