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