29 August 2017

Benson and colleagues, 2017

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


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

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

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

Keywords: None provided.

11 August 2017

I got 669 names, and Marmorkrebs ain’t one

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

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

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

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

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

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

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

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


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

10 August 2017

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


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

05 August 2017

The Lausanne Resolution turns 30

Today marks the 30th 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.

7th 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.


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

02 August 2017

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


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).

01 August 2017

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


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.