26 April 2011

Looking for hope

ResearchBlogging.orgWhen I went to the International Association for Astacology meeting last year, the first couple of days were largely concerned with crayfish as invasive species. The phrase that kept kept popping into my head was, “horror show.”

A new review article taps into that concern, asking flat out, “Is there a hope?” in the title. Note the use of the singular. Things are so bad, we are just looking for one hope.

Marmorkrebs make a brief cameo appearance in the paper:

Today, it is extremely easy to buy, via aquarium trade fairs and internet sales, NICS for ornamental use, as shown in the case of both the marbled crayfish (Nonnis Marzano et al. 2009; Peay 2009), a North American species recently identified as a parthenogenetic form of Procambarus fallax (Martin et al. 2010), and the Australian red-claw crayfish C. quadricarinatus in the UK (Peay 2009).

This is in section discussing the prospects for preventing invasive crayfish from becoming established. The laws are inconsistent and many proposed policies have never been implemented.

The bulk of the paper focuses on prospects for managing crayfish that have been already been introduced (with a convenient summary in Table 1). One of the surprises is that control by predators is more promising than I would have expected. For instance, eels have some attractive features – they don’t breed in fresh waters, so may not establish new populations, and they can get into crayfish burrows. Eels may not eat enough crayfish to keep the populations down, however.

The section on “Autocidal methods” shows, without the authors intending to do so, why Marmorkrebs could be such a challenge as an introduced species. These control techniques are based around “swamping” a population with sterile males, or using sex pheremones. But the common factor in both is sex... which Marmorkrebs don’t bother with. So a suite of promising management tools for other crayfish are highly unlikely to make a scratch in an introduced Marmorkrebs population.

In the end, the authors do see hope, but I think their last sentence is telling, because they find hope in the exotic crayfish situation not just in the science, but in science and education. This endeavour is not going to work is non-professionals (hobbyists, anglers, etc.) getting involved.


Gherardi F, Aquiloni L, DiƩguez-Uribeondo J, Tricarico E. 2011. Managing invasive crayfish: is there a hope? Aquatic Sciences 73(2): 185-200. DOI: 10.1007/s00027-011-0181-z

Photo by Gregory Moine on Flickr; used under a Creative Commons license.

19 April 2011

Marmorkrebs on the road: The Crustacean Society, Summer Meeting 2011

I’m planning on attending the summer meeting of The Crustacean Society in about a month and a half. I’ll be participating in a symposium organized by Brian Tsukimura on invasive species. From the sounds of things, I may be the only participant in the symposium discussing freshwater invasive species.

12 April 2011

Rubach and colleagues, 2011

Rubach M, Crum S, Van den Brink P. 2011. Variability in the dynamics of mortality and immobility responses of freshwater arthropods exposed to chlorpyrifos. Archives of Environmental Contamination and Toxicology 60(4): 708-721. http://dx.doi.org/10.1007/s00244-010-9582-6


The species sensitivity distribution (SSD) concept is an important probabilistic tool for environmental risk assessment (ERA) and accounts for differences in species sensitivity to different chemicals. The SSD model assumes that the sensitivity of the species included is randomly distributed. If this assumption is violated, indicator values, such as the 50% hazardous concentration, can potentially change dramatically. Fundamental research, however, has discovered and described specific mechanisms and factors influencing toxicity and sensitivity for several model species and chemical combinations. Further knowledge on how these mechanisms and factors relate to toxicologic standard end points would be beneficial for ERA. For instance, little is known about how the processes of toxicity relate to the dynamics of standard toxicity end points and how these may vary across species. In this article, we discuss the relevance of immobilization and mortality as end points for effects of the organophosphate insecticide chlorpyrifos on 14 freshwater arthropods in the context of ERA. For this, we compared the differences in response dynamics during 96 h of exposure with the two end points across species using dose response models and SSDs. The investigated freshwater arthropods vary less in their immobility than in their mortality response. However, differences in observed immobility and mortality were surprisingly large for some species even after 96 h of exposure. As expected immobility was consistently the more sensitive end point and less variable across the tested species and may therefore be considered as the relevant end point for population of SSDs and ERA, although an immobile animal may still potentially recover. This is even more relevant because an immobile animal is unlikely to survive for long periods under field conditions. This and other such considerations relevant to the decision-making process for a particular end point are discussed.

Keywords: None provided.

05 April 2011

Big finish

I’m all blogged out this week. Here are a few cute crayfish videos to keep you company.

An interesting little idea to create lots of “hidey holes” for juveniles.

I’ve kept crayfish in my lab for quite a while now, but have rarely caught them in the act of getting rid of their skeleton.

Big finish in the last 20 second or so of this one!