23 December 2014

Lessons from kiwis: “Conservation is all about killing things”

A New Yorker article starts off talking about killing an awful lot of rats on New Zealand, but makes its way to discussing invasive species more generally:

he project of reshuffling the world’s flora and fauna, which began slowly with the spread of species like the Pacific rat and sped up thanks to the efforts of acclimatization societies, has now, with global trade and travel, accelerated to the point that, on any given day, something like ten thousand species are being moved around just in the ballast water of supertankers.

The picture is of Nick Smith, NZ conservation minister, in one of the photo ops with dead rats described in the article.

Many conservation efforts around crayfish involve killing a lot of invasive crayfish. But it’s unlikely many magazine articles will be written about that.

External links

The big kill

Picture from here.

Hat tip to Mary Mangan.

18 December 2014

Celebrate diversity: speciation in the lab

One of the stock criticisms of evolution is that new species have never been seen to be created. There are plenty of examples, and one of the more recent was the creation of a new lizard species in the lab, back in 2011. I wrote a bit about about it before. At the time, it was not given a species name.

Now, a new paper by Cole and colleagues has come out on that species, and given it a new monicker, Aspidoscelis neavesi. This is a classic taxonomic paper, really, with lots of descriptions and diagnostic criteria and locations of type speciments. It is interesting in that it grapples with the question of how to deal with hybrid lineages in a taxonomic sense, which has also been a problem with Marmorkrebs.

Carl Zimmer reports on this, and talks a bit about the taxonomic puzzles:

Aspidoscelis neavesi also raises a special puzzle, Dr. Hillis noted, because it emerged over and over again. Dr. Baumann and his colleagues have now successfully produced fertile hybrids of Aspidoscelis inornata and Aspidoscelis exsanguis dozens of times from different parents. Since each lineage comes from different parents, they could arguably be considered separate species, not just a new one.


Cole CJ, Taylor HL, Baumann DP, Baumann P. 2014. Neaves' whiptail lizard: the first known tetraploid parthenogenetic tetrapod (Reptilia: Squamata: Teiidae). Breviora 539: 1-20. http://dx.doi.org/10.3099/MCZ17.1

External links

The Strange Tale of a New Species of Lizard
Related posts

Celebrate diversity: Instant whiptail!

04 December 2014

Keller and colleagues, 2014

Keller NS, Pfeiffer M, Roessink I, Schulz R, Schrimpf A. 2014. First evidence of crayfish plague agent in populations of the marbled crayfish (Procambarus fallax forma virginalis). Knowledge and Management of Aquatic Ecosystems 15: 8. http://dx.doi.org/10.1051/kmae/2014032


The introduction of non-indigenous species and associated diseases can cause declines in indigenous flora and fauna and threaten local biodiversity. The crayfish plague pathogen (Aphanomyces astaci), carried and transmitted by latent infected North American crayfish, can lead to high mortalities in indigenous European crayfish populations. Although the parthenogenetic marbled crayfish (Procambarus fallax (Hagen, 1870) forma virginalis) is common in the aquarium trade and has established wild populations in Europe, its carrier status is still unknown. This study investigated one captive and three established wild-living marbled crayfish populations for an infection with the crayfish plague pathogen applying real-time PCR. We demonstrate that captive, as well as two wild marbled crayfish populations were infected by A. astaci. Although infection status in laboratory kept specimens reached high levels, marbled crayfish showed no obviously plague-related mortality. Furthermore, sequence analysis revealed that captive crayfish carried the A. astaci genotype Pc, which has earlier been isolated from the North American red swamp crayfish (Procambarus clarkii). The results indicate that due to its positive carrier status marbled crayfish poses a greater threat to local biodiversity in Europe than considered until now.

Keywords: marbled crayfish • crayfish plague agent • exotic pathogen • invasive species • real-time PCR

02 December 2014

The colours, man, check out the colours...

These images I found on a Craigslist ad caught me attention as being a bit... brighter than most Marmorkrebs pictures I see.

I think there may be a little Instagram-style filtering going on...

19 November 2014

Patoka and colleagues, 2014

Patoka J, Kalous L, Kopecký O. 2014. Risk assessment of the crayfish pet trade based on data from the Czech Republic. Biological Invasions 16(12): 2489-2494. http://dx.doi.org/10.1007/s10530-014-0682-5


The pet trade in freshwater crustaceans, including crayfish, has grown rapidly in recent decades and become an important pathway for introducing new non-indigenous species into Europe. This paper provides the first overview of non-indigenous crayfish species (NICS) traded as ornamental and their potential impact in the Czech Republic, which is the second leading importer into Europe. The paper presents a full list of traded crayfish species, their market availability, and trade names or misnomers used in the country. In total, 27 crayfish species from all three families are advertised and marketed, of which Astacus astacus is the only indigenous species. Only three NICS were recognized as very common on the market. The invasiveness and risk associated with ornamental crayfish trade were assessed using the Freshwater Invertebrate Invasiveness Scoring Kit. Five NICS were classified into the high-risk category, the highest score being for Procambarus fallax f. virginalis. The invasiveness of crayfish indigenous to North America is significantly greater than that of crayfish from the rest of the world, and therefore regulation in this regard is recommended.

Keywords: Ornamental animal • Invasiveness • FI-ISK • Aquarium • Trade names

Chucholl, 2014

Chucholl C. 2014. Predicting the risk of introduction and establishment of an exotic aquarium animal in Europe: insights from one decade of Marmorkrebs (Crustacea, Astacida, Cambaridae) releases. Management of Biological Invasions 5(4): 309-318. http://dx.doi.org/10.3391/mbi.2014.5.4.01


The presence of the North American Marmorkrebs (Procambarus fallax f. virginalis) in European inland waters is entirely driven by ongoing propagule pressure from the ornamental trade. Since 2003 at least 25 independent introduction events have been confirmed, of which some have eventually resulted in established populations. This study links a maximum-entropy model that forecasts the probability of Marmorkrebs introduction based on socio-economic predictors to an updated species distribution model based on environmental predictors in order to explore the risk of further Marmorkrebs establishment in Europe. In line with related research, the probability of Marmorkrebs release was largely affected by gross domestic product and human population density, i.e. predictors very likely related to the density of Marmorkrebs owners, whereas environmental suitability was mostly influenced by minimum temperature and the availability of lentic habitats, which was indirectly assessed by terrain slope. While considerable parts of Europe were predicted as potentially suitable for establishment, high probabilities of introduction were forecasted in much smaller geographic areas. The consensus map of the model predictions suggests that introduction and subsequent establishment of Marmorkrebs is likely to occur in much of Germany, the Benelux countries, England, Italy, and areas of high human population density throughout France and Spain, as well as parts of southernmost Scandinavia and Southeastern Europe. Monitoring trades of Marmorkrebs in these high-risk regions is recommended and implications for proactive measures are discussed, including the need for consistent trade regulations at the EU level.

Keywords: marbled crayfish • propagule pressure • risk assessment • ornamental trade • introduction pathway

Celebrate diversity: Winning evolution without sex

Quanta magazine has a nice feature article on rotifers, which are apparently some of the longest running asexual lineages that we know about. Or maybe they’re not asexual... maybe it’s sex, Jim, but not as we know it:

The new work has shown bdelloids to be so good at generating genetic diversity that some researchers now question the very definition of sex, with some arguing for a more expansive one that doesn’t require the orchestrated swapping of genetic material. Others think that even if the traditional definition of sex remains intact, the unique genetic strategies of the bdelloid rotifer will illuminate the mechanisms that make sex such a successful evolutionary strategy.

11 November 2014

Vojkovská and colleagues, 2014

Vojkovská R, Horká I, Tricarico E, Duriš Z. 2014. New record of the parthenogenetic marbled crayfish Procambarus fallax f. virginalis from Italy. Crustaceana 87(11-12): 1386-1392. http://dx.doi.org/10.1163/15685403-00003365


To date, the ‘marbled crayfish’, Procambarus fallax (Hagen, 1870) f. virginalis, in Italy has been reported only from Tuscany (central Italy). Recently, specimens of this alien American crayfish were found in the Po di Maistra Channel, Porto Tolle, south of Venice (northern Italy). The identification of this species was confirmed by its external morphology and colour pattern, as well as by molecular analysis. The present report provides the second record for the marbled crayfish in Italy.

Keywords: None provided.

28 October 2014

Celebrate diversity: Big babies

The latest additions to “creatures we thought reproduced sexually but turn out to be able to reproduce asexually” is a pretty spectacular one, because one of the two species is one of the biggest snakes in the world.

A paper published back in June by Booth and colleagues is suddenly making the rounds on news and social media. It describes research on two python species, the reticulated python (pictured, record holder for longest snake), and the royal python. While the news is focusing on “snake gives virgin birth!” angle, this paper is far more interesting.

The major question in this paper is: how do animals switch, genetically, from sexual to asexual reproduction? In most vertebrates - including the two in this paper - the answer is “terminal fusion automixis.”

In most female vertebrates, gametes divide unevenly in meiosis, with one large cell set to become the egg, and the other becoming a “polar body,” which normally dies. Some species are able to take the polar body and have it act like a sperm cell. The offspring that result are not genetically identical to their mother, because there is a a random element in meiosis.

There’s been one apparent exception: a Burmese python reproduced without sex, and the offspring were clones of the mother. If so, the offspring could not have been generated by terminal fusion automixis. This would be weird, given that this is out of step with an increasingly large number of cases.

Booth and colleagues, however, describe some unpublished data from another Burmese python laying eggs without sex. Here, the offspring are apparently not clones of the mother, which is in line with other species, but not the one previous account. Because of this, Booth and company suggest the previous paper be “viewed cautiously.”

This would be the normal translation from academese:

Booth and colleagues suggest that the first clone python report is not due to an error. Instead, they suggest that an individual, which had been created by parthenogentic reproduction, reproduced again by the same means. They write:

If this is indeed the case, this would represent the first documentation of such reproductive competence of (facultative parthenogensis) in vertebrates.

Only time (and a few more replications) will tell if there are indeed clone snakes. If there are, they seem to be rare.

Hat tip to Jason Goldman.


Booth W, Schuett GW, Ridgway A, Buxton DW, Castoe TA, Bastone G, Bennett C, McMahan W. 2014. New insights on facultative parthenogenesis in pythons. Biological Journal of the Linnean Society 112(3): 461–468. http://onlinelibrary.wiley.com/doi/10.1111/bij.12286/full

External links

Virgin Birth Discovered In The World's Largest Snake
Python babies the result of 'virgin birth,' zoo confirms

Photo by Ryan Somma on Flickr; used under a Creative Commons license. Graffiti picture from here.

12 August 2014

Mestre and colleagues, 2013

Mestre A, Aguilar-Alberola JA, Baldry D, Balkis H, Ellis A, Gil-Delgado JA, Grabow K, Klobučar G, Kouba A, Maguire I, Martens A, Mülayim A, Rueda J, Scharf B, Soes M, S. Monrós J, Mesquita-Joanes F. 2013. Invasion biology in non-free-living species: interactions between abiotic (climatic) and biotic (host availability) factors in geographical space in crayfish commensals (Ostracoda, Entocytheridae). Ecology and Evolution 3(16): 5237–5253. http://dx.doi.org/10.1002/ece3.897


In invasion processes, both abiotic and biotic factors are considered essential, but the latter are usually disregarded when modeling the potential spread of exotic species. In the framework of set theory, interactions between biotic (B), abiotic (A), and movement-related (M) factors in the geographical space can be hypothesized with BAM diagrams and tested using ecological niche models (ENMs) to estimate A and B areas. The main aim of our survey was to evaluate the interactions between abiotic (climatic) and biotic (host availability) factors in geographical space for exotic symbionts (i.e., non-free-living species), using ENM techniques combined with a BAM framework and using exotic Entocytheridae (Ostracoda) found in Europe as model organisms. We carried out an extensive survey to evaluate the distribution of entocytherids hosted by crayfish in Europe by checking 94 European localities and 12 crayfish species. Both exotic entocytherid species found, Ankylocythere sinuosa and Uncinocythere occidentalis, were widely distributed in W Europe living on the exotic crayfish species Procambarus clarkii and Pacifastacus leniusculus, respectively. No entocytherids were observed in the remaining crayfish species. The suitable area for A. sinuosa was mainly restricted by its own limitations to minimum temperatures in W and N Europe and precipitation seasonality in circum-Mediterranean areas. Uncinocythere occidentalis was mostly restricted by host availability in circum-Mediterranean regions due to limitations of P. leniusculus to higher precipitation seasonality and maximum temperatures. The combination of ENMs with set theory allows studying the invasive biology of symbionts and provides clues about biogeographic barriers due to abiotic or biotic factors limiting the expansion of the symbiont in different regions of the invasive range. The relative importance of abiotic and biotic factors on geographical space can then be assessed and applied in conservation plans. This approach can also be implemented in other systems where the target species is closely interacting with other taxa.

Keywords: biological invasions • BAM diagrams • ecological niche models • host availability

Note: Co-author Menno Soes confirmed that the “Procambarus fallax” studied in this paper is indeed P. fallax f. virginalis, or Marmorkrebs.

First look at Freshwater Crayfish: A Global Overview

A new book on crayfish is now up at the publisher’s website. Here is the publisher’s description, with my emphasis added:


  • Provides an up-to-date reference work on commercially important crustaceans
  • Covers conservation status and biology of all endangered species, taxonomy, and distribution of crayfishes worldwide
  • Introduces a new model aquatic organism—a parthenogenetic freshwater crayfish


For their great commercial importance as a human food delicacy, crayfish are now becoming of wider interest to molecular biologists, and also to conservationists due to the fact that in some countries many of the native crayfish species are under threat from human activity, disease, and competition from other introduced crayfish species. Helmed by three editors in Japan, Europe, and the US, this book invites contributions from experts around the globe, covering the conservation status and biology of all endangered species, taxonomy, and distribution of crayfishes worldwide

It is slated for publication 15 April 2015.

04 August 2014

Verschueren, 2013

Verschueren H. 2013. Tracing endangered and invasive animal species in water using eDNA detection methods. Master’s thesis in Forensic Science: University of Amsterdam. http://dare.uva.nl/document/497579


In the Netherlands several protected animals that live in surface waters are monitored to meet Dutch directives or laws. Current animal monitoring is mainly based on visual observations which can be time consuming and labor intensive. These methods are also not always effective for animal species that are rare, have a hidden lifestyle or have ambiguous morphological characteristics. Alternative monitoring methods were introduced for animal species that live (partly) in water based on detection of DNA - traces excreted into the environment (eDNA). Due to the fact that this method detects DNA, it is not required to catch or even observe the target organisms. eDNA can be detected and quantified using quantitative polymerase chain reaction (qPCR). This project aimed to develop and validate eDNA detection methods for protected weatherfish (Misgurnus fossilis) and great crested newt (Triturus cristatus) species, and for seven invasive freshwater crayfish species (Astacidae & Cambaridae). Target species are selected because they are rare (T. cristatus and M. fossilis) or have a hidden lifestyle (all). Besides, early detection of exotic and invasive species (Astacidae & Cambaridae) is essential for success of a control plan. Furthermore was examined under which circumstances eDNA detection method provide better results. Finally, two different sample processing procedures were compared for DNA yields and detection probability.

eDNA detection methods require robust qPCR-protocols for amplification and quantification of target species DNA. Specific primers were developed targeting COI, CytB and 16S genes present on mitochondrial DNA. Mitochondrial DNA (mtDNA) is known for its high copy number which increases detection chance. Besides, these DNA regions are variable between species but conserved within species. Both properties make mtDNA a suitable target for species specific detection methods. Species specific qPCR-protocols were proposed after extensive in silico and in vitro analysis. Primers and probes were analyzed for amplification efficiency of target- and reference species DNA. Specific M. fossilis and T. cristatus assays were successfully developed targeting a region in the COI gene. Assays for invasive Astacidae & Cambaridae species were not successful yet.

The sensitivity of the methods was successfully determined by analyzing samples taken from locations where target species were present. Developed eDNA methods were validated in a field study. Twelve locations were sampled in triplicate at several water bodies in the Alblasserwaard polder during early spring and late spring. Results were compared to conventional screening data from the same period. In general M. fossilis and T. cristatus DNA was detected in all samples taken from locations where species were observed. Moreover, DNA was amplified in more samples if collected during late spring than during early spring. This is most likely due to inactive M. fossilis species or absent T. cristatus species during colder periods. Finally, two different sampling methods and procedures were applied: 1 L filtration versus 15 mL precipitation. Sample filtration results in extraction of merely cellular DNA while sample precipitation results in extraction of both cellular- and extracellular DNA. Comparison of the results slightly indicated that precipitation of 15 mL volumes give higher DNA yields and filtration of 1 L volumes give higher detection probability. In conclusion, eDNA detection methods designed for Misgunrus fossilis and Triturus cristatus species show potential to be sensitive and specific tools in species monitoring but more research is needed before it can be applied.

Keywords: None provided.

02 August 2014

van Oosterhout and colleagues, 2014

van Oosterhout F, Goitom E, Roessink I, Lürling M. 2014. Lanthanum from a modified clay used in eutrophication control is bioavailable to the marbled crayfish (Procambarus fallax f. virginalis). PLOS ONE 9(7): e102410. http://dx.doi.org/10.1371/journal.pone.0102410


To mitigate eutrophication in fresh standing waters the focus is on phosphorus (P) control, i.e. on P inflows to a lake as well as a lake’s sediment as internal P source. The in-lake application of the lanthanum (La) modified clays – i.e. La modified bentonite (Phoslock) or La modified kaolinite, aim at dephosphatising the water column and at reducing the release of P from a lake’s sediment. Application of these clays raises the question whether La from these clays can become bioavailable to biota. We investigated the bioavailability of La from Phoslock in a controlled parallel groups experiment in which we measured the La in carapace, gills, ovaries, hepatopancreas and abdominal muscle after 0, 14 and 28 days of exposure to Phoslock. Expressing the treatment effect as the difference of the median concentration between the two treatment groups (Phoslock minus control group) yield the following effects, the plus sign (+) indicating an increase, concentrations in µg g−1 dry weight: Day 14: carapace +10.5 µg g−1, gills +112 µg g−1, ovaries +2.6 µg g−1, hepatopancreas +32.9 µg g−1 and abodminal muscle +3.2 µg g−1. Day 28: carapace +17.9 µg g−1; gills +182 µg g−1; ovaries +2.2 µg g−1; hepatopancreas +41.9 µg g−1 and abodminal muscle +7.6 µg g−1, all effects were statistically significant. As La from Phoslock is bio-available to and taken up by the marbled crayfishes (Procambarus fallax f. virginalis), we advocate that the application of in-lake chemical water treatments to mitigate eutrophication should be accompanied by a thorough study on potential side effects.

Keywords: None provided.

25 June 2014

Kouba and colleagues, 2014

Kouba A, Petrusek A, Kozák P. 2014. Continental-wide distribution of crayfish species in Europe: update and maps. Knowledge and Management of Aquatic Ecosystems 413: 05. http://dx.doi.org/10.1051/kmae/2014007


Recently published astacological studies substantially improved available data on distribution of crayfish in various European regions. At the same time, spread of invasive species has been recorded, additional non-indigenous species became established in various countries, and losses of populations of native species due to crayfish plague and other negative factors were observed. We overview recent advances in this knowledge, and provide updated colour maps of the distribution of all crayfish species present in Europe. These maps are originally based on the data from the Atlas of Crayfish in Europe published in 2006 as a result of the CRAYNET project, and were further updated from more recently published reports, grey literature, and especially thanks to contributions and feedback of over 70 specialists from 32 countries. Separate maps are available for all indigenous crayfish species in Europe as well as for three most widespread non-indigenous crayfish species. Additionally, two maps give locations of known findings of crayfish species introduced to Europe after 1980. These newly established alien species have so far restricted distributions; however, the frequency of recent reports suggests that findings of such species resulting from releases of aquarium pets will further increase.

Keywords: crayfish distribution • indigenous species • invasive species • native range • maps

24 June 2014

Soedarini and colleagues, 2014

Soedarini B, van Gestel CAM, van Straalen NM, Widianarko B, Röling WFM. 2013. Interactions between accumulated copper, bacterial community structure and histamine levels in crayfish meat during storage. Journal of the Science of Food and Agriculture 94(10): 2023-2029. http://dx.doi.org/10.1002/jsfa.6519



Pollution in aquaculture areas may negatively impact edible species and threaten seafood quality and safety. The aim of this study was to determine the interaction between copper and bacteria in the aquatic habitat and their impact upon crustaceans. Marbled crayfish was chosen as a model of aquatic crustaceans and the influence of metal contamination on bacterial community structure in water used to culture crayfish and in crayfish themselves was investigated. Histamine, an allergen commonly formed by certain groups of bacteria in crustacean's edible tissue during storage, was also determined.


Copper exposure increased its concentration in crayfish meat by 17.4%, but the copper concentration remained within acceptable food safety limits. Elevated copper levels affected the bacterial community both in the water used to cultivate crayfish and in the marbled crayfish themselves. Cluster analysis of 16S rRNA-gene based microbial community fingerprints revealed that copper impacted the bacterial community in the water and in the crayfish meat. However, copper exposure reduced the formation of histamine in crayfish meat during storage by 66.3%.


Copper from the habitat appears to reduce histamine accumulation in crayfish meat during storage by affecting the bacterial community structure of the cultivation water and most likely also in the intestines of the crayfish. From a food safety point of view, copper treatment during the aqua culturing of crustaceans has a positive impact on the postharvest stage.

Keywords: copper • bacterial community structure • histamine • crayfish • storage

21 April 2014

Time to rename “crayfish” plague?

Marmorkrebs are potential vectors for crayfish plague, which is caused by Aphanomyces astaci. This pathogen devastated European crayfish since being introduced along with North American crayfish.

Now, we find out it’s not just crayfish that it can infect. A new paper by Svoboda and colleagues shows it can infect freshwater crabs, like the land crab Potamon potamios (pictured) and the Chinese mitten crab Eriocheir sinensis. The crabs appear to be more resistant to the infection than European crayfish, making the problem that the crabs are potential spreaders of disease than sufferers from it.

Hat tip to Tommy Leung.

Related post

Plague poster


Svoboda J, Strand DA, Vrålstad T, Grandjean F, Edsman L, Kozák P, Kouba A, Fristad RF, Bahadir Koca S, Petrusek A. 2014. The crayfish plague pathogen can infect freshwater-inhabiting crabs. Freshwater Biology 59:918-929.

Photo by Alastair Rae on Flickr; used under a Creative Commons license.

08 April 2014

Nefarious schemes!

Action! Adventure! Crayfish!

I always joke that the reason I went to grad school was so I could get a Ph.D., so I could be called “Doctor Zen” and sound like the villain from a bad kung fu movie.

Not a kung fu movie, but just as good.

Game designer John Wick is an acquittance of mine, who I connected with back in my grad school days. After I got my Ph.D., he took to calling me “the nefarious Doctor Zen.”

My evil namesake has been a recurring character in John’s role-playing projects (here and
there),but this is probably the biggest role yet. It includes this little bit:

The plan backfired, however, as the spider fought against Doctor Zen and his army of giant marmorkrebs (also known as marbled crayfish).

What villianous henchmen do I have now? Still very crustacean related... you will have to buy the game adventure to find out!

External links

Cartoon Action hour at Spectrum Games
Cartoon Action Hour core game
Cartoon Action Hour Season 3: Infinivaders!

01 January 2014

2013 was the second best year ever for Marmorkrebs research

Continuing an annual tradition here on the Marmorkrebs blog, we look back at what the year brought in Marmorkrebs research...

The increase in papers may be slow, but an increase it is. I like the trend...