Laurenz and colleagues 2020

Laurenz J, Georg A, Brendelberger H, Lehmann K. 2020. Effects of nitrate on early life stages of Astacus astacus (Linnaeus, 1758) and Procambarus virginalis (Lyko, 2017). International Aquatic Research 12(1): 53-62. https://doi.org/10.22034/iar(20).2020.671232

Abstract

We examined the effects of nitrate on the embryonic development of two freshwater crayfish species, the indigenous noble crayfish (Astacus astacus) and the invasive marbled crayfish (Procambarus virginalis). Nitrate measurements show concentrations of 50 mg/L in surface waters of Germany, while concentrations in groundwater measure up to 100 mg/L. Performing a chronic exposure experiment, we exposed embryos of both species to nitrate concentrations of between 0.0 mg/L and 500 mg/L to estimate the influences of nitrate concentrations on survival, hatching development time, malformations and growth. We observed the first effects on survival at 14 mg/L LOEC (lowest observed effective concentration) nitrate for marbled crayfish. For noble crayfish, we estimated an EC50 value of 55.7 mg/L on hatching rate. Our results show that eutrophication of surface waters can negatively affect the embryonic development of freshwater crayfish with serious consequences on recruitment.

Keywords: marbled crayfish • noble crayfish • juveniles • nitrate • embryonic

Michigan considering prohibiting Marmorkrebs

Yesterday, there was a conference call meeting of the Michigan Natural Resources Commission that included discussion of adding Marmorkrebs to the state’s list of invasive species.

The presentation slide deck makes some... interesting statements.

Slide 14 in the deck says, “No native range, presumed product of captive breeding”. This implies that someone deliberately set out to create an asexual crayfish, and that’s misleading at best. There is zero evidence I am aware of that anyone deliberately set out to create an asexual crayfish. Marmorkrebs may have originated in captivity, but nobody planned it. Nobody thought an asexual crayfish was even possible. Nobody was “breeding” for it

Slide 15 says, “Threat to natural resources: Aggressive behavior traits”. This is an odd item to list first. There is no evidence that Marmorkrebs are more aggressive than other crayfish species. The papers on Marmorkrebs fighting to date have shown that they are competitive in when they are facing size-matched individuals from other species. The qualifier is important, because Marmokrebs are smallish crayfish. Many other species get larger, and large animals win. Further, Marmorkrebs have only been compared with a couple of other crayfish species.

The same slide lists another threat as “Introduce disease”. Maybe? Disease has been a big problem with introduced crayfish in Europe, but last I looked at a map, Michigan is not Europe. In the US, disease has usually not been a significant problem with crayfish impacts. It could be. But so far, this seems like one of the lower risks.

I would have inverted this list, and started with “Alter fish communities” and “Degrade water quality”.

The bottom line? The slide deck lists the “next steps” as:

• Recommend listing Marbled Crayfish as prohibited to DNR-Director
• Officially list in May, if recommendation is approved

So this process looks quite advanced and likely to happen.

If this went through, this would make Michgan the third North American jurisdiction to regulate Marmorkrebs specifically.

External links

16 April 2020 agenda of Natural Resource Commission (PDF)
Presentations given to the NRC - 16 April 2020, Fish (PDF)

Join in this week’s NRC meeting online or by conference call

Andriantsoa and colleagues, 2020

Andriantsoa R, Jones JPG, Achimescu V, Randrianarison H, Raselimanana M, Andriatsitohaina M, Rasamy J, Lyko F. 2020. Perceived socio-economic impacts of the marbled crayfish invasion in Madagascar. PLOS ONE 15(4): e0231773. https://doi.org/10.1371/journal.pone.0231773

Abstract
The negative environmental and economic impacts of many invasive species are well known. However, given the increased homogenization of global biota, and the difficulty of eradicating species once established, a balanced approach to considering the impacts of invasive species is needed. The marbled crayfish (Procambarus virginalis) is a parthenogenetic freshwater crayfish that was first observed in Madagascar around 2005 and has spread rapidly. We present the results of a socio-economic survey (n = 385) in three regions of Madagascar that vary in terms of when the marbled crayfish first arrived. Respondents generally considered marbled crayfish to have a negative impact on rice agriculture and fishing, however the animals were seen as making a positive contribution to household economy and food security. Regression modeling showed that respondents in regions with longer experience of marbled crayfish have more positive perceptions. Unsurprisingly, considering the perception that crayfish negatively impact rice agriculture, those not involved in crayfish harvesting and trading had more negative views towards the crayfish than those involved in crayfish-related activities. Food preference ranking and market surveys revealed the acceptance of marbled crayfish as a cheap source of animal protein; a clear positive in a country with widespread malnutrition. While data on biodiversity impacts of the marbled crayfish invasion in Madagascar are still completely lacking, this study provides insight into the socio-economic impacts of the dramatic spread of this unique invasive species. “Biby kely tsy fantam-piaviana, mahavelona fianakaviana” (a small animal coming from who knows where which supports the needs of the family). Government worker Analamanga, Madagascar.

Keywords: None provided.

Note: Co-author Julia Jones provides a summary of this paper and some personal commentary in a Twitter thread. Excerpt:

Fozaorana (Procambarus virginalis to give them their scientific name) became synonymous in Malagasy with something cheap and poor quality. Cheap burner phones are called fozaorana for example. ... (O)ur recent paper shows that (especially in areas which have been invaded longer), people tend to quite appreciate the crayfish & feel they make a positive impact in food security and livelihoods.

Coronavirus cancels crayfish conference

This year’s International Association of Astacology conference is not happening, due to COVID-19 concerns. The next meeting is scheduled for 2021.

(I should say, “tentatively scheduled,” since we don’t know how long this pandemic is going to go on.)

Commerical eDNA testing for Marmorkrebs

The English company SureScreen Scientifics is offering commercial environmental DNA (eDNA) testing for the detection of Marmorkrebs. This is, as far as I am aware, the first commercial product or service that is specifically designed around Marmorkrebs, besides the sale of animals.

The rationale and context for this service is very much geared to monitoring white-clawed crayfish (Austropotamobius pallipes) populations in the UK.

The white-clawed crayfish is the only native crayfish species in the UK. It is endangered and under threat from invasive crayfish species such as signal crayfish and the crayfish plague. Our simple to use eDNA test provides a cost-effective opportunity to monitor these species.

The company’s main web page says they use eDNA to check for:

• White-clawed crayfish (Austropotamobius pallipes)
• Signal crayfish (Pacifastacus leniusculus)
• Marbled crayfish (Procambarus virginalis)
• Crayfish plague (Aphanomyces astaci)

The company’s technical white paper (PDF here) say they can also test for Lousiana red swamp crayfish (Procambarus clarkii) and two European species, narrow-clawed crayfish (Astacus leptodactylus) and noble crayfish (Astacus astacus). It’s not clear why these other three species are not listed on the main web page.

The ability to test for Marmorkrebs (and highlighting this on the main web page) is interesting, because there are no confirmed introductions of Marmorkrebs in the islands of Great Britain or Ireland.

On the other hand, the other four crayfish species that the company can tests for (P. leniusculus, P. clarkii, A. leptodactylus, and A. astacus) are already established in the UK (Peay et al. 2010). So are two other species, the virile crayfish (Faxonius limosus) and spiny-cheeked crayfish (Faxonius limosus) are also already in the UK.

I think there’s an interesting question of which should be the priority in developing a test: for the Faxonius species that we already know are there, or for species like Marmorkrebs that could be lurking there, undetected.

While the company is based in England, and is clearly attempting to fill a need for monitoring UK waterways, there is no reason I could see that they couldn’t handle samples from anywhere in the world.

By the way, nobody at SureScreen Scientifics paid me to say this.

References

Peay S, Holdich DM, Brickland J. 2010. Risk assessments of non-indigenous crayfish in Great Britain. Freshwater Crayfish 17: 109-122. http://iz.carnegiemnh.org/crayfish/iaa/fc17_toc.htm#


External links

SureScreen Scientific crayfish page

Mad about Marmorkrebs (mad angry, not mad interested)

A question on Quora popped up: “If Wikipedia is correct, how can people believe the speciation story of the Marbled Cray actually occurred?” I summarized the available science, which prompted this fascinating comment.

That the MC’ has 3 chromosomes, because it had 3 chromosomes when the scientists, (or whoever claimed a speciation occurred), (Your buddies), went to the German village, collected some live MC’s, thereon the person ‘creating’ the sham event, did put baby MC’s into the tank with Slough Cray’s……

It is obvious that Wiki are driven by Evolutionists like yourself, and writing a paper on how your mates say the sham speciation event occurred, is of no consequence to the reality that: The MC was ‘Created” a very long time ago with 3 chromosomes to be capable of self replication, to help feed the people, the German Traders at the Village has already stated to the world, that they were trading the MC’ for generations, hence, the MC’ simply has, and always had 3 chromosomes….

And your “Manufactured” series of events, are simply a stab in the dark, because the MC’ was placed in the tank, and people like you, then Peddle the sales pitch……… That is the TRUTH is it not

The internet is wonderful, because it lets you know what people think.

External links

If Wikipedia is correct, how can people believe the speciation story of the Marbled Cray actually occurred?

Maple leaf Marmorkrebs in the future?

The newest issue of Crayfish News from the International Association of Astacology features a nice little article by Premek Hamr on Canadian crayfish, which briefly mentions Marmorkrebs.

(T)wo additional species are likely to expand into Canada in the near future. The marbled crayfish (Procambarus virginalis) is a parthenogenetic species which originated from the German aquarium pet trade and has established in the wild in several European countries as well as Madagascar (Vogt, 2018). It is for sale in Canada from some pet dealers as well as private aquarists over the internet. Single and multiple specimens are available for sale for prices ranging between 1 and 15 CAD (Hamr, unpublished data). Since it survives in the wild in central Europe, it is very likely to escape and establish wild populations in the warmer parts of Canada such as Southern Ontario and coastal British Columbia. So far, it has not been documented in the wild in Canada to date but a release appears to be imminent (Hamr, unpublished data).

Imminent? Maybe. I agree that it will probably happen. But having tracked Marmorkrebs introductions for some years now, I have been surprised that there were not confirmed introductions and established populations in North America years ago now.

For some data on the trade in crayfish in Canada, see this paper.

References

Hamr P. 2020. The classification, status and distribution of Canadian crayfishes: an update. Crayfish News 42(1): 1, 3-5.

External links

Crayfish News archive