31 May 2016

Kouba and colleagues, 2016

Kouba A, Tíkal J, Císar P, Veselý L, Fort M, Príborský J, Patoka J, Buric M. 2016. The significance of droughts for hyporheic dwellers: evidence from freshwater crayfish. Scientific Reports 6: 26569. http://dx.doi.org/10.1038/srep26569


Freshwater biodiversity is globally threatened by various factors while severe weather events like long-term droughts may be substantially devastating. In order to remain in contact with the water or stay in a sufficiently humid environment at drying localities, the ability to withstand desiccation by dwelling in the hyporheic zone, particularly through vertical burrowing is crucial. We assessed the ability of three European native and five non-native crayfish as models to survive and construct vertical burrows in a humid sandy-clayey substrate under a simulated one-week drought. Three native species (Astacus astacus, A. leptodactylus, and Austropotamobius torrentium) suffered extensive mortalities. Survival of non-native species was substantially higher while all specimens of Cherax destructor and Procambarus clarkii survived. The native species and Pacifastacus leniusculus exhibited no ability to construct vertical burrows. Procambarus fallax f. virginalis and P. clarkii constructed bigger and deeper burrows than C. destructor and Orconectes limosus. In the context of predicted weather fluctuations, the ability to withstand desiccation through constructing vertical burrows into the hyporheic zone under drought conditions might play a significant role in the success of particular crayfish species, as well as a wide range of further hyporheic-dwelling aquatic organisms in general.

Keywords: behavioural ecology • biodiversity • hydrology • limnology

03 May 2016

Lőkkös and colleagues, 2016

Lőkkös A, Müller T, Kovács K, Várkonyi L, Specziár A, Martin P. 2016. The alien, parthenogenetic marbled crayfish (Decapoda: Cambaridae) is entering Kis-Balaton (Hungary), one of Europe’s most important wetland biotopes. Knowledge and Management of Aquatic Ecosystems 417: 16. http://dx.doi.org/10.1051/kmae/2016003


The marbled crayfish or Marmorkrebs, Procambarus fallax (Hagen, 1870) f. virginalis, a parthenogenetic freshwater crayfish belonging to the North American cambarids, was recorded in Hungary for the first time. Several specimens of this potentially invasive crayfish were caught at different locations in the thermal Lake Hévíz and its outflows in the western part of the country. Captured individuals covered a wide size range (5.5 to 50.5 mm carapace length) and one was carrying eggs and recently hatched offspring, which suggests that this organism has established a stable and self-sustaining population in the warm habitats of Lake Hévíz area. This finding is of great significance because these habitats belong to the catchment of the Danube River including Lake Balaton, and thus, a significant further spread of the marbled crayfish is likely to happen in Central Europe. Furthermore, the expansion of this crayfish already reached the Kis-Balaton, one of the landscape protection areas of the Balaton Uplands National Park, what could have currently yet unpredictable consequences for this unique wetland biotope.

Keywords: non-indigenous crayfish species • pet trade • illegal release • crayfish plague • thermal lake

Note: One of the latitude and longitude coordinates in Table 2 is incorrect. The coordinates for Lake Hévíz should be N 46° 47.252', E 17° 11.501'. The corresponding author confirmed this.

02 May 2016

African crayfish

The Conversation hosts a good post by Ana Nunes about the introduction of crayfish into Africa. Marmorkrebs make a brief cameo appearance (with an incomplete name):

Another species that bears mentioning is the marbled crayfish or “Marmokrebs” (Procambarus fallax) (sic). It was introduced to Madagascar for mysterious reasons, but there may be a link with a road building project carried out by foreign contractors in 2003/2004. In 2005, biologists at the University of Antananarivo noticed it being sold in markets close to the capital.

This particular crayfish has a peculiar history: nobody knows where it comes from. It simply appeared in the German aquarium trade in about 1995. It is also the only decapod in the world known to be able to reproduce by parthenogenesis – a female is able to reproduce without being fertilised by a male. This means that a single individual is sufficient to start a whole new population. As such, this species seems very likely to pose a serious threat to freshwater biodiversity in Madagascar.

Even though it focuses on one continent, it is a very nice lay summary of the issues around crayfish introductions.

External links

Freshwater crayfish: the forgotten invaders wreaking havoc across Africa

Pictured: Lake Naivasha, site of a Procambarus clarkii introduction. Picture from here.