29 November 2015

Vogt, 2014

Vogt G. 2014. Life span, early life stage protection, mortality and senescence in freshwater Decapoda. In: Yeo DCJ, Cumberlidge N, Klaus S (eds.), Advances in Freshwater Decapod Systematics and Biology (Crustaceana Monographs 19), pp. 17-51. Brill: Leiden. http://www.brill.com/products/book/advances-freshwater-decapod-systematics-and-biology


This article review the present knowledge on ageing and longevity in the freshwater Decapoda and examines the impact of abbreviated development and postembryonic brood care, two major adaptations to fresh water, on life expectancy. Life span data are available for only 4% of freshwater decapods. Reliably determined maximum life spans in freshwater shrimps, crayfish, crabs, and aeglids vary from 8 months to 38 years and may be underestimated in slow-growing species. Decapods that live at high latitudes and high altitudes tend to live longer, which may reflect life history adaptations to cool water temperatures. Particularly long-lived species are found among crayfish and in subterranean habitats. Abbreviated and direct development and postembryonic brood care reduce mortality of the early life stages of freshwater decapods and are associated with an increase of individual life expectancy but the longevity of freshwater decapod species is not extended when compared to marine decapods. Long-lived freshwater decapods maintain structural and functional integrity into old age and possess several effective anti-ageing mechanisms including life-long stem cell activity. The most obvious anti-ageing mechanisms are moulting and the regeneration of damaged appendages, both of which obviate mechanical senescence. Some species of freshwater decapods are suitable models for the investigation of general topics of biogerontology.

Keywords: None provided.

24 November 2015

Veselý and colleagues, 2015

Veselý L, Buřič M, Kouba A. 2015. Hardy exotics species in temperate zone: can “warm water” crayfish invaders establish regardless of low temperatures? Scientific Reports 5: 16340. http://dx.doi.org/10.1038/srep16340


The spreading of new crayfish species poses a serious risk for freshwater ecosystems; because they are omnivores they influence more than one level in the trophic chain and they represent a significant part of the benthic biomass. Both the environmental change through global warming and the expansion of the pet trade increase the possibilities of their spreading. We investigated the potential of four “warm water” highly invasive crayfish species to overwinter in the temperate zone, so as to predict whether these species pose a risk for European freshwaters. We used 15 specimens of each of the following species: the red swamp crayfish (Procambarus clarkii), the marbled crayfish (Procambarus fallax f. virginalis), the yabby (Cherax destructor), and the redclaw (Cherax quadricarinatus). Specimens were acclimatized and kept for 6.5 months at temperatures simulating the winter temperature regime of European temperate zone lentic ecosystems. We conclude that the red swamp crayfish, marbled crayfish and yabby have the ability to withstand low winter temperatures relevant for lentic habitats in the European temperate zone, making them a serious invasive threat to freshwater ecosystems.

Keywords: ecology • invasive species

17 November 2015

Funkhauser, 2014

Funkhouser M. 2014. The toxicological effects of perfluorooctane sulfonate (PFOS) on a freshwater gastropod, Physa pomilia, and a parthenogenetic decapod, Procambarus fallax f. virginalis. Master's thesis, Environmental Toxicology, Texas Tech University. 102 pp. http://hdl.handle.net/2346/58533


Perfluorinated compounds (PFCs) are a class of synthetic chemicals that have recently become of increased interest and concern due to their ability to biomagnify through food webs. Perfluorinated compounds, in general, are persistent in the environment and some are carcinogenic. One specific PFC, perflurooctane sulfonate (PFOS), has gained increased attention because it is slightly toxic to aquatic organisms and has been detected in tissues of a wide variety of animals from all over the world including remote species such as polar bears. Like other PFCs, PFOS is highly resistant to chemical, biological, and thermal breakdown, and has high water solubility and low volatility; all of which indicate that PFOS can be both mobile and persistent in the environment. Like many PFAAs, PFOS was a key ingredient in Aqueous Film Forming Foams (AFFF) to fight hydrocarbon-fueled fires on fire-fighting training facilities common to airports and air force bases. Despite the fact that PFCs like PFOS have been detected in many habitats, the fate, biotransport mechanism, and overall ecotoxicology of PFCs are highly uncertain. While there are some data on environmental concentrations and toxicity to organisms, there is a general lack of toxicity data for many aquatic taxa. Despite initial heavy use on U.S. Air Force Bases, there is now growing concern of PFCs as they emerge as important contaminants on a global scale, especially at Barksdale Air Force Base (BAFB) in Shreveport, Louisiana. Of particular concern is whether PFCs from BAFB have now entered surface water and, if so, whether concentrations are high enough to potentially cause human or ecological effects. The research presented here is part of a larger project to develop and implement a comprehensive approach for characterizing PFC contamination and estimating potential human and ecological risk focused on BAFB. The specific research presented here focused on further characterizing the toxicity of PFOS to several aquatic organisms, which represent taxa observed at BAFB. The goal was to determine dose-response relationships as well as species sensitivity to PFOS to ultimately support upcoming environmental risk assessments. Specifically, we conducted acute and chronic (full life cycle) toxicity tests to a model freshwater gastropod (Physa pomilia) and acute and sub-chronic toxicity tests to a new model organism, the marbled crayfish. Physa pomilia are excellent laboratory organisms and can make up a large portion of biomass in the aquatic ecosystem. Like many freshwater gastropods, this species can be readily collected from local habitats, has a short generation time, and is relatively easy to culture in the lab. We conducted several experiments to characterize toxicity of PFOS to P. pomilia including (1) a 96-hour acute toxicity study on adults, (2) a sub-chronic toxicity study on adults, (3) a full-life cycle study, and (4) a behavioral assay. Next, we characterized PFOS toxicity to the marbled crayfish, Procambarus fallax f. virginalis, which is a subspecies of Procambarus fallax. The marmorkreb (sic) is unique because it is the first known parthenogenetic decapod; offspring produced by individuals are genetically identical. To determine PFOS toxicity to the marmorkreb (sic) we conducted several studies that included (1) an acute juvenile study, (2) a sub-chronic juvenile study, and (3) a juvenile study in which animals were raised under two different densities. The last study was performed because the role of social interaction among crayfish is important due to their display of aggression toward conspecifics. The specific goals for this laboratory project on Physa pomilia and Procambarus fallax f. virginalis were to characterize the ecotoxicity of PFOS in two species that represent environmentally relevant taxa. Because the overall toxicity of PFOS varies considerably among taxa, our hope was to add toxicity data that could then be used to build an updated species sensitivity distribution (SSD) to inform future ecological risk assessments.

Keywords: None provided.

16 November 2015

Vogt and colleagues, 2015b

Vogt G, Falckenhayn C, Schrimpf A, Schmid K, Hanna K, Panteleit J, Helm M, Schulz R, Lyko F. 2015. The marbled crayfish as a paradigm for saltational speciation by autopolyploidy and parthenogenesis in animals. Biology Open 4(11): 1583-1594. http://dx.doi.org/10.1242/bio.014241


The parthenogenetic all-female marbled crayfish is a novel research model and potent invader of freshwater ecosystems. It is a triploid descendant of the sexually reproducing slough crayfish, Procambarus fallax, but its taxonomic status has remained unsettled. By cross-breeding experiments and parentage analysis we show here that marbled crayfish and P. fallax are reproductively separated. Both crayfish copulate readily, suggesting that the reproductive barrier is set at the cytogenetic rather than the behavioural level. Analysis of complete mitochondrial genomes of marbled crayfish from laboratory lineages and wild populations demonstrates genetic identity and indicates a single origin. Flow cytometric comparison of DNA contents of haemocytes and analysis of nuclear microsatellite loci confirm triploidy and suggest autopolyploidisation as its cause. Global DNA methylation is significantly reduced in marbled crayfish implying the involvement of molecular epigenetic mechanisms in its origination. Morphologically, both crayfish are very similar but growth and fecundity are considerably larger in marbled crayfish, making it a different animal with superior fitness. These data and the high probability of a divergent future evolution of the marbled crayfish and P. fallax clusters suggest that marbled crayfish should be considered as an independent asexual species. Our findings also establish the P. fallax–marbled crayfish pair as a novel paradigm for rare chromosomal speciation by autopolyploidy and parthenogenesis in animals and for saltational evolution in general.

Keywords: marbled crayfish • autopolyploidy • parthenogenesis • epigenetics • chromosomal speciation • saltational evolution

Note: This is the final version of record of this paper, which was previously available as a pre-print.

03 November 2015

“Millions of animals from a single specimen”

The forthcoming Biology Open paper on the speciation of Marmorkrebs continues to attract attention, with a very nice article on Medical XPress. It focuses on the prospects of using Marmorkrebs to study epigenetics, but includes the basic biology too:

Günter Vogt, a zoologist at Heidelberg University suggested that the DKFZ scientists take a look at the freshwater marbled crayfish which has now spread worldwide. In Madagascar, it reproduces so quickly that it poses a threat not just ecologically but also economically as the animals destroy rice crops. Marbled crayfish also occur in the lakes of southern Germany as well as in Sweden and Japan and are now even readily available in most aquarium and pet stores.

“As there are only females, I suspected that these crayfish might reproduce by cloning. If so, then these animals should all have identical DNA and the large variety in appearance and behaviour might be based entirely on epigenetic causes.”

Lyko was curious and started looking at these animals in the lab which confirmed the assumption. “We examined the DNA of 4 animals and found that they were completely identical, we did not detect a single genetic difference. The marbled crayfish is indeed a clone - millions of animals derive from a single original specimen.”