23 January 2020

Velisek and colleagues, 2020

Velisek J, Stara A, Kubec J, Zuskova E, Buric M, Kouba A. 2020. Effects of metazachlor and its major metabolite metazachlor OA on early life stages of marbled crayfish. Scientific Reports 10(1): 875. https://doi.org/10.1038/s41598-020-57740-1


The effects of the herbicide metazachlor and its major metabolite metazachlor OA at two concentrations, including environmentally relevant concentrations of metazachlor (0.0115 µmol/l and 0.0790 µmol/l) and metazachlor OA (0.0117 µmol/l and 0.0805 µmol/l), respectively, were evaluated on early ontogeny, growth, behaviour, oxidative stress, antioxidant enzyme levels, histology, and mortality of marbled crayfish Procambarus virginalis. Both tested concentrations of metazachlor and metazachlor OA were associated with significantly lower growth and delayed ontogenetic development compared to controls. Exposure of metazachlor at 0.0115 µmol/l and metazachlor OA at 0.0117 µmol/l and 0.0805 µmol/l resulted in significantly lower activity of total superoxide dismutase (SOD), catalase (CAT), glutathione s-transferase (GST), glutathione reductase (GR), and reduced glutathione (GSH) compared with control and resulted in gill anomalies ranging from wall thinning to focal disintegration of branchial structure. Metazachlor at the environmentally relevant concentration of 0.0790 µmol/l was associated with significant alterations of crayfish distance moved and walking speed. The potential risk associated with metazachlor use in agriculture related to effects on non-target aquatic organisms.

Keywords: None provided.

21 January 2020

Vogt, 2020

Vogt G. 2020. Biology, ecology, evolution, systematics and utilization of the parthenogenetic marbled crayfish, Procambarus virginalis. In: Ribeiro FB (ed.), Crayfish: Evolution, Habitat and Conservation Strategies, pp. 137-227. Nova Publishers: Hauppauge. https://novapublishers.com/shop/crayfish-evolution-habitat-and-conservation-strategies/


The marbled crayfish, Procambarus virginalis, is the only obligately parthenogenetic species of the 15,000 decapod crustaceans. This chapter describes its detection history, biology, taxonomy, geographical distribution, ecology, evolution and utilization. The marbled crayfish was detected in 1995 in the German aquarium trade. Morphological and genetic evidence suggests that it has arisen by autotriploidy from slough crayfish, Procambarus fallax, which is native to Florida and southern Georgia. Since marbled crayfish was neither described in the extensive biogeographical literature on crayfishs of this region nor found in respective museum collections it is thought to have originated in evolutionarily recent times, perhaps in captivity. Genetic investigations revealed that marbled crayfish is of single origin and monoclonal. Comparison of morphology, life history, genetics, reproduction, behavior, ecology and biogeography between marbled crayfish and its parent species and application of the Evolutionary Genetic Species Concept for Asexuals suggests treating marbled crayfish as a separate species rather than keeping it as a parthenogenetic lineage within Procambarus fallax. Beginning in the late 1990s, marbled crayfish was spread from Germany across the world. Releases have led to the establishment of wild populations in 16 countries on three continents. In Madagascar, marbled crayfish has already invaded a considerable proportion of the country. Behavioral and ecological data suggest that marbled crayfish can compete with other crayfish species, even with much bigger ones. Despite of genetic uniformity, marbled crayfish have adapted to a wide range of habitats in tropical to cold-temperate biomes. This was apparently possible by their capability to produce different phenotypes from the same genome by epigenetic mechanisms. Because of genetic identity, high fecundity, easy rearing, the availability of a draft genome and further advantages, the marbled crayfish is increasingly being used as a laboratory model for research including development, neurobiology, behavior, reproduction, toxicology, stem cell biology, genetics, epigenetics, and invasion biology. In Madagascar, wild marbled crayfish stocks are exploited as a food commodity.

Keywords: biogeography • competition • ecology • evolution • invasion • marbled crayfish • parthenogenesis • research model • systematics • exploitation

14 January 2020

Vogt, 2019

Vogt G. 2019. Estimating the young evolutionary age of marbled crayfish from museum samples. Journal of Natural History 53(39–40): 2353–2363. https://doi.org/10.1080/00222933.2019.1702730


The obligately parthenogenetic, all-female marbled crayfish, Procambarus virginalis, is a triploid descendant of the similarly looking, sexually reproducing slough crayfish, Procambarus fallax, native to Florida and southern Georgia. We have earlier hypothesised that marbled crayfish may have originated from P. fallax only some 25 years ago, perhaps in captivity. In order to investigate the young evolutionary age hypothesis in more detail, I searched the P. fallax collection of the Smithsonian Institution Museum of Natural History (USNM, Washington, D.C.) for evidence of marbled crayfish before its detection in the German aquarium trade in 1995. In particular, I analysed the sex ratio of P. fallax and the frequency of pure female samples throughout its entire distribution range to detect potentially misidentified marbled crayfish among the P. fallax. If marbled crayfish had originated from P. fallax long ago, spread throughout Florida and Georgia and erroneously been sampled as P. fallax, then the sex ratio of the P. fallax in the collection should be significantly biased towards females and pure female samples should be much more frequent than in related Procambarus species. Comparison of P. fallax (n = 2299) with its closest relatives P. seminolae (n = 801) and P. leonensis (n = 150) revealed female proportions of 55.33%, 53.93% and 54.67%, respectively, which are not significantly different from each other. The average female proportion of the 14 Procambarus species investigated (8641 specimens) was 52.54 ± 7.54% (mean ± standard deviation). Moreover, pure female samples consisting of more than 3 specimens that could represent hidden marbled crayfish were not conspicuously more common in P. fallax (2.33%) than in all Procambarus species investigated (1.24 ± 1.79%). These data suggest that the P. fallax collection of the USNM consists of real, sexually reproducing P. fallax and does most likely not include hidden marbled crayfish, supporting the young evolutionary age hypothesis for marbled crayfish.

Keywords: Marbled crayfish • evolution • Procambarus • museum collection • sex ratio

06 January 2020

2019 was the second best year ever for Marmorkrebs research

I am a little late, but the tradition continues!

This is a conservative estimate of the research activity around Marmorkrebs, because it only includes journal articles, not doctoral theses or the Forum Flusskrebse articles and the like.

As with previous years, the articles are roughly evenly split between interest in Marmorkrebs as a lab animal used for basic research, and Marmorkrebs as an potential or actual invasive species. And indeed, reports emerged (not yet published) of Marmorkrebs in three more countries: France, Denmark, and Israel. The latter is the first report from the Middle East.

Like their introductions into natural ecosystems, the research trendline shows no signs of slowing down.

Update, 14 January 2020: Another paper came out with a 2019 cover date, so the graph is now updated!

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04 January 2020

Lyko, 2020

Lyko F. 2020. Epigenetic adaptation in a clonal invasive crayfish. Symposium presentation at Society for Integrative and Comparative Biology, 3-7 January 2020, Austin, Texas, USA. http://vps40083.inmotionhosting.com/~sicb/meetings/2020/schedule/abstractdetails.php?id=3


The parthenogenetic marbled crayfish (Procambarus virginalis) is a novel species that has rapidly invaded and colonized various different habitats. Remarkably, adaptation to different environments appears to be independent of the selection of genetic variants, as marbled crayfish represent an evolutionary young and genetically homogeneous clone. It therefore seems likely that marbled crayfish adaptation depends on epigenetic mechanisms. We have recently established the complete genome sequence of the marbled crayfish and identified an active DNA methylation system, thus establishing the capacity for epigentic regulation of this genome. We are now using integrated analysis of DNA methylation, chromatin and gene expression datasets to characterize the regulatory mechanism(s) used for epigenetic adaptation in marbled crayfish. In addition, we are analyzing epigenetic modification patterns of animals from ecologically distinct habitats at the population scale. Our results provide novel insights into invertebrate DNA methylation and its function in adaptive gene regulation.

Keywords: None provided.

(Note: This presentation was scheduled to be part of the symposium, “Building Bridges from Genome to Phenome: Molecules, Methods and Models.” It was not presented due to author’s inability to travel.)