Rowan Moore Gerety, author of the excellent Harper’s article on Marmorkrebs in Madagascar, continues his coverage of the story with another outstanding piece. This is an interview with Ranja Andriantsoa.
The article also has a nice video which is one of the best I’ve seen for giving a sense for just how abundant Marmorkrebs are in Madagascar.
External links
Abstract
The marbled crayfish (Procambarus virginalis) represents a very recently evolved parthenogenetic freshwater crayfish species that has invaded diverse habitats in Europe and in Madagascar. However, population genetic analyses have been hindered by the homogeneous
genetic structure of the population and the lack of suitable tools for data analysis. We have used whole-genome sequencing to characterize reference specimens from various known wild populations. In parallel, we established a whole-genome sequencing data analysis pipeline for the population genetic analysis of nearly monoclonal genomes. Our results provide evidence for systematic genetic differences between geographically separated populations and illustrate the emerging differentiation of the marbled crayfish genome. We also used mark-recapture population size estimation in combination with genetic data to model the growth pattern of marbled crayfish populations. Our findings uncover evolutionary dynamics in the marbled crayfish genome over a very short evolutionary timescale and identify the rapid growth of marbled crayfish populations as an important factor for ecological
monitoring.
Keywords: None provided.
Additional: Blog post by two of the authors about this paper:
Tönges S, Lyko F. 2021. Population growth and utilization of clonal marbled crayfish. Nature Ecology and Evolution. https://natureecoevocommunity.nature.com/posts/population-growth-and-utilization-of-clonal-marbled-crayfish-18289693-c2e2-4213-b624-26c114b5b428 2021.
“Stowaways” appears in the February 2021 issue of Harper’s magazine. It’s a feature-length examination of the invasion of Marmorkrebs on Madagascar. It was prompted by conversation with Julia Jones and was almost two years in the making.
There is some science, but the bulk of the article is a nuanced, detailed examination of the complexities of living with environmental change.
Over and over again, people are ambivalent to Marmorkrebs. People recognize the crayfish is a pest... but it’s a cheap meal. In a place where most people are living on the equivalant of a couple of US dollars a day, that matters.
In the hills above town, where rice cultivation depends on rainfall for irrigation, farmers complain that the levees of their terraced paddies spring leaks without warning, sparking arguments when valuable rainwater drains into their neighbors’ fields instead. Most realize that crayfish burrows are to blame, but suspicions linger all the same. “The tsi pe’peo is an enemy of agriculture,” Ramandrosoa told me. Nevertheless, he hesitated to advocate for its eradication. For families without even enough money to pay their children’s school fees, he said, “It’s kerosene, it’s sugar, it’s soap. It’s the basic necessities.” In the lean months, Ramandrosoa explained, “People collect crayfish so they don’t have to sell their rice.”
I also love the illustrations by Barry Falls. Look at this gem:
I will probably be rereading this many times. It’s a rich and insightful part of a story that I know from the published literature, but this shows just how little of the story makes it into journal articles.
Highly recommended.
External links
Gerety RM. 2021. Stowaways. Harper’s 342(2049): 72-79. https://harpers.org/archive/2021/02/stowaways-crayfish-madagascar/
Abstract
The number of undergraduate researchers interested in pursuing neurophysiological research exceeds the research laboratory positions and hands-on course experiences available because these types of experiments often require extensive experience or expensive equipment. In contrast, genetic and molecular tools can more easily incorporate undergraduates with less time or training. With the explosion of newly sequenced genomes and transcriptomes, there is a large pool of untapped molecular and genetic information which would greatly inform neurophysiological processes. Classically trained neurophysiologists often struggle to make use of newly available genetic information for themselves and their trainees, despite the clear advantage of combining genetic and physiological techniques. This is particularly prevalent among researchers working with organisms that historically had no or only few genetic tools available. Combining these two fields will expose undergraduates to a greater variety of research approaches, concepts, and hands-on experiences. The goal of this manuscript is to provide an easily understandable and reproducible workflow that can be applied in both lab and classroom settings to identify genes involved in neuronal function. We outline clear learning objectives that can be acquired by following our workflow and assessed by peer-evaluation. Using our workflow, we identify and validate the sequence of two new Gamma Aminobutyric Acid A (GABAA) receptor subunit homologs in the recently published genome and transcriptome of the marbled crayfish, Procambarus virginalis. Altogether, this allows undergraduate students to apply their knowledge of the processes of gene expression to functional neuronal outcomes. It also provides them with opportunities to contribute significantly to physiological research, thereby exposing them to interdisciplinary approaches.
Keywords: undergraduate • peer-mentoring • GABA • Marmorkrebs • neurophysiology • gene annotation • decapod • crustacean
As if there weren’t enough reasons to hate 2020, the number of Marmorkrebs papers published was down from the last two years.
It’s impossible to tell if the dip in number of publications is the result of a global pandemic or just the regular up and down you see in these sorts of data.
Marmorkrebs did make international news again this year, mainly because a cloning crayfish invading a cemetery is a great story for Halloween. That was the first record of Marmorkrebs in Belgium, but another first record – on the island of Taiwan – made for fewer news stories but may have been more important in showing how Marmorkrebs are spreading globally.
On the legislative front, Marmorkrebs (and other crayfish) were banned in Japan, the American state of Michigan, and the Canadian province of Saskatchewan. Several jurisdictions like North Carolina and Ontario are considering following suit.
Update, 4 January 2021: Have just found another paper with a 2020 release (Stein and colleagues, 2020), so the count shown in the graph is one too low.
Related posts
2008 was the best year ever for Marmorkrebs research
2009 was tied for the best year ever in Marmorkrebs research
2010 was the best year ever for Marmorkrebs research
2011 was not the best year ever for Marmorkrebs research
2012 was an average year for Marmorkrebs research
2013 was the second best year ever for Marmorkrebs research
2014 was a good year for Marmorkrebs research
2015 was the best year ever for Marmorkrebs research
2016 was the best year ever for Marmorkrebs research
2017 was the second best year ever for Marmorkrebs research
Abstract
Knowledge of the morphological features of crayfishes native to New Guinea is limited in many cases, the internal morphology, gastric mills, and mandibles of six species of Cherax species (Decapoda: Astacidea: Parastacidae) from this island were described and illustrated. The measurements were compared with those of parastacid crayfish from Madagascar and New Zealand, with Enoplometopoidea from coral reefs, and Nephropidea from deep sea. Characters peculiar to the family Parastacidae were found both in gastric mills and mandibles, and differences between the morphology of mandibles in freshwater and marine species from the infraorder Astacidea were found. Relationships between functional morphology and feeding behaviour were discussed.
Keywords: None provided.
Abstract
In recent years, there has been increasing concern about the ecotoxicological consequences of the drug Diclofenac on freshwater organisms. Influences on the largest freshwater invertebrates, the freshwater crayfish, are especially interesting in the context of cascading effects due to their important role as keystone species. In this study, lethality, influences on body weight, embryonic development and histological changes in embryos of marbled crayfish (Procambarus virginalis) as well as noble crayfish (Astacus astacus) were investigated in response to their exposure to different concentrations of Diclofenac. Additionally, the suitability of marbled crayfish as a model organism for endemic freshwater crayfish was established when studying the effects of Diclofenac. For both species, lethal effects started at concentrations of 10.24 mg/L Diclofenac, weight was not affected, embryonic development slowed down from concentrations of 0.16 mg/L and histological changes were visible from concentrations of 0.64 mg/L. The similarity of LOEC (Lowest Observed Effect Concentrations) between the two species showed that marbled crayfish can serve as a model for native crayfish when investigating the effects of exposure to Diclofenac.
Keywords: marbled crayfish • noble crayfish • juveniles • Diclofenac • embryonic
