29 January 2021

Ranja Andriantsoa interview

Ranja Andriantsoa

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


Invasion of the crayfish clones: Q&A with Ranja Andriantsoa

22 January 2021

Maiakovska and colleagues, 2021

Communications Biology logo.
Maiakovska O, Andriantsoa R, Tönges S, Legrand C, Gutekunst J, Hanna K, Pârvulescu L, Novitsky R, Weiperth A, Sciberras A, Deidun A, Ercoli F, Kouba A, Lyko F. 2021. Genome analysis of the monoclonal marbled crayfish reveals genetic separation over a short evolutionary timescale. Communications Biology 4(1): 74. https://doi.org/10.1038/s42003-020-01588-8



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. 

Open access

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.

19 January 2021

Harper’s magazine features Marmorkrebs in Madagscar

Harper's February 2021 cover
Rowan Moore Gerety has just published the best article ever written about Marmorkrebs.


“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:

Illustration of marbled crayfish overlaying a map of Madagascar

I’ll forgive that the abdomen probably can’t bend quite that much.


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/

04 January 2021

Stein and colleagues, 2020

The Journal of Undergraduate Neuroscience Education logo
Stein W, Talasu S, Vidal-Gadea A, DeMaegd ML. 2020. Physiologists turned Geneticists: Identifying transcripts and genes for neuronal function in the marbled crayfish, Procambarus virginalis. The Journal of Undergraduate Neuroscience Education 19(1): A36-A51. https://www.funjournal.org/wp-content/uploads/2020/11/june-19-36.pdf




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


Open access