RESEARCH NEWS STORY
August 2, 2023
Chiba University

How the Tropical Red Swamp Crayfish
Successfully Invaded the Cold Regions of Japan
Researchers from Japan have identified the molecular mechanisms that allow the red swamp
crayfish to develop cold tolerance and, thus, colonize cold regions
The red swamp crayfish—found originally in tropical regions—has become a highly invasive
species across the globe. Over the years, they have successfully colonized habitats muchcolder than their original habitats, but the factors determining their cold resistance haveremained elusive. Recently, a group of researchers in Japan has discovered genes that may
help the red swamp crayfish produce protective proteins and adapt to the cold.

Red swamp crayfish(Procambarus clarkii)
U.S.

SapporoNew Orleans
Imported into
Japan in 1927

Kamakura
Spread throughout Japan

Image title: The route of invasion of the red swamp crayfish in Japan
Image caption: The red swamp crayfish—originally imported from New Orleans, USA, to Kamakura,
Japan, in 1927—spread throughout the Japanese archipelago except for Hokkaido, the northernmost
island of Japan, over the years and became one of the most notorious non-native freshwater
invertebrates by the 1950s. A recent study, however, reported the possibility that some populations
settled in Sapporo City of central Hokkaido, where water temperatures become extremely low during
the winter.
Image credits: Daiki Sato and Takashi Makino

License type: Original content

Owing to human activities and climate change, many animal species have invaded newhabitats. Such biological invasion comes with devastating impacts on the local biodiversity
and ecosystems. The red swamp crayfish—known to the scientific world as Procambarus
clarkii (P. clarkii)— is no exception. P. clarkii is a freshwater crayfish native to the tropicalregions of southern USA and northeastern Mexico. After their introduction to different partsof the world, they have become one of the most widespread and invasive animal species.
They are known for their adaptability and aggressive behavior that ensure their survival in awide range of environments, even in regions much colder than their original habitats.
Given that P. clarkii is typically limited to subtropical climates, researchers have longendeavored to find a few P. clarkii populations in the colder regions of Japan. In Hokkaido,
the northernmost island of Japan, P. clarkii populations have been observed in a limited
number of rivers and ponds where water from hot springs or sewage treatment plants flows
in and contributes to high water temperatures throughout the year. A recent report, however,describes some populations settled in Sapporo City of central Hokkaido, where watertemperatures become extremely low during the winter. A group of researchers from Japan,
including Dr. Daiki Sato, Assistant Professor in the Graduate School of Science of Chiba
University, and Professor Takashi Makino from Tohoku University sought to study the genetic
changes that have allowed the crayfish to adapt to these cold environments. Their study was
made available online on July 3, 2023, and will be published in Volume 26, Issue 8 of thejournal iScience on August 18, 2023. Their article was additionally selected and included in
the journal’s special issue, “Invasion Dynamics.”
Speaking about the motivations behind their study, Prof. Makino, who led the study, says,“Although the red swamp crayfish has been a well-known and notorious invasive species inJapan for quite some time, nobody has examined its genomic and transcriptomiccharacteristics that contribute to its invasiveness yet, thus motivating us to pursue this study.
We feel our study has far-reaching ecological implications.”
Accordingly, the researchers studied P. clarkii from different populations in the newly
colonized Japan and the originally inhabited USA. They compared differences in cold
tolerance and related genetic characteristics among the samples. They also studied theeffects of natural selection by comparing changes in gene sequences among the samples.
When asked about the main findings of the study, Dr. Sato, the first and co-corresponding
author of the study, exclaims, “A population of red swamp crayfish in Sapporo, Japan may
have acquired genetic changes that enhanced its cold tolerance. We have revealed the genes
and genomic architecture possibly involved in the cold adaptation mechanism.”
The researchers found that different P. clarkii populations, even within Japan, responded
differently to the cold: some showed no significant changes in gene expression over time,
while others displayed noticeable differences between the beginning and the end of theexperiment.
Notably, they discovered regulatory changes in a group of genes involved in developing theprotective outer layer of P. clarkii, called the cuticle. They also found an increase in theproduction of peptidase inhibitors—proteins that prevent the enzymatic degradation ofproteins in the body. These peptidase inhibitors play a role in preserving protective proteinsfrom being cold-damaged, thus contributing to cold resistance in P. clarkii.
Further, the researchers also found that some of the studied genes had undergone significant
levels of duplication that resulted in a large number of copies of the same genes within thegenome. This duplication may have amplified the genes’ functional abilities in dealing with
low temperatures.
These results provide valuable insights into the molecular mechanisms adopted by invasive
species to develop cold resistance and survive in cold habitats. When used in the right context,
these findings could have potential medical applications.
Overall, these findings significantly contribute to our understanding of invasive species, which
may help us take measures to prevent their spread and, in turn, protect global biodiversity.
About Assistant Professor Daiki SatoDr. Daiki Sato is an assistant professor at the Institute for Advanced Academic
Research/Graduate School of Science, Chiba University. He works to unravel the molecularmechanisms and ecological functions underlying behavioral diversity in animals. His researchinterests include evolutionary genomics and behavioral ecology. He is a member of theSociety for Evolutionary Studies, Japan, and The Ecological Society of Japan.
Reference
Title of original paper: Genomic adaptive potential to cold environments in the invasive red swamp
crayfishAuthors: Daiki X. Sato 1, 2, 3, Yuki Matsuda3, Nisikawa Usio4, Ryo Funayama5, Keiko Nakayama5, andTakashi Makino3
Affiliations:
1
Institute for Advanced Academic Research, Chiba University
2
Graduate School of Science, Chiba University
3
Graduate School of Life Sciences, Tohoku University
4
Institute of Nature and Environmental Technology, Kanazawa University
5
Department of Cell Proliferation, United Center for Advanced Research and Translational Medicine,
Graduate School of Medicine, Tohoku University
Journal: iScience
DOI: 10.1016/j.isci.2023.107267
Contact: Daiki X. Sato, Institute for Advanced Academic Research, Chiba University, Japan
Email: daikisato@chiba-u.jp
 Takashi Makino, Graduate School of Life Sciences, Tohoku University, Japan
Email: tamakino@tohoku.ac.jp
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