“A recent research published in the Scientific Reports reinvestigated the taxonomy of the giant salamander A. japonicus using the latest mitochondrial DNA typing and carbon dating.”
Key Topics:
Summary:
- The length of the world’s largest salamander is ~ 1.8 m and belongs to the genera Adrias and Cryptobranchus.
- The giant salamander fossils are approximately 3,500 to 4,100 years old.
- Mitochondrial DNA typing is the gold standard technique for investigating sequence-level taxonomy.
Research insights:
The present research, published by Noda et al., entitled “Ancient DNA Integrates Fossil and Modern Giant Salamander Taxonomy,” focused on establishing the taxonomic relationship of the giant salamander fossils obtained from a cave on Shikoku Island, Japan.
Two extensive techniques, mitochondrial DNA typing and carbon dating, have been selected to evaluate the nucleic acid sequence information and the fossil age, respectively.
The mtDNA typing technique has been instrumental in studying ancient DNA samples. The reason being, its availability and intactness. In addition, it can also establish a clear lineage between maternal species as mitochondria (and so the mtDNA) are inherited maternally.
In addition to this, they considered the morphological characters of bones during the study, followed by phylogenetic analysis.
The mitochondrial DNA typing revealed the similarities between fossils and the Japanese giant salamander, A. japonicus. However, no complete mitochondrial DNA sequence was obtained.
The phylogenetic analysis showed that the fossils belong to the Western Japan clade of the species A. japonicus. The carbon dating data revealed the age of the fossil between 3,500 to 4,100 years.
What is mitochondrial DNA typing?
mtDNA is significantly different from the nuclear DNA and has a pivotal role in ancient DNA studies. This circular DNA remains stable and intact for thousands of years as it is protected by the mitochondrial membrane.
Alongside, the high copy number and direct maternal inheritance also offer unique benefits during DNA typing. High-purity DNA has been isolated from the fossil samples and sequenced to decode the nucleotide sequence.
The obtained sequence, then used to prepare the phylogenetic tree and to establish the relationship between species. Our previous articles will help you learn more about mitochondrial DNA typing and its importance.
You can explore articles provided in various links.
Key Takeaways:
- Ancient DNA typing is significantly important for species identification. Techniques like mitochondrial DNA typing allow investigating an organism or fossil DNA even in the absence of nuclear DNA.
- It provides the most accurate and sequence-specific information and also helps establish accurate phylogenetic relationships between species.
- While mtDNA typing is commonly used in studies of ancient humans and other animals, this study is unique in applying the technique to amphibian research.
- One key takeaway from the present study is that ancient DNA typing becomes more valuable when combined with other techniques like carbon dating.
Research information:
| Original article name | Ancient DNA Integrates Fossil and Modern Giant Salamander Taxonomy |
| Published Date | 09 June 2025 |
| Journal name | Scientific Reports |
| Authors | Masahiro Noda, Takushi Kishida, Hiroyuki Kitagawa, Ibuki Fukuyama & Kanto Nishikawa |
| Institution | Graduate School of Human and Environmental Studies, Kyoto University, Yoshida Nihonmatsu, Sakyo, 606-8501, Kyoto, Japan |
| Techniques | Mitochondrial DNA typing, carbon dating and phylogenetic study |
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Source:
Noda, M., Kishida, T., Kitagawa, H. et al. Ancient DNA integrates fossil and modern giant salamander taxonomy. Sci Rep 15, 18642 (2025). https://doi.org/10.1038/s41598-025-03496-5.
