Molecular identification of seven earthworm (Annelida: Oligochaeta) species using DNA barcoding of the 18S rRNA gene region and their relationship with soil properties in Babylon province, Iraq

Document Type : Research Paper

Authors

Department of Biology, College of Science, University of Babylon, Iraq

10.22103/jab.2025.24781.1659

Abstract

Objective
This study aimed to employ molecular techniques to identify and classify earthworm species present in Babylon Province, Iraq, and to examine the extent to which environmental factors influence their distribution and abundance. Given the limited research on Iraqi earthworm fauna, this work sought to provide a clearer understanding of species diversity in the region and to assess how variations in soil characteristics may affect their ecological presence.
Materials and methods
Fieldwork was conducted at three ecologically distinct stations within Babylon Province, each representing unique environmental and land-use conditions. Sampling was carried out across three seasons—fall, winter, and spring-during the 2023–2024 period. Soil samples from each site were analyzed for temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), and moisture content, providing a comprehensive profile of key physicochemical soil parameters. Earthworm specimens were collected manually and preserved for molecular analysis. DNA barcoding using the 18S rRNA gene region was employed to identify the species, and the resulting sequences were submitted to the NCBI GenBank database for comparison and verification.
Results
Seven species were identified through molecular methods: Aporrectodea tuberculata, Aporrectodea caliginosa, Dendrobaena platyura, Fitzingeria platyura, Hormogaster redii, Lumbricus rubellus, and Polytoreutus finni. Statistical correlations revealed that soil moisture and temperature significantly influenced earthworm distribution, with population densities decreasing markedly during warmer periods. These findings suggest that earthworms in this region exhibit strong physiological responses to thermal and hydric stress, which in turn shapes their spatial and seasonal dynamics.
Conclusions
This study confirms the utility of DNA barcoding for accurate earthworm species identification and contributes new data on the biodiversity of Oligochaeta in Iraq. The observed correlations between environmental conditions and earthworm populations highlight the importance of soil management practices in maintaining biodiversity. Future research incorporating wider genomic markers and additional sampling sites is recommended to further elucidate the ecological roles of these organisms across Iraq's diverse habitats.

Keywords

References

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Agricultural Biotechnology Journal
Volume 17, Issue 2
May 2025
Pages 171-196

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