Complete mitochondrial genomes of Triodontophorus serratus and Triodontophorus nipponicus, and their comparison with Triodontophorus brevicauda.

The study presents the complete mitochondrial genome sequencing of Triodontophorus serratus and Triodontophorus nipponicus, two common nematodes found in the horse digestive systems. The findings provide valuable genetic markers for further understanding the molecular ecology, systematics, and population genetics of these species.

Mitochondrial Genome Sequencing

• The research focused on mapping the full mitochondrial genome of T. serratus and T. nipponicus, two nematodes commonly found in the large intestines of horses.
• These genomes are circular molecules, with respective lengths of 13,794 base pairs (bp) and 13,701 bp.
• In total, 36 genes were found in these genomes, broken down into 12 protein-coding genes, two rRNA (ribosomal RNA) genes, and 22 tRNA (transfer RNA) genes.
• All identified genes were found to be transcribed in the same direction, matching the traditional GA3-type gene arrangement.

Comparisons and Phylogenetic Relationships

• When comparing these genomes to that of Triodontophorus brevicauda, it was found that T. serratus and T. nipponicus both had two non-coding regions, as opposed to the three found in T. brevicauda.
• To further understand the genetic relationships between these species and others, phylogenetic trees were reconstructed using the amino acid sequences of the 12 identified protein-coding genes.
• These analyses showed that the three Triodontophorus species clustered together, indicating a close genetic relationship with solid statistical support.
• The genera of Strongylus and Triodontophorus, while both belonging to the Strongylinae subfamily, did not cluster together. Interestingly, Triodontophorus showed a closer genetic relationship to Cylicocyclus insigne, Cylicocyclus nassatus, and Cylicostephanus goldi in the Cyathostominae subfamily than to Strongylus.

Implications and Applications

• The results of this study provide valuable genetic markers for future research on these nematode species, facilitating further exploration of their molecular ecology, systematics, and population genetics.
• This sequencing information can improve our biological understanding of these nematodes, potentially leading to more effective strategies for their control in equine health.