Unearthing The Soil’s Hidden Engineers: Three New Earthworm Species Discovered in Mindanao

 By: Jan Pauline Medina Roxas | Resistome

Beneath the rich soils of Misamis Oriental, scientists have unearthed three previously unknown species of pheretimoid earthworms namely, Polypheretime andresi sp. nov., Pheretima elnorroae sp. nov., and Pheretima naawanensis sp. Nov. These discoveries, along with the first record of Metaphire bahli on Mindanao Island, reveals the hidden diversity of the Philippines’ “ecosystem engineers”, tiny organisms that play a crucial role in maintaining healthy soils. Earthworms earn this title for their ability to shape soil structure and fertility through their burrowing and feeding behaviors that enhance microbial activity to sustain countless life forms above and below ground.

Taxonomists defined the novel species’ diagnostic characters through a detailed examination of their internal and external structures such as the gizzard, clitellum, and intestinal caeca. Each species exhibits distinctive morphological traits that set them apart from previously identified taxa. Multiple spermathecal pores and unique genital markings separate Polypheretima andresi from the other species. Pheretima elnorrae features a distinct prostomium type and internal organ arrangement while Pheretima naawanensis had a specific setal pattern and male pore configuration. Taxonomists defined their diagnostic characters through a detailed examination of their internal and external structures such as the gizzard, clitellum, and intestinal caeca.  

These novel species were discovered in the lands of Misamis Oriental such as forested areas, agricultural lands, and moist soils. Their presence in such habitats highlights the ecological richness of Mindanao and its potential as a hotspot for soil biodiversity. Researchers sequenced the complete mitochondrial genomes of the new species to confirm their genetic distinctiveness; protein-coding and ribosomal RNA genes comprised their mitogenomic data that strengthened the morphological findings. Since mitochondrial DNA evolves rapidly, it is a reliable molecular marker for distinguishing closely related species; this makes mitochondrial genome sequencing a powerful tool in modern taxonomy for more accurate species classification.

Phylogenetic analyses were performed using Maximum Likelihood (ML) and Bayesian Inference (BI) methods to determine the evolutionary placement of the new species. These analyses confirmed their distinct lineages within Megascolecidae and clarified relationships among genera such as Pheretima and Polypheretima. This study not only enhances our knowledge of earthworm evolution in the Philippines but also emphasizes the value of integrating molecular data with classical taxonomy. Through identification of new species and expanding known distributions, this research underscores  the need for more research into the nation’s soil ecosystems and Mindanao with its role as a reservoir of undiscovered biodiversity. Ultimately, these findings highlight the critical role of earthworms as ecosystem engineers, vital yet often overlooked contributors to soil health and biodiversity, and stresses the importance of continued exploration of the Philippines’ subterranean life.