A new earthworm species of the genus Eisenia Malm, 1877 (Oligochaeta, Lumbricidae) from the Ili River valley, northwestern China

The present study focuses on the taxonomy of the earthworm genus Eisenia Ealm, 1877 in China. The taxonomic framework for this genus in China has long been ambiguous, with studies in the northwestern region being particularly scarce. Prior to this research, only four subspecies within the Eisenia nordenskioldi (Eisen, 1879) complex, distributed across northeastern and northern China, had been described.

Based on detailed morphological characteristics and molecular data, this paper describes a new species, E. ilensis sp. nov., collected from the Ili River valley in northwestern China. The key diagnostic characteristics of this new species include a medium body length (37–103 mm); two pairs of small, spherical spermathecae without ducts, located at the inter-segmental furrows 9 / 10 and 10 / 11; a pair of small, circular tubercula pubertatis on the clitellum situated between the ab setae; the first of dorsal pore beginning at the 4 / 5 inter-segmental furrow; and a pair of slit-like male pores on segment XV.

Phylogenetic analyses based on the mitogenomic protein coding genes indicate that E. ilensis sp. nov. forms a distinct clade with E. balatonica Pop, 1943 supporting its status as an independent species and a basal evolutionary status. The discovery of the new species of E. ilensis sp. nov. not only enriches the species diversity of the genus Eisenia in China but also provides a crucial taxonomic foundation for subsequent research into the evolution and dispersal history of this genus in Eurasia.