The discovery of a new Niphargus species from the southern part of the Alborz Mountains, located at the eastern limit of the genus range

Niphargus species are a significant proportion of freshwater amphipods found in the groundwaters of the Western Palearctic, comprising about a quarter of all known species. Recently, a new species, N. qazvinensis, was discovered in the Samaq Abad Spring located in Qazvin Province, Iran. The identification of this new species was supported by morphological features as well as the analyses of mitochondrial (COI) and nuclear (28S rDNA) gene sequences. Genetic analysis revealed that N. qazvinensis sp. nov. is most closely related to N. urmiensis, N. hakani, and N. fiseri. Notably, N. qazvinensis can be distinguished from other known Niphargus species based on distinct morphological features. These include the presence of two and one robust setae on the postero-dorsal margin of urosomites II and III, respectively. Additionally, the gnathopods I to II propodi are characterized by three and two robust setae with lateral projections on the outer surface in the palmar corner, respectively. Furthermore, maxilla I bears between none to two lateral projections on outer plate robust setae.