Investigation of Sexual Dimorphism in Niphargus persicus (Crustacea: Amphipoda)

Introduction: Members of the genus Niphargus are crustaceans that live in fresh underground waters in the western Palearctic of Iran. These environments are characterized by the absence of light, stable climate, constant temperature, and limited food supply. The degree of morphological variation in different groups of crustaceans varies, and quantitative research on morphological traits has been conducted to investigate sexual dimorphism in some taxa, especially in species of the genus Niphargus. The aim of this research is to investigate sexual dimorphism in N. persicus species.
Materials & Methods: The geographic location of the type specimens of species is in the Tire Bagh spring in Marvdasht City, Fars province. In this study, the source location of this spring was excavated with a pickaxe and shovel, and the specimens were separated from the sand and gravel using a sieve and dark nets and fixed with alcohol. Subsequently, the gender of the specimens was determined. Then, examine the diagnostic characteristics of the species and compare the traits between male and female specimens, the animal body parts were dissected using dissecting needles and separated from each other under a stereomicroscope (SZX9) Olympus, and the prepared slides were studied.
Results: In the first step, samples were sorted based on primary sexual traits, namely the presence of genital papillae between pereopods VII for males and marsupial pouches between pereopods V to VII for females. The results of the analysis and comparison of morphological traits showed that there is sexual dimorphism in this species in traits such as body size, the length of the first antenna, the ratio of distal to proximal articles of the uropod III, the shape and size of the gnathopods I-II, the number of distal and lateral spines on the telson, and the number of lateral projections on the outer lobe spines in Maxilla I.
Discussion: Based on the observed morphological differences between male and female specimens in this study, it can be concluded that there is sexual dimorphism in N. persicus species. These differences, particularly in male specimens, are functional and facilitate the mating process. Additionally, considering the importance and role of morphological traits in the taxonomy of any species, a comprehensive study and examination of these traits can also provide the possibility of identifying different populations of this species based on the gender of the females.