Ecological and morphological correlations in the setation patterns of Gammarus Fabricius, 1775 (Amphipoda) from the southern Zagros Mountains, Iran

The southern limits of the Zagros Mountains (Iran) include various aquatic habitats ranging from cold purely fresh to warm saline springs, many of them in isolated watershed basins. Diverse habitats could be correlated with morphological variation in freshwater taxa, as in for example, highly variable patterns of setation in amphipods. We measured length and density of the setae on selected appendages in six species of Gammarus Fabricius, 1775 collected from 14 locations (two species being sympatric) and tested for correlation with seasonal mean water temperature, dissolved oxygen, salinity, and pH of their respective habitats. The results were analyzed using analysis of variance, linear model, and correlation analysis. These regions showed significant variation in the selected ecological factors, and the species had significantly different patterns of setation. It may be supposed that increasing setation in gammarids can improve ventilating activity and hence their respiratory efficiency at higher temperatures and salinity conditions. This correlation may reflect selective pressure on the speciation of gammaridean amphipods in the southern Zagros region.