Biodiversity of aquatic macrobenthoses and the first record of the Horsetail worms (Nematomorpha: Gordiidae) in Marbor River - Isfahan Province

In an investigation of the effects of the effluent of fish farms on the water quality of the Marbor River in Isfahan province based on biological indicators, some cases of infection of macrobenthos with horsehair worms (Nematomorpha: Gordiidae) were observed. About 76% of the observed worms were observed to leave their hosts. the horsehair worms were identified in only three families of aquatic insects, including Hydropsychidae, Limoniidae, and Chironomidae. About 24% of the observations were free living worms in the sediments. The highest and the lowest frequencies of observations were recorded in spring (47.7%) and autumn (0.92%), respectively. The seasonal abundance of free-living mature and fertile worms was a coincidence with increasing the reproductive activities of aquatic insects. Aaccordingly, it can be concluded that the ecological rules enforced such a simultaneous phenomenon to ensure that the worm larvae can find a proper host.