first record of limnodrilus claparedeianus ratzel, 1868 (annelida: oligochaeta: tubificidae) in anzali wetland, guilan province, iran

oligochaeta worms are important organisms in aquatic ecosystem. their omnipresence makes them as an indicator of environmental changes and health of aquatic ecosystem. the members of the family tubificidae and in particular, genus limnodrilus are considered as the most tolerant oligochaets to aquatic pollution. therefore identification and biological characteristics of this taxon are of great help to evaluate the ecosystem of water bodies. limnodrilus claparedeianus were collected from anzali wetland with a grab of 0.04 m2 capacity at 13 stations from august 2012 through june 2013. penis sheath was one of the main characteristics to identify them. results showed their maximum and the minimum density in spring (601.27±  466.8346 ind.m-2) and in autumn (156.12 ±136.3ind.m-2) respectively which was significantly different (p