Monitoring and assessing aquatic ecosystems using the behavior of organisms is essential for sustainable ecosystem management. Oligochaetes, which inhabit various freshwater ecosystems, are frequently used to evaluate the environmental conditions of freshwater ecosystems. Tubifex tubifex (Müller, 1774) (Oligochaeta, Tubificidae) is tolerant to organic pollution and has been used to evaluate the toxicity of toxicants, including heavy metals. We studied the behavioral responses of T. tubifex to three different copper concentrations (0.1, 0.5, and 1.0 mg L-1). The specimens were exposed to copper in an observation cage containing 150 mL of dechlorinated water. Movement behavior (diameter, speed, acceleration, meander, and turning rate) was continuously observed for two hours before and after the copper treatments. After the treatments, the diameter shrank and showed rapid twisting movement under all the copper conditions. The turning rate had a positive correlation with meander and acceleration both before and after treatment at all three concentrations, whereas speed and meander had a negative correlation. Length and turning rate also showed a negative correlation. The correlation coefficient between speed and acceleration in the highest copper concentration changed from positive before treatment (r=0.64) to negative (r= - 0.52) after treatment. Our results present the possibility of using behavioral parameters to detect copper contamination in freshwater ecosystems.

The oligochaete worms in the genus Nais are common to freshwater habitats. These worms have a highly-developed prostomium and pigmented eye spots. All species have hair chaetae, bifid or single pointed needle chaetae on the dorsal side and ventral chaetae beginning in II with bifid crotchets. Most species of Nais genus live in areas where bottom is covered by sand, gravel or organic matter in aquatic plants. Currently, 26 species of Nais have been recorded worldwide. From the recent faunal studies, 3 species of Nais have been newly reported in Korea. Here, we newly report 6 species of Nais with diagnosis, illustrations and identification keys to Korean Nais species: N. behningi, N. pseudobtusa, N. simplex, N. bretscheri, N. stolci and N. elinguis.

Two newly recorded opheliid polychaetes, Armandia amakusaensis Saito, Tamaki and Imajima, 2000 and Polyophthalmus qingdaoensis Purschke, Ding and Müller, 1995, from Korean waters are reported with the descriptions and illustrations. Armandia amakusaensis can be clearly distinguished from its congeners by the following characteristics: the prostomium has 2 or 3 subdermal eyespots; total number of setigers are 29; the branchiae are present on the setigers from the setiger 2 to the second or third from the last setiger; the lateral eyespots beginning from the setiger 7 are composed of 11 pairs; the anal funnel has 8~11 papillae and a long cirrus. Polyophthalmus qingdaoensis has the distinguishable characteristics from its relatives as follows: the prostomium has a brain bearing dark pigment-spots; the lateral eyespots are distinct; the body has only dark pigment-streaks on dorsal side. We also provide the keys for distinguishing the species of the genera Armandia and Polyophthalmus from Korean waters.

Aquatic oligochaetes were investigated from a small amount of sediment sampled from the Jung-nang Stream, an urban stream in Seoul, Korea, in November 2012. Sorted oligochaetes were observed under alight microscope in a drop of carbonated water, and then preserved in 70% ethanol. Some specimens were slidemounted using glycerin and Eupharal. As a result, the following 12 species were identified including 8 newKorean records, Bothrioneurum vejdoskyanumStolc, Branchiodrilus hortensis(Stephenson), ChaetogastercristalinusVejdosky, Nais communisPiguet, Nais pardalisPiguet, Dero obtusad’Udekem, PiguetielladenticulataLiang, and Haemonais waldvogeli Brescher and 4 additional known species, Limnodrilus hoffmeisteriCleparéde, Branchiura sowerbyi Beddard, Chaetogaster diastrophus(Gruithuisen), and Stylaria fossularisLeidy.This study shows how freshwater oligochaetes are diverse even in urban streams in Korea, if a propersamplingand examining method is employed.