Diversity and distribution of Chironomidae (Insecta: Diptera) of the Oued Charef basin,North-Eastern Algeria

Summary. As part of the study of the Chironomidae fauna in lotic waters of North-Eastern Algeria, nine sampling stations in the Oued Charef basin were visited monthly during a study cycle. This work collected 7615 specimens forming a list of 75 species divided into four subfamilies. For North Africa, 23 species are reported for the first time, including six species of Tanypodinae (Paramerina vaillanti, P. berkana, Procladius lugens, Thienemannimyia zousfana, Trissopelopia longimana, Trissopelopia sp. and Zavrelimyia berberi), eight species of Chironominae (Cladotanytarsus vanderwulpi, Cryptochironomus obreptans, C. supplicans, Cryptotendipes usmaensis, Polypedilum sordens, Micropsectra fallax, M. contracta and Tanytarsus sylvaticus), and nine species of Orthocladinae (Cricotopus tibialis, Chaetocladius insolitus, C. piger, Tokunagaia rectangularis, Heterotrissocladius subpilosus, Limnophyes gurgicola, Nanocladius bicolor, Rheotanytarsus distinctissimus and Smittia sp.). In Algeria, 34 species are reported for the first time: seven Tanypodinae, 15 Chironominae and 12 Orthocladinae. In addition to the species reported as new for North Africa, the following ones can be added: Macropelopia nebulosa, Harnischia curtilamellatus, Microtendipes chloris, M. confinis, Polypedilum convictum, Stictochironomus sp., Paratanytarsus dissimilis, Cricotopus fuscus, C. trifascia and Pseudosmittia sp. This study has highlighted factors that control the distribution of the Chironomidae depending on characteristics of each site and the study season. The results have shown that the occurrence and diversity of chironomid species in these streams are significantly influenced by conductivity, temperature, current velocity and the type of substratum, while altitude had no significant effect on chironomid occurrence and distribution. The Motomura analysis and the ecological indices comparison have shown that the sampled stations are widely different. Despite the extreme environmental conditions undergone by streams of this area (eutrophication, high temperatures, drought in summer and water abstraction), Oued Chaniour was the richest and most balanced community, comprising 40 mostly stenotopic species, which require undisturbed conditions.