Taxonomy and bionomics of Tanytarsus recurvatus Brundin, 1947

Tanytarsus recurvatus Brundin was found to develop in the shallow littoral zone (depths 0.4-1.2 m) of two small oligotrophic lakes situated in northern Russian Karelia, near the Polar Circle. Immature stages and the adult male were associated by comparing partial COI gene sequences (so-called DNA barcodes) and individual pharate males. The pupa and larva of T. recurvatus are described in detail, diagnosed and illustrated; morphology of the adult male and DNA barcodes are compared with the presumably most closely related species T. allicis Sublette and T. buckleyi Sublette. The presence of accessory teeth on the larval mandible will place T. recurvatus in the “lugens-type” group used in palaeolimnological studies although the species taxonomically is not related to the lugens-group. Larvae were found to be common in three littoral habitats, which strongly differ from each other in bottom conditions. In one of the studied habitats, T. recurvatus was among the most abundant chironomid species and the only Tanytarsini species found. This habitat is composed of silted sand covered with a 1-5 cm layer of detritus with soft macroscopic colonies of Scytonema mirabile. Emergence of adults was observed from early July to late August or mid-September and presumably occurred, as the water temperature was higher than 10-11°C. Analysis of gut contents showed that larvae of later instars mostly feed on detritus; diatoms, green algae (both unicellular and filamentous) and some filamentous Cyanobacteria (Phormidium) may be abundant in their guts as well; cells or colonies of other Cyanobacteria were almost absent. According to our laboratory and field observations, larvae of T. recurvatus are active tube builders. They use particles of different origin and probably play a substantial role in structuring and transformation of bottom littoral substrates.