Berman D.I., Leirikh A.N, Bessolitzina E.P. 2017. [Biotopical distribution and resistance to cold of click beetles (Coleoptera, Elateridae) in the Upper Kolyma basin] // Euroasian Entomological Journal. Vol.16. No.2: 129–140 [in Russian, with English summary].
Institute of Biological Problems of the North, Far East Branch, Russian Academy of Sciences, Portovaya Str. 18, Magadan 685000 Russia.
Sochava Institute of Geography, Siberian Branch, Russian Academy of Sciences, Ulan-Batorskaya Str. 1, Irkutsk 664033 Russia.
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ABSTRACT. Biotopical distribution and resistance to cold of click beetles (Coleoptera, Elateridae) were studied in the basin of the Upper Kolyma, a region with extremely cold and long winter. Of the 45 species inhabiting the region, 16 are common, but only three occur in different habitats. Super-cooling points were measured at wintering insects (larvae of 9 species, imagoes and larvae of 4 species), as well as thresholds of long-term tolerated temperature, content of water, reserved and cryoprotective substances (lipids, polyols, sugar). All three known strategies of resistance to cold for invertebrates were revealed in the family Elateridae. Super-cooling prevails (in larvae of 8 and imagoes of 3 species), beetles Hypnoidus hyperboreus and larvae Denticollis varians winter in frozen state. Protective dehydration is peculiar to larvae of Hypnoidus hyperboreus, Oedostethus kolymensis, Oe. nubilus and Oe. mediocris; water content in their bodies decreases from 70% in the summer to 30% in the winter. An increase in resistance to cold by representatives of all three groups can be accompanied by an accumulation of low molecular cryoprotective substances (polyols up to 4.8%, sugar up to 0.45%); however, these were not found in larvae of Denticollis varians wintering in a frozen state. Most of the species of click beetle larvae examined in detail, despite different strategies of resistance to cold, can tolerate 25 °C for a long time, which is sufficient for wintering at a depth of 7–10 cm over the most part of low-mountain relief of the region during moderately harsh winters. Only larvae of D. varians survive temperatures below 40 °C in a frozen state. Comparison of those data and minimal temperature in winter habitats leads one to suppose that biotopical distribution of click beetle larvae is not determined by winter factors.
KEY WORDS: click beetles, cold hardiness, adaptive strategy, overwintering, cryoprotectants, upper Kolyma river basin.