FEEDING STRATEGY OF EARTHWORMS IN MOUNTAI N PERMAFROST SOILS

The effect of temperature of the feeding activity of earthworms inhabi ting the mountain permafrost soils was studied in the Upper Kolyma reg ion (Magadan district). Experimental studies were carried out on a pol yploid form Eisenia nordenskioldi (Eisen) (Lumbricidae, Oligochaeta), the only lumbricid species occurring in natural habitats of this regio n. Earthworms were acclimated in the laboratory to various temperature s from 1 to 25-degrees before estimating the feeding activity. The pop ulation of E. nordenskioldi under study showed the normal feeding patt erns in the temperatures range 10-25-degrees with the maximum food con sumption at 15-20-degrees. The daily food consumption in the optimum t emperature zone averaged 800-1000 mg/g body mass, while the time of fo od passage through the digestive tract amounted to 6-7 h. As compared with the other geographical populations, the Kolyma population is char acterized by a wide temperature range of feeding activity and by a shi ft of their optimum zone to the upper threshold of the normal life act ivity for the earthworms. Specific features of feeding of the Kolyma p opulation are discussed with special reference to the hydrothermal con ditions of the earthworm microhabitats. The feeding strategies of the E. nordenskioldi population from the Upper Kolyma mountain soils, Arct ic tundra of the Taimyr peninsula and forest soil of the temperature z one are compared.