The first data on diet peculiarities of the endemic and common caddy-flies, namely three endemic and one introduced, and mollusks, as well endemic and cosmopolitan, were obtained when untypical to Lake Baikal charophyte algae of the genus Spirogyra intensively developed on stone substrates. Diet spectra of these invertebrates were studied. Food compositions of the endemic caddy-flies and gastropodes showed that they grazed periphyton from stones as non-different mass. This is testified by sponge spicules, chitin body fragments of other invertebrates present in digestive tract contents. As earlier a dominant component of their food has been found to be diatom algae despite Spirogyra was abundant and contributed up to 60 % of the periphyton. Not far ago diatoms mostly contributed to the periphyton biomass within first vegetable belts of stone shallows. As we revealed, the invertebrates in the Spirogyra environment were much more passive in grazing than on stones without Spirogyra. 58 % of caddy-fly larvae had empty their digestive tract while other ones contained small amounts of food and gastropode digestive tract were filled in 80-90 % by sand. It was observed that the invertebrates can graze Spirogyra but Spirogyra algae are not familiar food for Baikalian grazers and so they are casual and rare in stomach. The invertebrates have been observed to avoid locations where Spirogyra abounded but Spirogyra influence was found to be not lethal. This question needs a farther special research.

Rozhkova Natalya Anatolyevna, Candidate of Science (Biology), Senior Research Scientist, Limnological Institute SB RAS, 3, Ulan-Batorskaya st., Irkutsk, 664033, Russian Federation, tel.: (3952) 42–82–18, e-mail: rozhkova@lin.irk.ru 

Bondarenko Nina Aleksandrovna, Doctor of Science (Biology), Leading Research Scientist, Limnological Institute SB RAS, 3, Ulan-Batorskaya st., Irkutsk, 664033, Russian Federation, tel.: (3952) 42–82–18, e-mail: nina@lin.irk.ru 

Sitnikova Tatiana Yakovlevna, Doctor of Science (Biology), Leading Research Scientist, Limnological Institute SB RAS, 3, Ulan-Batorskaya st., Irkutsk, 664033, Russian Federation, tel.: (3952) 42–82–18, e-mail: nina@lin.irk.ru

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