[Quantitative analysis of the invasion with gregarinids (Sporozoa: Gregarina) of the euphausiid Thysanoessa raschii (Crustacea: Euphausiacea) from the Barentsev sea].

An occurrence of the gregarinids in the gastrointestinal tract of euphausiid Thysanoessa raschii was studied in summer 1982 and winter 1983 in the southern part of the Barents Sea. The infection rates of T. raschii with gregarinids was 0% in winter and 89.4% in summer. The highest level of infection was 1035 gregarinida per crustacean. The level of infection was found to be related mainly to be food composition (no gregarinids was found in euphausiids with copepods in stomach, the high level--in crustaceans with phytoplankton in the gastrointestinal tract).