Circumpolar occurrence of eugregarinid protozoan Cephaloidophora pacifica associated with Antarctic krill, Euphausia superba

The geographical distribution of protozoan parasite Cephaloidophora pacifica Avdeev (Order Eugregarininda) associated with Antarctic krill, Euphatisia superba, was examined in samples collected from the vicinity of the Antarctic Peninsula, near Syowa Station, and Pacific and Indian sectors of the Southern Ocean. Cephaloidophora pacifica was found at all stations around the Antarctic, with 96.4% of the euphausiids infected (n = 195). The numbers of C pacifica per krill ranged from 0 to 8089 krill(-1), and the average was 350.0 +/- 787.8 (mean +/- SD). The frequency distributions of C. pacifica showed an overdispersed parasite population (i.e. the variance was greater than the mean) at all locations. Statistical analysis showed that whilst the geographical location did not have a significant effect on intensity of C. pacifica the maturity stage of krill did, with an increasing intensity of infection as Krill matures. The infestation of E. superba by eugregarinid protozoan is considered to be a circum-Antarctic phenomenon, and it occurs equally throughout the Southern Ocean.