Circumpolar occurrence of eugregarinid protozoanCephaloidophora pacificaassociated with Antarctic krill,Euphausia superba

Abstract

AbstractThe geographical distribution of protozoan parasiteCephaloidophora pacificaAvdeev (Order Eugregarininda) associated with Antarctic krill,Euphausia 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 pacificawas found at all stations around the Antarctic, with 96.4% of the euphausiids infected (n = 195). The numbers ofC. pacificaper krill ranged from 0 to 8089 krill-1, and the average was 350.0 ± 787.8 (mean ± SD). The frequency distributions ofC. pacificashowed 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 ofC. pacificathe maturity stage of krill did, with an increasing intensity of infection as krill matures. The infestation ofE. superbaby eugregarinid protozoan is considered to be a circum-Antarctic phenomenon, and it occurs equally throughout the Southern Ocean.