Recent developments in Bonamia research in Virginia and NorthCarolina

摘要

Bonamia spp. are haplosporidian oyster parasites that differ from "classical" haplosporidians like Haplosporidium nelsoni in being directly transmitted between hosts. Like H. nelsoni, however, Bonamia spp. have caused catastrophic oyster mortality and have limited the recovery and restoration of oyster species in the places (Europe, Australia, and New Zealand) these parasites occur. The 2003 appearance of a Bonamia spp. in Crassostrea ariakensis dying in Bogue Sound, North Carolina, raised new questions about the potential success of mid-Atlantic Asian oyster introductions on any scale. Since the discovery of this parasite in fall 2003, we have tracked the monthly prevalence of Bonamia spp. in experimental C. ariakensis populations in Bogue Sound, and generated hypotheses about its source; identified a potential natural reservoir for Bonamia spp.; and began an array of research projects that collectively will characterize risk to C. ariakensis in the mid-Atlantic. From a maximum autumn prevalence of 63%, Bonamia spp. fell below detectable levels in Bogue Sound by March 2004. The parasite reappeared in monthly samples in June (5% to 19% prevalence), but decreased in prevalence again in July and August (0% to 3%), and oyster mortality in 2004 has been low. The reason for, and significance of, reduced Bonamia spp. activity in 2004 is not clear. The long-term persistence of Bonamia spp. in Bogue Sound irrespective of the presence of C. ariakensis is also uncertain, but at least one native species, the crested oyster Ostrea equestris, has been found to harbor this parasite.