||Arzul Isabelle, Bond Celine, Gagnaire Beatrice, Chollet Bruno, Morga Benjamin, Ferrand Sylvie, Robert Maeva, Renault Tristan
||World Aquaculture Society, Aquaculture 2007
||Effects, Temperarature, Salinity, Bonamia ostreae, Parasite, Pathology, Flat oyster, Ostrea edulis, Oyster
||Bonamiosis due to the intrahaemocytic protistan parasite Bonamia ostreae is a European endemic disease affecting flat oysters Ostrea edulis. The parasite has been described in different ecosystems from estuaries to open sea and no clear correlations could be demonstrated between the development of the disease and environmental parameters such as temperature or salinity. The parasite life cycle, including its survival outside the host is not completely known. Nevertheless, the infection can be directly transmitted by cohabitation between infected and non infected oysters suggesting that the parasite does not need intermediate host to complete its cycle. In the present study, the impact of temperature and salinity on the survival of purified parasites maintained in sea water was investigated by flow cytometry. Purified parasites were incubated in three different 0.22 filtered sea water medium (artificial sea water; natural sea water from La Seudre Charente Maritime, France; underground salty water) and were subjected to three temperatures (4, 15 and 25Then, purified parasites maintained in underground salty water were subjected to a range of salinity (5, 15, 20, 25, 30, 35, 40 and 45 g/l). Parasites were collected after 12, 48 hours and 1 week of incubation for flow cytometry analyses including estimation of parasite mortality and non specific esterase activities. All experiments were performed three times. The parasite showed a significant higher survival in underground and natural sea water compared to artificial medium. Parasite survival and non specific esterase activities were lower at 25than at 4or 15High salinities (35, 40 and 45 g/l) appeared to favour parasite survival and esterase activities (Fig. 1). No significant variation of parasite survival could be identified between 12 and 48 h after incubation starting. After one week, parasite cells appeared generally too damaged to allow good cytometry result interpretation. However, up to 58% of parasite survival could be observed after one week in underground salty water at 15.