Abstract
Field and in vitro studies have shown that high salinities and temperatures promote the proliferation and dissemination of Perkinsus marinus in several environments. In Brazil, the parasite infects native oysters Crassostrea gasar and Crassostrea rhizophorae in the Northeast (NE), where the temperature is high throughout the year. Despite the high prevalence of Perkinsus spp. infection in oysters from the NE of Brazil, no mortality events were reported by oyster farmers to date. The present study evaluated the effects of salinity (5, 20 and 35 psu) and temperature (15, 25 and 35 °C) on in vitro proliferation of P. marinus isolated from a host (C. rhizophorae) in Brazil, for a period of up to 15 days and after the return to the control conditions (22 days; recovery). Different cellular parameters (changes of cell phase's composition, cell density, viability and production of reactive oxygen species) were analysed using flow cytometry. The results indicate that the P. marinus isolate was sensitive to the extreme salinities and temperatures analysed. Only the highest temperature caused lasting cell damage under prolonged exposure, impairing P. marinus recovery, which is likely to be associated with oxidative stress. These findings will contribute to the understanding of the dynamics of perkinsiosis in tropical regions.
Highlights
Protozoa of the genus Perkinsus are facultative intracellular parasites of marine molluscs, in particular bivalves (Choi and Park, 2010; Villalba et al 2011)
In the light of the above information, the present study aimed to evaluate the effects of salinity and temperature on the in vitro proliferation of P. marinus isolated from C. rhizophorae oysters in Brazil
The present study was the first to evaluate the effects of these two abiotic conditions on the physiology of P. marinus isolated from a Brazilian native host
Summary
Protozoa of the genus Perkinsus are facultative intracellular parasites of marine molluscs, in particular bivalves (Choi and Park, 2010; Villalba et al 2011). This genus is widely distributed worldwide and consists of seven species. Perkinsus spp. cells are generally present at the trophozoite phase when cultured in vitro Throughout their development, under controlled conditions, trophozoites increase in size and subsequently undergo schizogony, which is characterized by successive internal cell divisions, with the formation of smaller cells that will generate new trophozoites (La Peyre et al 1993; Sunila et al 2001; Casas et al 2008). Some isolates present zoosporulation under these conditions; this event is often restricted to a small percentage of the cell population (Dungan et al 2007; da Silva et al 2013)
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