In vitro effects of temperature and salinity on fatty acid synthesis in the oyster protozoan parasite Perkinsus marinus

The effects of temperature and salinity on fatty acid synthetic activities in the oyster protozoan parasite, Perkinsus marinus, were tested in vitro at 10, 18 and 28 jC in a salinity of 28 psu and 14, 20 and 28 psu at a temperature of 28 jC using C sodium acetate as a substrate. Salinity treatments exhibited few treatment effects, but temperature significantly affected cell proliferation, fatty acid content and fatty acid synthesis rates. Fatty acid synthesis rates increased approximately two-fold for every 10 jC increase in temperature; however, the predominant fatty acid synthesized differed between treatments. At 10 jC, the synthesis rate for 18:1(n 9) was not significantly different from the 18 jC treatment and weight percent of 18:1(n 9) was higher at 10 than 18 and 28 jC. In contrast, the synthesis rate for 20:4(n 6) was over five times lower at 10 than at 18 and 28 jC, and the percent fatty acid content of 20:4(n 6) was over two-fold lower at 10 than at 18 and 28 jC. Results suggest that further elongation and desaturation of 18:1(n 9) to 20 carbon polyunsaturated fatty acids may be inhibited at low temperatures. These findings may be relevant to field observations that disease progression and virulence of this parasite are correlated to high water temperatures. D 2004 Elsevier B.V. All rights reserved.