Membrane lipid phase transition behavior of oocytes from three gorgonian corals in relation to chilling injury.

The lipid phase transition (LPT) from the fluid liquid crystalline phase to the more rigid gel structure phase that occurs upon exposure to low temperatures can affect physical structure and function of cellular membranes. This study set out to investigate the membrane phase behavior of oocytes of three gorgonian corals; Junceela fragilis, J. juncea and Ellisella robusta,at different developmental stages after exposure to reduced temperatures. Oocytes were chilled to 5°C for 48, 96 or 144 h, and the LPT temperature (LPTT) was determined with Fourier Transform Infrared (FTIR) spectroscopy. The J. fragilis oocytes had a higher LPTT (∼23.0-23.7°C) than those of J. juncea and E. robusta oocytes (approximately 18.3-20.3°C). Upon chilling for 96 h at 5°C, the LPTTs of J. juncea and E. robusta oocytes in the early (18.0±1.0 and 18.3±0.6°C, respectively) and late (17.3±0.6 and 17.7±1.2°C, respectively) stages were significantly lower than those of J. fragilis oocytes (20.3±2.1 and 19.3±1.5°C for the early and late stages, respectively). The LPTTs of early stage gorgonian oocytes was significantly lower than those of late stage oocytes. These results suggest that the LPT of three gorgonian oocytes at different developmental stages may have been influenced by the phospholipid composition of their plasma membranes, which could have implications for their low temperature resistance.