Abstract
Our previous studies have suggested that chilling sensitivity of coral oocytes may relate to their relatively high lipid intracellular content and lipid composition. The distribution of lipids during the oocyte development was determined here for the first time in two gorgonian species (Junceella juncea and Junceella fragilis). The main lipid classes in the two gorgonian oocytes were total lipid, wax ester, triacylglycerol, total fatty acid, phosphatidylethanolamine and phosphatidylcholine. The results indicated that early stage oocytes of J. juncea and J. fragilis were found to have increased lipid content than late stage oocytes. The content of wax ester was significantly higher in the early stage oocytes of two gorgonian corals (51.0±2.5 and 41.7±2.9 µg/mm3/oocyte) than those of late stage oocytes (24.0±1.4 and 30.4±1.2 µg/mm3/oocyte, respectively). A substantial amount of phosphatidylethanolamine and total fatty acid was detected at each stage of oocyte development in two gorgonian ranges from 107 to 42 µg/mm3/oocyte and 106 to 48 µg/mm3/oocyte, whilst low levels of phosphatidylcholine were found in two gorgonian oocytes. The levels of total lipid in the late stage oocytes of J. juncea were significantly higher than those of J. fragilis. The observed differences may partially be related to different habitat preferences as higher lipid levels in J. juncea, a deeper-water coral species exposed to lower temperature seawater, might relate to adjustments of cell membranes in order to increase membrane fluidity.
Highlights
Gorgonian corals are suffering continuing decline in population size and reproductive ability due to environmental stresses such as pollution, habitat destruction and global climate change [1]
Stage oocytes of J. juncea had an average volume of 0.0054 mm3 slightly smaller than that of J. fragilis oocytes (0.0066 mm3)
The main lipid components in the early and late stage oocytes of J. juncea were identified as total fatty acid (36.4% and 58.0%, respectively) followed by phosphatidylethanolamine (36.9% and 23.3%), wax ester (17.7% and 13.1%), phosphatidylcholine (8.9% and 5.5%) and triacylglycerol (,1%)
Summary
Gorgonian corals are suffering continuing decline in population size and reproductive ability due to environmental stresses such as pollution, habitat destruction and global climate change [1]. Cryopreservation technologies are urgently needed to establish conservation measures to preserve coral populations. Cryopreservation of coral sperm has been successful [2]. Chilling sensitivity of coral larvae has been reported to be very high [3]. We have reported that hard coral (Echinopora spp.) and gorgonian coral (J. juncea and J. fragilis) oocytes showed significant levels of chilling tolerance at 5uC and 0uC, these oocytes were very sensitive to chilling at 25uC resulting in a significant decline in ATP concentration after 4 h chilling [6,7]
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