Lipid composition of gametes in scleractinian reef-building corals: wax-esters generate buoyancy for the gametes

Abstract

ABSTRACT Most reef-building corals are hermaphroditic and discharge buoyant bundles that contain a mixture of eggs and spermatozoa during the breeding season. The buoyancy of the bundles is due to wax-esters. This study analysed and compared the lipid compositions in eight species of corals. Overall, 60–80% of the total lipid composition of the eggs or embryos of six species, Acropora digitifera, A. florida, A. monticulosa, Dipsastraea lizardensis, Ctenactis echinata, and Pseudosiderastrea tayamai that discharged buoyant eggs was wax-esters. Although Galaxea fascicularis is a dioecious coral, the bundle released from males (or hermaphrodites) contained spermatozoa and pseudo-eggs. Both eggs and pseudo-eggs contained high amounts of wax-esters. In contrast, the wax-ester content in sedimenting eggs released from Oulastrea crispata was very low. Thus, this study confirmed the presence of wax-esters in buoyant egg bundles. This suggests that wax-esters play a role in the dispersal and settlement potential of planula larvae in corals.