Experiments were conducted at Lizard Island on the
Great Barrier Reef (Lat. 14°400S; Long. 145°260E). Eight
live colonies of the reef-building coral A. millepora, each
measuring approximately 30 ´ 30 cm, were collected by
hand from fringing reef crests and maintained in out-
door, ¯ow-through seawater tanks at the Lizard Island
Research Station. Prior to sunset on the night of 9 De-
cember 1998, the individual colony pieces were isolated
in 50 l plastic containers. Synchronous spawning oc-
curred between 21:00±21:30 h. The released gametes, in
the form of buoyant egg±sperm bundles 1±1.5 mm in
diameter, were collected in 250 ml containers from the
water surface by gentle suction through a 7 mm (i.d.)
plastic tube.