coral sex change?

Bruce Carlson carlson at
Wed Apr 29 02:35:03 EDT 1998

In 1982 I collected a Sandalolitha robusta coral in Palau.  In 1992 we
noticed it spawning.  It may have spawned in previous years and went
unnoticed, but since 1992 we have checked for spawning every year.
Spawning usually occurs a few days before the new moon in April at 7:00
am. This is in an indoor aquarium on display to the public.  There are
skylights overhead which is probably how it remains cued in to the phase
of the moon even indoors.

Last year we obtained fertile eggs which developed into planula (there is
a second smaller colony nearby which has always produced sperm). This year
we anxiously awaited the spawning event, cameras in hand and egg collectors
ready.  But instead of eggs, this year it produced sperm!  It spawned 3
days in a row and only produced sperm.  The other male colony did not
spawn this year.

Not sure what to make of this but we will check again in May because
occasionally it spawns over two months.

I haven't checked the literature on sex reversal in fungiid corals, or
corals in general, but would appreciate if others have encountered this
phenomenon in corals.  We definitely have never observed this coral
producing sperm in any of the previous years, and it definitely produced
no eggs this year at all.


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