coral sex change? (fwd)

Bruce Carlson carlson at
Sat May 23 19:49:08 EDT 1998

Here's a follow-up on the Sandalolitha spawning that I reported last month
(below).  This coral spawned on April 21,22 & 23 and spawned again on May
15, 16 & 17.  As in April, it produced only sperm (copious amounts!).
This coral definitely produced viable eggs in previous years as we were
able to rear them to the planula stage.  But now it appears to be
producing only sperm.  The second colony in this aquarium has always
produced sperm.  It did not spawn in April but did spawn on May 15 -- as a


Date: Tue, 28 Apr 1998 20:35:03 -1000 (HST)
From: Bruce Carlson <carlson at>
To: Coral-List <coral-list at>
Subject: coral sex change?

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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