[Coral-List] Re: Meandrina meandrites Bleaching, Boynton Beach, FL

McCarty and Peters McCarty_and_Peters at compuserve.com
Tue Oct 5 21:46:44 EDT 2004

The report of annual bleaching in Meandrina brings to mind an observation I
made years ago when Judy Lang brought a group of us to Lee Stocking Island
to examine colonies of the brown morph of Porites astreoides that had been
observed to bleach in the fall every year, then recover. We collected a few
bleached specimens for histopathological examination. The tissues were
devoid of zooxanthellae, but still in good condition.  However, in many
areas of the gastrodermis there were oocysts and released sporozoans of
coccidia, the apicomplexans Steve Upton and I had described from corals
(Gemmocystis cylindrus, J. Invertebr. Pathol. 47:184-193, 1986).  The
coccidia were first discovered in coral samples that had bleached patches
of tissue and they specifically infect gastrodermal cells.

We did not have an opportunity for further sampling, but I've always
wondered whether the coccidia were there because the coral had bleached and
its immune system was damaged, therefore allowing the coccidia to easily
infect the cells OR was there something about the life cycle of the
coccidia such that they infect the coral gastrodermis every autumn to
complete their life cycle, causing temporary displacement of the
zooxanthellae, then the symbiosis recovers after the coccidia have been

I mention this because the vast majority of coral bleaching incidents have
not been examined using histological techniques and we might be missing
something by not doing this.  I hope that someone will be able to collect a
few samples from these annual bleaching corals someday over the course of a
few years for histopathological examination. The bleaching of corals
continues to present variations that suggest we still have much to learn
about the causes of bleaching and modes of recovery.

Esther Peters, Ph.D.

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