parasites on corals

[Bridget Elliott]

We are assuming that infestations by Spirobranchus are not advantageous to
the corals, which I know is problematic.

However, Acropora tends to form a "lump" around the worm holes, which would
consume energy that could have been used for growth/reproduction. Holes in
the coral plates may also weaken the structure, and make them more
susceptible to breakage. (but on the other hand, the worms may set up
currents that facilitate the bringing of food to the coral polyps).

Presumably a worm larvae landing on a healthy coral would be consumed by the
coral. This leads to the assumption that only larvae that land on a "dead"
or damaged spot would be successful in boring into the coral. This has been
suggested by some authors, eg. Marsden 1993 who proposed that damage to
Millepora blades could be an entry site for Spirobranchus worms.


----- Original Message -----
From: Julian Sprung <JSprung at compuserve.com>
To: Bridget Elliott <b.elliott at mweb.co.za>
Sent: 06 November, 2000 3:21 PM
Subject: parasites on corals


Gee that would be difficult to separate from other environmental factors.
For example, perhaps the polychaetes have better food supply in the same
habitat where the diver impacts are greatest. Why should the corals be
stressed to become infested with the worms?

Julian Sprung

--------------
Dear all

An MSc student investigating parasitism/mutualism of polychaete worms
(Spirobranchus) on Acropora plates at Sodwana (South Africa), to see if
they can be used as an indicator of reef health. We are battling to find
references that refer to any kind of data on this phenomenon, and have only
been able to find mostly anecdotal info.

She is hypothesising that areas that are shallower and with higher diver
number will be more stressed, and thus will have a greater degree of
infestation of Spirobranchus. Plates that occur deeper should have fewer
parasites (less storm damage and fewer divers), as should less dived sites.

Has anyone come across any information (even unpublished reports) about the
effects of Spirobranchus or other creatures on coral health (does they
perhaps retard coral growth), or any reports that have sucessfully linked
damage to numbers of parasites or other bioindicators ?

Many thanks
Bridget Armstrong
KwaZulu-Natal Nature Conservation Service
South Africa