[Coral-List] Diadema 1984 St. Croix

[John Ogden]

Hi Listers, Gene and Bill,

Your interchange reminded me of observations of Diadema we made in St. Croix in 1984, towards the end of the first mass mortality.   I haven't seen any of the following mentioned either during the mortality or in the present days discussion.

The first sign of "infection" in Diadema was sticky spines, presumably from tissue breakdown in the epidermis, picking of bits of sediment and floc from the water.  These "sticky spines" (Fig 1) were  attractive to fishes especially damselfish and wrasses.  As the fish bit the spines they broke off and the net result was a Diadema with a crew cut (Fig. 2).   Once the more delicate distal ends of the spines were broken off they appeared to be no longer attractive to fishes and you could see that recovery and regrowth of the spine was quickly in progress (look closely at Fig 3).

I agree with you that observations like this, especially accompanied by photos, are potentially important in enriching what we know about events like the mortality and may provide important clues is resolving cause, effect and potential recovery following a mortality.

Cheers all, John