Diadema antillarum

[James C. Hendee]

The following message, orginally posted to the marine biology list-server  
(marbio), might be of interest to coral-listers interested in the  
dynamics of Diadema populations on patch reefs: 

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From: John Ogden <jogden at marine.usf.edu> 
Date: Wed, 10 Jul 1996 15:35:26 -0400 (EDT) 
Subject: Re: marbio: Diadema antillarum 

Dear Mr Sosa: 

It was interesting to get your message and to recall that in spite of the 
widespread mass mortality of Diadema in the western Atlantic in 1983-84, 
they did not die in the eastern Atlantic. 

We did many Diadema removal experiments from patch reefs in the early 
1970's at the West Indies Laboratory in the Virgin Islands.  They were 
kept from moving into cleared areas with difficulty so it was helpful to 
choose a patch reef rather remote from controls.  At any rate, the results 
of removal experiments were always dramatic, algae virtually sprang 
from the reef surface, often smothering corals.  In one case, a cleared 
patch reef did not "recover" (that is, recolonize with Diadema) for many 
years.  Our theory was that the algae that covered the cleared reef 
prevented the recruitment of juveniles by mechanical interference, and 
prevented adults from moving back by interfering with their ability to 
hold on by wedging their spines into reef cracks.  Another urchin, 
Tripneustes, moved up from surrounding seagrass beds onto the cleared 
reefs.  This urchin using its tube feet to grab vegetation to hold on. 

I never liked the taste of Diadema compared to Tripneustes, but they may 
be an acquired taste. 

Best wishes with your work. 

John C. Ogden        Director        Phone:  813/893-9100 
Florida Institute of Oceanography    Fax:    813/893-9109 
830 First Street South               St. Petersburg, Florida 33701 

On Mon, 8 Jul 1996, Nicolas Sosa wrote: 

> Here, in the Canary Islands, the sea urchin Diadema antillarum is extremely  
> abundant. In some places, a density greater than 10 individuals per square  
> meter has been reported. It is assumed (but not verified) that this is due  
> to overfishing of its natural predators.  
>  
> A group of students of the University of La Laguna would like to perform two  
> experiments: 
>  
> 1. Eliminate all the individuals in a well delimited zone, to monitor the  
> recolonization process. 
>  
> 2. Investigate commercial exploitation of the urchins. We plan to do some  
> biochemical, bacteriologic and toxicologic analysis as well as biometric  
> measures (i.e. gonadosomatic index, etc). We think of possible uses like  
> food for humans or for fish in aquaculture. 
>  
> Does anybody have any experience with this kind of experiments with urchins? 
>  
> Any help would be greatly appreciated 
>  
> Many thanks in advance 
>  
> Nicolas Sosa 
> Universidad de La Laguna 
> nsg at iac.es 
> Tel: 34 22 60 53 21 
> FAx: 34 22 60 52 10 
>  
>  


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From: Mike Marshall <marshall at marinelab.sarasota.fl.us> 
Date: Wed, 10 Jul 1996 21:51:38 -0400 (EDT) 
Subject: Re: marbio: Diadema antillarum 

Just wondering if there are any other areas in the Atlantic/Caribbean  
with sizeable populations of Diadema.  Just spent 10 days diving around  
the Miskito Cays of Nicaragua and I didn't see any.  Lots of algae and no  
urchins seemed to be the general condition. 

Mike Marshall 

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End of marbio-digest V1 #209 
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