[Coral-List] sexing adult Diadema antilarum

[Martin Moe]

Hi Betsy,
"Is there a way to sex adult  *Diadema antillarum *in the field?"
Not really, The only way I have found to sex them is to induce them to spawn and then the difference between eggs and sperm is obvious. After that physical separation is necessary to keep them separate. Sometimes, once the product of the spawn has been observed, it is possible to observe and record some physical characteristic such as number and arrangement of  different spine colors or size and then, at least for a while, it is possible to recognize some of them as males and females. Sometimes it is possible, if they are gravid, to get them to spawn on the reef by gently disturbing with a prod or poke or moving them a bit. Then they can be collected as known males or females. 

One thing I have not tried but might work would be to bring them to the boat and stimulate them to spawn by placing them in a bucket of warm water, about 5 C above ambient. I spawn them in the lab by moving them from ambient temperature, usually around 25 to 26 C, and placing them in a tray of warm water, about 30 C. If they are "ready" they will spawn within sometimes 3 or 4 minutes, but usually the males spawn first, usually within 5 minutes and the females may also spawn quickly but usually after the males by 10 to 15 minutes. If adults are abundant at one location, this could be done, if they are carefully handled, on the boat and then the required number of males and female selected and kept and the others returned to the reef. I think that for a brood stock, 3 or 4 males and about 8 females would be very adequate to maintain a spawn ready brood stock at 25 to 27 C  year round. 

Martin
 

    On Thursday, January 26, 2017 7:36 AM, Elizabeth Sherman <sherman at bennington.edu> wrote:
 

 Hi reefers

Is there a way to sex adult  *Diadema antillarum *in the field?

Betsy

-- 
Elizabeth Sherman, Ph.D.
Biology
Bennington College
website: http://faculty.bennington.edu/~sherman/
*Save the world. Save a Coral.*
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