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Related FAQs: Sea Urchins, Urchins 2Urchins 3Urchin Identification, Urchin Behavior, Urchin Compatibility, Urchin Selection, Urchin System, Urchin Feeding, Urchin Disease, Urchin Reproduction

Related Articles: Echinoderms, An Introduction to the Echinoderms:  The Sea Stars, Sea Urchins, Sea Cucumbers and More... By James W. Fatherree, M.Sc. Algae ControlNutrient Control and Export

/A Diversity of Aquatic Life

Some Spines Now! Sea Urchins (and Sand Dollars), the Echinoids, Pt. 2

To: Part 1, Part 3, Part 4, Part 5, Part 6

By Bob Fenner

  Echinothrix calamaris

Genus Diadema:

Diadema antillarum, the Long-Spined Urchin. Tropical West Atlantic. 4-8 inch diameters with spines. Come out at night to feed, hide during the day within rock crevices. Younger ones with white banded spines. Cozumel images during the night and a juvenile showing white and black spine banding in Bonaire. 

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Verticals (Full/Cover Page Sizes Available
Diadema mexicanum A. Agassiz 1863, Needle Sea Urchin. Costa Rica (Pacific side) 2011 

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Diadema paucispinum (A. Agassiz 1863), a Long-Spined Sea Urchin. Pacific; Hawai'i and islands of the South Pacific. To about twelve inches maximum diameter, with spines. Usually in 60 or more feet of water on a vertical surface. Common name means "few spines" which you may not agree with if you get poked but good. Kona pix.  


Diadema savignyi (Michelin 1845), a Long-Spined Sea Urchin. Indo-Pacific; Africa to the South Pacific. Test about five inches maximum diameter, with spines to sixteen. Hide in shade by day, scouring the reefs by night. Blue ring around anus is indicative of this species. A frequent contaminant on/in live rock imports. Tiny aquarium individual and Philippines one shown. 


Diadema setosum (Leske 1778), the Hatpin Urchin. Indo-Pacific; Red Sea to South Pacific, Japan. To about four inches in diameter. Useful in coral bearing aquariums as these echinoids avoid their rocks. A frequent "contaminant" on live rock imports. Painful to get stuck by... Red ring around anus and five white dots are definitive. Fiji nighttime image and N. Sulawesi by day. 


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To: Part 1, Part 3, Part 4, Part 5, Part 6

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