5. ASSOCIATES OF THE LIVING CORAL 



CORALS ARE NOT the Only reef builders or 

 inhabitants of coral reefs. There are an 

 amazing variety of other living creatures as- 

 sociated with them, some of which build up 

 the limestone formation while others are ac- 

 tive in tearing it down. 



Living in the coral rock itself are found various bur- 

 rowing or boring animals, which may so riddle it with 

 holes and passages that the rock may break apart. Cer- 

 tain encrusting sponges, yellow, lavender, purple or red 

 in color are found on the surface of the rock or of sea 

 shells and one of these, Cliona, eats its way into it 

 through small processes. Other sponges with great va- 

 riety in shape and color are attached to the surface of 

 coral rock. 



Certain strange worm-like creatures, the gephyrids, 

 form burrows and are only seen when the coral is 

 broken apart. 



The spiny sea urchins or sea eggs, spherical or ovoid 

 in shape and covered with spines, possess chisel-like 

 teeth which enable them to eat pockets out of the rock. 

 Among these is the long black spined sea urchin, Cen- 

 trechinus antillarum. A smaller species, more ovoid in 

 shape, with shorter purple spines is Echinomeira lucun- 

 ter. Still another sea urchin has fewer spines which are 

 short and thick so that it is appropriately called the 

 club spined urchin, Eucidaris tribuloides. 



Some of the sea shells have adopted a burrowing 

 form of life, including Pholas, Qastrochaena and £itho- 

 phaga. Associated with the coral by attachment, but 



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