50 



DANGEROUS MARINE ANIMALS 



Venom Apparatus of Sea Urchins. The venom apparatus of sea 

 urchins is believed to consist of their hollow venom-filled spines, 

 and the globiferous pedicellariae. However, usually only one or the 

 other is present within a single species of sea urchin." 



Fig. 23. Top: Black long-spined sea urchin, Diadema setosum (Leske). 



Bottom left: Sea Urchin, Toxopneustes elegans Doderlein. Bottom right: 



Sea Urchin, Asthenosoma ijimai Yoshiwara. Part of the outer covering has 



been removed to show the test beneath. (Kreuzinger) 



Spines. The spines of sea urchins vary greatly from group to 

 group. In most instances the spines are solid, have blunt, rounded 

 tips, and do not constitute a venom organ. However, some species 

 have long, slender, hollow, sharp spines, which are extremely dan- 

 gerous to handle. The acute tips and the spinules permit ready 

 entrance of the spines deep into the flesh, but because of their ex- 

 treme brittleness, they break off readily in the wound and are very 

 difficult to withdraw. The spines in Diadema may attain a length 



