June. 20CC 
21 
The coral world. 
gives them large, soft bodies Coral 
polyps take minerals from seawater 
and build a hard, stony wall around 
themselves. The hard wall protects 
their soft bodies, and the mass of these 
walls forms the coral reef 
Cnidarians have stinging 
capsules That is how they catch their 
food. The tentacles around the mouth 
are usually full of stinging capsules. 
In the capsule is a thin rnl!cd-up tube 
which carries poison These tubes also 
have sharp piercing points. When a 
passing small animal touches the 
stinging capsule, it bursts open The 
capsule shoots out the tube; the sharp 
points pierce the prey animal; and 
poison is injected through the tube The 
poison may stun, kill or paralyse the 
prey. Other capsules send out a fine, 
sticky thread that entangles the prey 
animal 
Cnidarian stings are seldom 
dangerous to people. Most 
cnidarians catch tiny pa'y. When we 
touch them, we usually do not feel their 
stings If you run your hand over a sea 
anemone's tentacles, you will get a 
tingling feeling Its poison is not strong 
enough to hurt you. A few jellyfish, 
however, have tentacles with poison 
that is painful to people Usually, these 
jellyfish live in the open sea, far off 
the coast of Kenya; but sometimes a 
storm blows them to shore. Watch out 
for any jellyfish with long, purple 
tentacles. 
Cnidarians are food for many 
marine animals. Parrotfish grazing on 
coral polyps leave scrape marks on the 
hard coral. Huge leatherback turtles 
