In an earlier blog post ("A weekend in Batangas", 7/3/07) I mentioned that several guests at a resort in Anilao, Batangas where I went for a swim were "attacked" by sea urchins.
What are sea urchins? Here is a brief explanation from Wikipedia, the free encyclopedia (source: http://en.wikipedia.org/wiki/Sea_urchin):
"Sea urchins are small spiny sea creatures of the class Echinoidea found in oceans all over the world. (The name urchin is an Old English name for the round spiny hedgehogs sea urchins resemble.) Their shell, which is also called the test, is globular in shape and covered with spines. The size of an adult test is typically from 3 to 10 cm.
Typical sea urchins have spines that are 1 to 3 cm in length, 1 to 2 mm thick, and not terribly sharp. Diadema antillarum, familiar in the Caribbean, has thin spines that can be 10 to 20 cm long. Common colors include black and dull shades of green, olive, brown, purple, and red.The spines, which in some species are long and sharp, serve to protect the urchin from predators. The spines can inflict a painful wound on a human who steps on one, but they are not seriously dangerous and it is not clear that the spines are truly venomous."