|
|
The Sea urchins are interesting and
attractive marine creatures that are members of the phylum
Echinodermata family, together with the sea cucumbers, the
crinoids, the starfish and the brittle stars. These
small water creatures have spines that can be sharp and long and that
help the sea urchins to protect from their predators. If
somebody will have the bad luck of stepping on a sea urchin's
spine he/she may be pricked by the spines which will cause a
painful wound. The good news is that the sea urchins are not
really venomous. Only the pedicellariae that are situated
between the spines are venomous. Under the spines, the sea
urchins have a shell that has a globular shape and is also known
as the test. The adult test has a size of 3 to 10 centimeters.
The symmetry of the sea urchins is a fivefold one, which is
typical for the echinoderms and is called pentamerism. The sea
urchins can move due to the hundreds of tube feet which are
adhesive, transparent and tiny. This symmetry can be seen in the
urchin's dried test. The sea urchin mouth is situated on the
oral surface and is made from five jaws or calcium carbonate
teeth. Inside is a fleshy structure, like a tongue. An
Aristotle work gives the name of the sea urchins` chewing
organ, known as the Aristotle's lantern. The sea urchins` color
can be red, black, green, purple, olive or brown, and their diet
is made in principal from algae but they also eat invertebrates
such as crinoids, mussels, brittle stars and sponges. But, sea
urchins are themselves the favorite food for the wolf eels and
for the sea otters. If the sea urchins are left unchecked they
create the urchin barren, destroying their own environment. |
|
