Origin
Sea urchins (Echinus melo) belong to the Echinodea class. Also called echinde are marine echinoderms animals with spherical body covered with spines.
They can be found in all seas and oceans. They are related to starfish, and sea cucumbers.
Echinodermate in Greek means thorny skin.
Specifically the term sea urchin refers to regular equinoxes that are symmetrical and globular.
Feeding sea urchins
Sea urchins feed mainly on algae, but they can also feed on a wide range of invertebrates such as mussels, sponges, crinoids, etc.
Sea urchin is the favorite food of sea otters.
If left unattended by biologists, they can cause serious damage.
Appearance sea urchin
Sea urchins vary in size from 6 cm to 30-40 cm. Like starfish, they have a symmetry called pentamerism. They have 5 roughly spherical bodies of different sizes radiating at the central axis.
Their body shape sometimes varies to oval shape with degree of bilateral symmetry. Due to the activity the lower part is slightly flat, and the upper part can be slightly bulging.
This irregular shape has evolved to allow animals to penetrate the sand or other accessible places. Internal organs are covered with a thin layer of dermis and spiderma.
Sea urchins have five pairs of estern gills located around the mouth that constitute the main breathing organs.
The lower part, the one that meets the ground contains the oral cavity. The spines are long and sharp to protect the animal's body from predators.
It is not entirely clear, but it seems that in some species these spines contain venom. Common sea urchins have spines 1-3cm long and 1-2mm thick.
In the Caribbean there are sea urchins that have spines ranging in length from 10 to 30 cm.
Behavior sea urchin
At first glance the sea urchins seem incalculable to move. The most visible sign that they are alive is given by thorns.
Most direct their thorns to the touch point to fend off potential predators. Hedgehogs have no eyes in sight, legs or other means of locomotion, but they can move freely on hard surfaces with the help of thorns.
The nervous system has a relatively simple appearance. He has no brain. The nerve center consists of a ring of numerous fine nerfs that surrounds the oral cavity on the inside.
They are sensitive to touch, light and chemicals.
Breeding sea urchins
In most cases the eggs float freely in the sea water, but some species keep them between the Thorns thus providing protection.
The fertilized egg develops in less than 12 hours. Initially appears a ball of cells that turns into a larva.
The Larva has an elongated shape and does not need to feed.
It may take several months for the larva to develop.
First it begins with the formation of the outer surface around the mouth and anus that are almost in the same area. Some species reach maturity after 5 years.
