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Of the 650 species of leech listed, Hirudo medicinalis is one of the most extensively studied. This annelid from the subclass Hirudinea has 2 suckers, one housing the mouth and its 3 jaws. It lives mainly in the stagnant waters of marshes and ponds. When it comes to reproduction, the animal is a hermaphrodite. Inseminated leeches lay their eggs during the spring and summer months, outside the water, with cocoons containing as many as thirty young.
Four main species of sea urchins are distributed along the nearshore waters of Southern California: Lytechinus anamesus (white urchin), Centrostephanus coronatus (coronado urchin), Strongylocentrotus purpuratus (purple urchin), and Strongylocentrotus franciscanus (red urchin).here are ten classes in this phylum. Sea urchins are grouped as Echinoidea. Until recently, there was a clear-cut distinction between Echinoidea and other classes because they possess what was believed to be a unique lantern for mastication.