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PLANARIA-003-2400-Bilateral-Symmetry.jpg

This Week' Photograph October 6, 2013<br />
Whole mount of large common flatworm, Planaria sp.,a turbellarian or platyhelminth.  This specimen exhibits excellent bilateral symmetry through split coloring via Photoshop. Original is stained with a combination of carbon black, showing the digestive intestines, and carmine for the red staining. Planaria are non-parasitic, fresh water free living flatworms of the group Turbellaria.  Its blunt head is on the left side and its pointed tail on the right and exhibit bilateral symmetry. The head is characterized by two light sensitive eye spots and ear-like flaps known as auricles. The mouth is on the right side end of the pharynx; a short muscular tube; seen here sheathed inside the body cavity. Food and waste passes through the pharynx. They are carnivorous and even cannabalistic. The branched vine-like areas in the body surrounding the pharynx is the instestine.  Planarians prefer cool even cold fresh water. They are hermaphroditic and lay two types of eggs; thin shelled transparent summer eggs and thick cocoon like winter eggs.  They also reproduce by transverse division of the body just behind the pharynx.
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