Dugesia or Planaria are mostly free swimming, non-parasitic flat worms.
Phylum – Platyhelminthes
Class – Tuberllaria
Genus – Dugesia.
Habit and Habitat:
Duge sia is a non-parasitic or free living flatworm. It lives in fresh water ponds or streams. It is also found in vegetation. They are carnivorous that prey on smaller animals and feed on carrion (dead animals) and they are also canibalistic.
Dugesia has an elongated, thin flattened, bilaterally symmetrical body. It grows upto 2 mm long. There are two ends in the body. Anterior end is blunt while the posterior end is tapering. The dorsal surface is convex and the ventral surface is flat. The body is ciliated which help in locomotion. Body is divided into two parts namely a head and a trunk. The head is triangular in shape and has two latterall projections called auricles.
The head bears a pair of eye spots on the dorsal surface. Mouth is situated in the middle of the body on the ventral surface. Through the mouth, the probosis or pharynx protrudes. Behind the mouth there is a small opening called genital aperture. There are numerous excretory pores on the dorsal surface. These are called nephridiospores. Anus is absent from planaria. The planaria has high power of regeneration.