Phylum platyhelminthes has four classes:

(a)    Class Turbellaria

  1. They have over 3, 000 species.
  2. They are free-living and aquatic
  3. External surface is ciliated.
  4. They are predators.
  5. They possess rhabdites, protrusible proboscis, frontal glands and many mucous glands.
  6. Mostly hermaphroditic.

Examples: Convoluta,  Notoplana, Dugesia.

(b)   Class Monogenea

1. They have about 1,100 species.

2. They are monogenetic flukes

3. They are ectoparasites on vertebrates.

4. One life-cycle form is present only in one host.

Examples: Disocotyle, Gyrodactylus, Polystoma

(c)  Class Trematoda

1.They have over 10,000 species.

2. They are all parasite

3. They have several holdfast (attachment) devices like stickers or hooks.

4. They have complicated life cycles involving both sexual and asexual reproduction.

Examples: Fasciola (liver fluke)



(d)        Class Cestoidea

1. They have 3,500 species.

2.  They are all parasite

3. They have no digestive tract

4. They produce a large number of reproductive structures.

Examples: tapeworms.

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