Flat Worms

or Platyhelminthes.

Intro

Flatworms are bilateral invertebrates. They are also acoelomates, (No body cavity).

Platyhelminthes are seperated into Turbellaria, which are non-parasitic creatures.

Flatworms are mainly predators living in water or dark, humid areas.

The most common type of flatworm is the Tapeworm. The tapeworm is a parasitic flatworm, the only parasitic Platyhelminthes.

Ancestry

Platyhelminthes are derived from Platyzoa and all the way back to Bilateria. The oldest known Platyhelminthes fossil is from the Eocene age.

3 different Classes;

1) Terbullarians (Planarians)

2) Trematoda (Flukes)

3) Cestoda (Tapeworms)

Structure

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Reproduction

All flatworms are hermaphroditic, that means they all have penises. They reproduce using a method called 'Penis Fencing'. In Penis fencing, the two flatworms 'fence' using their penises. They go until one penetrates the others skin and impregnates the loser. These battles last around an hour. They can also reproduce using Fission.

Life Cycle

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Movement

Platyhelmenthes move using 2 techniques;

1) Cilia, which help them glide along the floor.

2)Muscle Cells, which help them twist.

Diet

Most Platyhelmenthes are carnivores or scavengers.

Other parasitic platyhelmenthes feast on blood.

And some platyhelmenthes don't eat, but absorb nutrients directly.