Planarian

Habitat: Freshwater ponds, lakes and shallow rivers

Length: 0.32–2.54cm

Diet: Carnivorous

IUCN red list status: Not evaluated



A planarian is a flatworm with a range from 0.32 cm to 2.54 cm in length that lives in marine or moist terrestrial habitats but most of them inhabit freshwater areas.

They have a triangular head with two eye spots. The mouth is located on the underside of the organism and once the food enters, it goes to the gut that extends to almost all parts of the body. Undigested matter exits by the same spot; planarian has no anus.

Planarians are hermaphrodites, so their reproductive system has both male and female parts. The male part starts by sets of testes connected to a pair of sperm ducts. The female part consists of two ovaries that lead to two oviducts. The genital atrium receives products from oviducts and sperm ducts. It also receives sperm from the other planarian. Planarians has two seminal vesicles that unite and open again to the genital atrium.

The nervous system is composed of a rudimentary brain and two lateral nerve cords with transverse connections that relay messages through the body.

The excretory system consists of excretory cells called Protonephridia or flame cells and a system of excretory tubules.