Platyhelminthes Flashcards
What are Platyhelminthes?
Flatworms
Name the four classes of Platyhelminthes
Tubellaria - aquatic, 4500 species, body covered in cilia Monogenea - no oral sucker, ectoparasitic, 1100 species, Trematoda - oral sucker, body covered in tegument, endoparasitic, 1100 species Cestoda (Tapeworms) - no digestive tract, 3400 species, endoparisitic, segmented
How do Tubellaria move?
Juveniles glide via ciliary movement and adults via undulations of flanks
How do Trematoda move?
Flukes move slowly through their host via muscular action
How do cestoda (tapeworms) move?
Very little movement
Describe a Platyhelminthes’ digestive system
Most have a simple two branched gut Food is sucked through the mouth Faecal matter is also excreted through the mouth Liquid waste is exreted through the cell wall pores
Describe a Platyhelminthes’ excretion and osmoregulation system
Protonephridia connected to networks of collection tubules leading to nephridiopores. 1) Beating cilia cause a current, and fluid is filtered as it passes through 2) Removes excess water but retains ions 3) Tube cell opens through a nephridiopore to the external environment
Describe Tubellarias nervous system
Brain and a number of nerve cords. Eyespots - pigment cup holds retinular cells They have tactile receptors, chemoreceptors and baroreceptors
Describe Monogenea’s reproduction and lifecycle
‘Monogenea’ means ‘one generation’ i.e direct lifecycles They are hermaphrodites but generally cross fertilise when undergoing sexual reproduction Adults are sessile HYPERVIVIPARITY (Nature’s Russian Doll) 1) Juvenile grows inside immature parent 2) After birth, the parent makes new offspring parthenogenetically, or after maturation, sexually 3) Born juvenile finds a new host and becomes parent
Describe a Trematodes reproduction and lifecycle
Asexual/Sexual depending on species Often alternate asexual/sexual phases Most are hermaphrodites and can cross fertilise
Describe a Cestoda’s reproduction and lifecycle
