Platyhelminthes (+Xenacoelomorpha) Flashcards
what “class” is within Platyhelminthes?
Turbellaria
what orders are within Turbellaria?
- Polycladida (has a multi branched gut)
- Tricladida (has three branched gut)
- Rhabdocoela (simple gut)
how do Platyhelminths get rid of waste?
entry and exit through mouth
what are common traits among all Platyhelminths?
- no coelom
- flat body plan
- no blood vessels
- triploblastic (ectoderm, mesoderm, endoderm)
- incomplete digestive tract
- elaborate reproductive system
what reproductive system are Platyhelminths?
simultaneous hermaphrodites
how do protonephridia work in Platyhelminthes?
- extracellular fluid from mesochyme enters flame cell
- cilia beats and current passes primary urine through for reabsorption
- final urine exits through nephridiopore
what is the phylum formally considered apart of Platyhelminthes?
Xenacoelomorpha
what groups are within Xenacoelomorpha?
Acoela
Xenoturbellida
what is the difference between Xenocoelomorpha and Platyhelminthes?
Xeno = no nephridia or anus (never had either)
Platy = nephridia but no anus (secondary loss)
what does the 4d cell develop into from spiral cleavage in Turbellarians?
gonads, nephridia, mesenchyme, muscle
(note: not coelom)
what is unique about a flatworm mouth?
located ventrically and towards middle of body versus at the anterior end
compare the proboscis of Tricladida, Polycladida and Rhabdocoela
Tricladida = folded in straight (pierces when extended)
Polycladida = multiple folds when relaxed (pierces when extended)
Rhabdocoela = bulbous (grabs and sucks in food when extended)
What structure is connected to the gut and what is its function?
pharynx extension that serves for food collection
