Lophotrochozoa II - Flatworms Flashcards
Commissural fibres
Axons that connect the two hemispheres of the brain
Describe the nervous system of flatworms?
Two nerve chords
Transverse commissures linking the two nerve chords (sideways link)
Sense organs and integration at front
What features do flatworms lack that are seen in other bilateria?
SCARAB
No body cavity (coelom)
Therefore no hydrostatic skeleton (limits power of locomotions)
No blood system
No skeleton
No appendages
No anus (food and waste same opening)
No gills or respiratory organs - means oxygen must reach cells by diffusion only so the flatworms are flat and small
Simple is not
Simple doesn’t mean they are primitive (they might have just lost characteristics over time and that’s why they are simple rather than they are simple because they are an old ancestor)
Which superphylum do through guts exist in?
Ecdysozoa
Lophotrochozoa
Deuterostomia
Flatworms lack of anus
Not because they are primitive
Lack of anus was secondarily (lost)
Polyclad
Marine flatworm
Triclad or planarian
Freshwater flatworms
Monogeneans
Flukes with one host
Trematodes
Flukes with more than one host
Cestodes
Tapeworms
Name three parasitic flatworms
Monogeneans
Trematodes
Cestodes
Name two free living flatworms
Triclads
Polyclads
How do flatworms move
Cilia on their epidermis which they use to glide along. Also use muscular ripples.
Size of flatworms
1-10mm
What type of gut do freshwater flatworm species have?
Three branches gut
What type of mating do freshwater flatworm species undergo? XX
Reciprocal
What do flatworms hunt?
Earthworms
Which flatworms hunt?
Freshwater (planarians/triclads) hunt worms and snails
Marine species (polyclads) hunt worms and snails
Characteristics of polyclad marine flatworms
Bright colours
Some can swim
Hermaphrodites
Hunters
Characteristics of freshwater flatworms (planarians/triclads)
Hermaphrodite Reciprocal mating No larvae Hunters Three branches gut
Important characteristic freshwater flatworms (planarians and triclads) are known for
Regeneration
How do freshwater flatworms regenerate?
Stem cells called neoblasts are through the body; when sections of the work are amputated these cells are activated and reform the lost tissues.
Why might have planarian regeneration have evolved? XX
Planarians adapt to starvation by shrinking
