AD Flatworms Flashcards
What phylum do flatworms belong to?
Platyhelminthes
Describe free living parasites
Class: Turbellaria Predominately aquatic or as interstitial fauna among wet rocks / sand or below logs and leaf detritus body covered by ciliated epidermis, may be polyphyletic
Describe obligate parasites
Class: Monogenea, Trematoda, Cestoda
Class: Monogenea : Fish and amphibian ectoparasites Monogenetic flukes, covered by tegument Single host usually oral sucker reduced or absent pro and opist haptors present ecto parasitic
Class: Trematoda : Parasitic flukes Digenetic flukes body covered by tegument, one / more oral suckers, haptors absent???? two or three hosts endo parasitic
Class: Cestoda : Tapeworms covered by tegument scolex and strobila of proglottids (“segments”) digestive tract absent two / three hosts endoparasitic
Describe a Planarian’s Circulation and Gas Exchange
No specialized circulatory structures: diffusion limited
Describe the Excretion and osmoregulation of Platyhelminthes
Platyhelminthes are simplest organisms to have a dedicated excretory-system
Osmoregulation-activities-are-undertaken
by-flame-cells-or-protonephridia
Beating-cilia-cause-a-current-–
fluid-is-filtered-as-it-passes-throughthe-cell
Removes-excess-water-but-retains-essential-ions
Tube-cell-opens-through-a-nephropore to-the-external-environment.–
Absent-or-reduced-in-marine-species-as-no-need-to-get-rid-of-water
The reproductive system is most prominent in what class of flatworms?
Parasitic
Is the digestive system more prominent in free living or obligate parasites?
free living
Describe a parasite’s gut
Most parasitic forms have a simple two branched gut
Some phylogenetic studies suggests that the gut has been diminished or lost in parasitic species
Cestodes have no gut at all – absorb nutrients directly
through tegument
Describe a flatworms’ digestive system
Food may be sucked in through the mouth or the pharynx
everted (cillia and digestive cells on surface)
Faecal matter is also excreted through the mouth
Liquid waste is excreted through the cell walls pores
Describe Reproduction in the Turbellaria
Can undergo both sexual and asexual reproduction
Sexual reproduction: animals are hermaphrodites
Asexual reproduction by fission/budding
True or false?
Planaria can be cut into small pieces and regenerate into a whole new organism
True
Describe reproduction in the monogenea
Mono = one
So one generation ie a direct life cycle
Hermaphrodites but generally cross fertilise when undergoing sexual reproduction
Describe the class Monogenea
Hermaphrodites
Parasites mostly on fish skin/gills
Few parasitise bladder
Adults generally sessile but there can be limited movement on host
Describe Reproduction in Class Trematoda Subclass Digenea
Both sexual and asexual depending on species Many species of Digenea have multiple asexual phases Often alternate their sexual and asexual phases in different hosts Most species in this class are hermaphrodites and can cross fertilise Schistosomes are dioecious (separate male and female)
Why are flatworms ecologically and economically important?
Free living flatworms an important part of marine
freshwater and terrestrial ecosystems
In marine systems they can make up as much as 25% of
the meiofauna
The New Zealand flatworm are predators which are invasive in Europe and threaten earth worm populations
This threatens soil integrity and food security
Planarians are important in stem cell science
Parasitic species are of importance in medical, vetinary and wildlife studies
33.5 million people were treated for schistosomiasis in 2010 according to WHO
