Lecture 3 DA Flashcards
How many cell layers do worms have?
Triploblastic
How are worms classified regarding their coelom?
Acolomates
Blastocoelomates
Coelomates
What are blastocoelomates and acoelomates?
Blastocoelomates - gut isn’t mesodermally derived, but has a body cavity. Only the outer wall is mesodermally derived.
Acoelomates - has a solid mesoderm, so no body cavity.
Which phyla of worms are coelomates, acoelomates and blastocoelomates?
Coelomates - Annelida
Blastocoelomates - Nematoda
Acoelomates - Platyhelminthes
Are Platyhelminthes free living or parasitic?
Has both parasitic and free living.
What kind of symmetry do Platyhelminthes have?
Bilateral
Are Platyhelminthes segmented?
No.
What kind of gut do Platyhelminthes have?
Either a blind gut, or no gut.
What kind of shape do Platyhelminthes have?
Theyre flat.
What is the parenchyma?
Is the cellular filling between the epidermis and gastrodermis.
What kind of muscles do Platyhelminthes have (4)?
Longitudinal, circular, oblique and dorsoventral.
What kind of circulatory and respiratory system do Platyhelminthes have?
None, they rely on diffusion.
Are Platyhelminthes hermaphrodites?
Yes.
What fills the blastocoele in Platyhelminthes?
Mesoderm.
What structure do Platyhelminthes have for locomotion?
Cilia on their ventral surface.
What is a protonephridia, and how does it work?
Tubule that runs from the parenchyma to pores on the outside of the body.
Is a blind ended tube, with a flame cell on the end, pore side.
Flame cell has cilia that beat to draw water down the tubule, where its filtered.
An excretory duct removes waste.
What are the classes of Platyhelminthes (4)?
Turbellia
Monogenea
Trematoda
Cestoda
What is the class tubellia considered?
Paraphyletic
What kind of worm are class turbellia classified as?
Free living
Which class are parasitic worms believed to be derived from?
Class tubellia
What water environment do class tubellia live in?
Both fresh and salt water, land as well, if moist enough.
How much nerve development do class turbellia have?
They are cephalised with a complex nervous system.
What kind of sensory organs do turbellia have?
Light receptors and statocysts, as well as chemo and mechanoreceptors.
How do turbellia feed?
Has a muscular pharynx that extends out of the gut and can wrap around prey.
Can also be sticky.
What is the gut of turbellia like?
Can have numerous branches (up to 4), are classified on this basis.
How do turbellia move (3)?
Ciliary gliding - has ventral cilia, and secretes mucus onto substratum, glides across it.
Pedal waves - undulates one side of their body at a time.
Looping - loops head over heels, cartwheels across.
What is the most common mode of locomotion for turbellia?
Ciliary gliding.
How do turbellia have temporary attachment to substrata (3)?
Can have adhesive cilia, excrete adhesive or use pharynx as a sucker.
What is the duo-gland adhesive system?
Used by turbellia for temporary attachment.
Two types of glands ar eburied in the parenchyma, and extend to the epidermis.
One is the viscid gland which secretes sticky mucus.
The other is the releasing gland, which releases a chemical that liquefies it, typically acid.
What are rhabdites?
Capsules are secreted by glandular cells embedded in the parenchyma, and extend to the epidermis.
Absorb water, expand and secrete mucus.
How do turbellia reproduce?
Are monoecious, so to spread sperm, has a penis that is like a stylet, and will fence with another worm to inject sperm. Can have multiple penises.
When a turbellia egg is fertilised, what does it form?
Müller larva.
What proportion of the phylum Platyhelminthes are parasitic?
3/4
What is the ancestral form of parasitic worms?
Free living worms
What have parasitic Platyhelminthes worms lost vs free living ones?
Lost complexity in the nervous system, is uncephalised and reduced.
Are parasitic worms cephalised?
No.
What is a syncytial tegument?
Thick layer with microvilli on the surface.
Are the epidermis of parasitic Platyhelminthes ciliated?
No.
How are epidermal cells attached to one another in parasitic Platyhelminthes?
They are multinucleated, embedded in the parenchyma, but cytoplasm extends out and fuses with each other.
What is the purpose of a multinucleated epidermal cells in parasitic Platyhelminthes (3)?
Thought to defend againt immune cells and digestion, and aid in nutrient transfer.
What are the three parasitic classes of Platyhelminthes, and are they ecto or endoparasites?
Monogenea - ectoparasite
Trematode - endoparasite
Cestoda - endoparasite
How do class monogenea feed?
Are very small, and suck out nutrients from outside the host.
How do monogenea spread?
Reproduce sexually, only produce 1 larva, which swims away to find another host.
How do monogenea hold onto their host?
Hooks on their mouth.
What are the primary hosts of class trematode?
Vertebrates.
What happens in a primary host vs an intermediary one?
They reach sexual maturity in a primary host, whereas an intermediary one is used to spread and reach the primary host.
In the liver fluke (trematode), how many hosts does it have?
3, humans - primary, with fish and snails as an intermediary.
What is digenea?
Having 2 or more hosts.
In the liver fluke, where are ferilised eggs released, what are they eaten by, and what do they develop into?
Released in humans, eaten by snails and develops into larva called miracidium.
What happens to miracidium in snails?
They produce sporocysts via asexual reproduction.
what do sporocysts contain, and what do they contain in them?
They have redia in them.
Redia have cercaria in them, which swim out and infect fish.