Lecture 18: Helminthes and Annelids Flashcards
In the first clade Bilateria, what are the characteristics?
- bilateral symmetry
- varying degrees of cephalization
- triploblastic
in the clade Lophotrochozoa, what are the characteristics?
- includes 18 phyla
- range from morphologically very simple (ex: flatworms) to morphologically and behaviourally very complex (ex: octopuses)
The first group in lophotrochozoa is phylum platyhelminthes. What is their characteristics?
- Flat worms
- Acoelomates (no coelom)
- triploblastic, but no fluid filled body cavity
- solid tissue
- no circulatory or gas exchange system therefore they breathe by diffusion through the surface of their skin
- incomplete digestive system (waste comes out of mouth)
in the phylum platyhelminthes, what are the characteristics of the class turbellaria?
- free living flatworms
- freshwater and marine
- mostly predatory
- eye spots and ‘brain’ (ganglia)
- surface of body covered in cilia (motility)
- no anal opening
in the phylum platyhelminthes, what are the characteristics of the class Cestoidea?
- tapeworms
- endoparasites meaning they are in the digestive systems of other animals
- mostly vertebrates, but invertebrates can act as intermediate hosts
- lack digestive system
- absorb nutrients through thin body wall
- no mouth and gut
- front end of body modified for holding onto hosts gut
What is there to know about a tapeworms complex life cycle?
- needs 2+ hosts to complete life cycle
- eggs consumed by intermediate host (IH)
- develop into larvae the encysts in tissue of IH
- intermediate host is eaten by definitive host (DH)
- larvae develop into adult tapeworm in gut of DH
- Intermediate host: when a parasite undergoes asexual reproduction (usually invertebrate)
- Determinate host: when a parasite undergoes sexual reproduction
in the phylum platyhelminthes, what are the characteristics of the class Trematoda?
- Dorso-ventrally flattened, no body cavity
- “flukes” w/ 2 large suckers (attachment)
- feed on host tissue or blood
- no anus (waste goes through mouth)
- various shapes and sizes
- simultaneous hermaphrodites
- complex life cycle: 2 or more hosts
- invertebrates serve as intermediate hosts
What does phylum Annelid refer to?
worms, leeches
what are the characteristics of annelids?
- segmented
- Eucoelomates
- closed circulatory system
- gas exchange via diffusion
- complete digestive system w/ anus
Polychaeta is the first class in phylum annelid. What are their characteristics?
- Almost entirely marine
- body segments w/ fresh lobes (parapodia which help it move)
- clearly differentiated head w/ sensory antennae
sedentary species: rarely move, but can if necessary
errant species: actively move, parapodia and head better developed
Polychaetes characteristics continued…
- Errant polychaete are usually predatory
- sedentary polychaetes…
- suspension feed: filter food particles out of the water column
- Deposit feed: trail sticky tentacles over substrate and licking off adhering matter
- usually dig burrows or contract tubes
- free spawning meaning eggs and sperm release into water and fertilization occurs outside the body
Class oligochaete is the 2nd class in the annelid phylum. what are their characteristics?
- much less diverse than polychates
- lack both parapodia and well developed head
- few chaetae
- terrestrial and fresh water species
- most feed by ingesting substrates and digesting organic matter
- simultaneous hermaphrodites
- direct development (no larvae stage)
class hirudinea is the 3rd class in the annelid phylum. what are their characteristics?
- leeches
- mostly freshwater, some marine
- very closely related to oligochaete
- lack parapodia, have clitellum
- Lack chaetae (bristles)
- instead use 2 suckers for locomotion and move by ‘looping’ like an inchworm
Hirudinea characteristics continued…
- predators of soft bodied invertebrates
- some feed on blood of invertebrates (fish, waterfowl, turtles, mammals
- saliva has anaesthetic, anticoagulant and antibacterial properties
