L7 Platyhelminthes Flashcards
How many body layers?
3, Triploblastic
Do they have a coelom?
No, are acelomates
How is their body structured?
Dorsoventrally flattened, have a simple internal structure, no blood system is required as rely on diffusion.
Cephalisation
Organs present
What symmetry do they exhibit?
Bilateral
Describe the excretory system
Gut has one opening, so mouth and anus. Excretory system is composed of protonephridia and wafting of flagella in flame cells, generating a partial pressure in the tubes, which means fluids are drawn into the protonephridia
What are protonephridia?
a network of dead-end tubules lacking internal openings found in the phyla Platyhelminthes, Nemertea, Rotifera and Chordata. They end in flame bulbs, which each have a flagella
What are the free living flatworms called?
Turbellarians
What are the general features seen in the turbellarians?
- Move using muscle fibres, and undulation
- Coved in epidermis
- Bottom may be lined with cilia for movement
- May secrete mucus so they can glide along
- Possess some simple eyes
- Auricle for detecting chemicals
- Hermaphrodite
- Use a pharynx to eat, digests out of the body
Describe the eyes in turbellarians
pigment cup eyes, detect if light is present, which is essential, as need to stay out of the sun
Describe regeneration in the turbellarians
If chopped up, the platyhelminth can reform a new animal, as cells are pluripotent - rate of regeneration deifiers with position of the cut
What happens if very thin slices of the platyhelminth is left to regenerate?
The segment will lose polarity, and a janus head may form
What was the experiment on Platyhelminthes carried out by Thompson and McCornel in 1950s?
Research into how memory could be transferred chemically. Treated worms with a bright light and electric shock to train them. When cut up and reformed, new worms responded the same as the trained worms. Trained worms were then fed to untrained worms, and looked to see if reacted similarly - suggested results may be bias
How do turbellarians reproduce sexually?
mutual exchange of sperm can occur, however, some species avoid this as it is costly to be female
What is penis fencing?
Fighting during mating of hermaphrodite flatworms, so as not to be fertilised
What are the general adaptations of a parasite?
Loss of unwanted organs Penetration devices Attachment devices Protective devices Transmission via a vector Efficient production of eggs
What are the parasitic flatworms called?
The trematodes(Flukes), and cestoidea(Tapeworms )
What covers the body of a fluke and how does it form?
Tegument, formed by the cuticle, secreted by cells beneath
What is non-ciliated syneitum?
No cell bodies, is a continuous cell unit
Describe reproduction mode of the flukes
Normally hermaphrodite, most of the internal structures are reproductive, can produce 10,000 more eggs than free living flatworms
Explain the fluke lifecycle
Combination of sexual and asexual stages, taking place in various hosts. Adults produce eggs, which travels, as a miracidium, to the first intermediate host, often a snail, where it becomes a sporocyst and develops into media and the cercaria, which are then released from the snail host. These then make their way to the definitive host, where they mature and produce eggs
What are miracidium?
a free-swimming ciliated larval stage in which a parasitic fluke passes from the egg to its first host, typically a snail
What are sporocysts?
a parasitic fluke in the initial stage of infection in a snail host, developed from a miracidium
What are media?
larva produced within the sporocyst of many trematodes that produces another generation of rediae or develops into a cercaria
What are cercaria?
free-swimming larval stage in which a parasitic fluke passes from an intermediate host (typically a snail) to another intermediate host or to the final vertebrate host.
What are blood flukes?
Schistosomatidae adults live in veins of intestines and bladder of host, eggs past into bladder or intestine and excreted. Once released, eggs hatch and make their way into a snail. . Once a cercaria, makes way out of the snail, and burrows into skin of host. Have two separate sexes, adults keep females in a groove until ready to reproduce
What are lancet flukes?
Has a similar lifecycle to blood fluke. Definitive host is cow or sheep. However, have two intermediate hosts, the cercaria developing in an ant. Behaviour of the ant is changed - makes them clamp onto a blade of grass in the day, when cows and sheep are grazing, meaning chance of transmission is increased
What phylum are Platyhelminthes under?
Lophotrocozoans
What are the acelomorpha?
Used to be grouped with platyhelmitnthes, now classed as a separate group
What are eye flukes, diplostomum spatheceum?
Intermediate host is a fish, cause cataracts to form over fish eye, so it becomes more vulnerable to predation, by the definitive host, birds
What are cooperative trematodes?
Some can coordinate and take on differs roles, and defend the colony from other parasites
What are the features of the tapeworms?
Tegument No gut Scolex Strobilia Hermaphrodite
What is the scolex?
Head rejoin, which has hooks and suckers that attach to the intestine wall
What are the strobilia?
proglottids, which make up the rest of the tape worm, made of repeated segments, each containing a complete, sexually mature reproductive system
Describe the lifecycle of a beef tapeworm
Eggs are injected by the intermediate host, cattle. The larvae migrate to the muscles, are then eaten by humans, the definitive host
