L7 Platyhelminthes

Question 1

How many body layers?

Answer 1

3, Triploblastic

Question 2

Do they have a coelom?

Answer 2

No, are acelomates

Question 3

How is their body structured?

Answer 3

Dorsoventrally flattened, have a simple internal structure, no blood system is required as rely on diffusion.
Cephalisation
Organs present

Question 4

What symmetry do they exhibit?

Answer 4

Bilateral

Question 5

Describe the excretory system

Answer 5

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

Question 6

What are protonephridia?

Answer 6

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

Question 7

What are the free living flatworms called?

Answer 7

Turbellarians

Question 8

What are the general features seen in the turbellarians?

Answer 8

• 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

Question 9

Describe the eyes in turbellarians

Answer 9

pigment cup eyes, detect if light is present, which is essential, as need to stay out of the sun

Question 10

Describe regeneration in the turbellarians

Answer 10

If chopped up, the platyhelminth can reform a new animal, as cells are pluripotent - rate of regeneration deifiers with position of the cut

Question 11

What happens if very thin slices of the platyhelminth is left to regenerate?

Answer 11

The segment will lose polarity, and a janus head may form

Question 12

What was the experiment on Platyhelminthes carried out by Thompson and McCornel in 1950s?

Answer 12

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

Question 13

How do turbellarians reproduce sexually?

Answer 13

mutual exchange of sperm can occur, however, some species avoid this as it is costly to be female

Question 14

What is penis fencing?

Answer 14

Fighting during mating of hermaphrodite flatworms, so as not to be fertilised

Question 15

What are the general adaptations of a parasite?

Answer 15

Loss of unwanted organs
Penetration devices
Attachment devices 
Protective devices
Transmission via a vector 
Efficient production of eggs

Question 16

What are the parasitic flatworms called?

Answer 16

The trematodes(Flukes), and cestoidea(Tapeworms )

Question 17

What covers the body of a fluke and how does it form?

Answer 17

Tegument, formed by the cuticle, secreted by cells beneath

Question 18

What is non-ciliated syneitum?

Answer 18

No cell bodies, is a continuous cell unit

Question 19

Describe reproduction mode of the flukes

Answer 19

Normally hermaphrodite, most of the internal structures are reproductive, can produce 10,000 more eggs than free living flatworms

Question 20

Explain the fluke lifecycle

Answer 20

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

Question 21

What are miracidium?

Answer 21

a free-swimming ciliated larval stage in which a parasitic fluke passes from the egg to its first host, typically a snail

Question 22

What are sporocysts?

Answer 22

a parasitic fluke in the initial stage of infection in a snail host, developed from a miracidium

Question 23

What are media?

Answer 23

larva produced within the sporocyst of many trematodes that produces another generation of rediae or develops into a cercaria

Question 24

What are cercaria?

Answer 24

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.

Question 25

What are blood flukes?

Answer 25

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

Question 26

What are lancet flukes?

Answer 26

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

Question 27

What phylum are Platyhelminthes under?

Answer 27

Lophotrocozoans

Question 28

What are the acelomorpha?

Answer 28

Used to be grouped with platyhelmitnthes, now classed as a separate group

Question 29

What are eye flukes, diplostomum spatheceum?

Answer 29

Intermediate host is a fish, cause cataracts to form over fish eye, so it becomes more vulnerable to predation, by the definitive host, birds

Question 30

What are cooperative trematodes?

Answer 30

Some can coordinate and take on differs roles, and defend the colony from other parasites

Question 31

What are the features of the tapeworms?

Answer 31

Tegument
No gut
Scolex 
Strobilia
Hermaphrodite

Question 32

What is the scolex?

Answer 32

Head rejoin, which has hooks and suckers that attach to the intestine wall

Question 33

What are the strobilia?

Answer 33

proglottids, which make up the rest of the tape worm, made of repeated segments, each containing a complete, sexually mature reproductive system

Question 34

Describe the lifecycle of a beef tapeworm

Answer 34

Eggs are injected by the intermediate host, cattle. The larvae migrate to the muscles, are then eaten by humans, the definitive host