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2nd Year: Animal Biodiversity > PLatyhelminthes > Flashcards

PLatyhelminthes Flashcards

1
Q

What are playhelminthes?

A

Flatworms.

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2
Q

Where are they found?

A

Terrestrially, freshwater, marine waters and ephemeral pools.

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3
Q

Which group are they classified within?

A

The lophotrochozoa.

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4
Q

List 5 synapomorphies of Platyhelminthes.

A
  1. Dorsoventrally flattened
  2. Mostly hermaphrodite (although can be dioecious)
  3. Acoelomate
  4. A blind gut (only a single opening, no anus)
  5. Possess an integument
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5
Q

Define an integument.

A

A tough, outer protective layer. Often ciliated in free-living species.

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6
Q

Excretion is via the protonephridia. What are they?

A

Similar to kidneys: a network of dead-end tubules with no internal openings. Tubules end in flame cells.

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7
Q

Platyhelminthes possess totipotent cells throughout their lifetime. True or false?

A

True: they have hugely regenerative properties.

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8
Q

Define a flatworm neoblast.

A

A somatic stem cell, have huge nuclei.

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9
Q

What is characteristic about cell division in Platyhelminthes?

A

Their stem cells are the only cells to divide. A stem cell will divide into a terminally differentiated cell and another stem cell. The stem cell will go onto divide and the other cell will not.

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10
Q

There are 2 major groups of Platyhelminthes that vary in lifestyle. What are they?

A
  1. Turbellarians

2. Neodermata

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11
Q

What are the turbellarians?

A

Free-living, however many enter endosymbiosis with other animals.

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12
Q

Why are turbellarians often used as regeneration models?

A

If you chop them into bits, as long as each part has at least one stem cells it can grow into a whole new organism.

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13
Q

What are the neodermata?

A

Obligate parasites, most species fall into this category.

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14
Q

Give some examples of neodermata.

A

Blood flukes, tapeworms, monogeneans.

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15
Q

What were the ancestral hosts for neodermata?

A

Fish, both chondrichthyans and osteichthyhans. Now it is all vertebrate species.

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16
Q

What are the 2 styles of parasitism?

A
  1. Active: organism seeks out a host

2. Passive: organism is accidentally consumed

17
Q

How do many flatworms evade the immune system of their host?

A

By secreting toxins or enzymes from their tegument.

18
Q

Parasites are often referred to as R-strategists. What does this mean?

A

They have massive reproductive outputs with no parental care.

19
Q

How many eggs can organisms generate per day?

A

~10,000s, they have huge uteruses.

20
Q

What are the 3 main species of neoderm?

A
  1. Trematoda: the flukes
  2. Cestoda: the tapeworms
  3. Monogenea: fish parasites
21
Q

What are the blood flukes called?

A

Digenea.

22
Q

Digenea is the most diverse flatworm group. How many species are there?

A

~18,000.

23
Q

Digenea need between 3-5 hosts. What is always the primary host?

A

A snail.

24
Q

Schistosoma mansoni is a human parasite. What is characteristic about reproduction in this species?

A

The female will not sexually mature until she is within proximity of a male. She then lives permanently in his gynaecophoric canal.

25
Q

What disease does schistosoma mansoni cause in humans?

A

Schistosomiasis.

26
Q

What disease does schistosoma mansoni cause in humans?

A

Schistosomiasis.

27
Q

Where does schistosoma mansoni live in humans?

A

In the blood vessels, although the eggs must be released into the gut for excretion to continue the lifecycle.

28
Q

In cestoda (tapeworms), what percentage of the body is made of reproductive segments?

A

95%: each segment contains both male and female organs.

29
Q

Cestodans have lost discrete skin cells. Their surface is effectively one giant cell. What advantage does this have?

A

Increases surface area for substance diffusion.

30
Q

Many cestodans have lost their digestive systems. Why?

A

They are mostly enteric (gut) parasites and absorb already digested nutrients through their surface.

31
Q

What is the primary host of a cestodan?

A

An arthropod.

32
Q

What kind of parasitism do tapeworms have, active or passive?

A

Passive.

33
Q

There are only ~4-5 species of cestodan that infect humans. When is infection most dangerous to us?

A

When we are the intermediate hosts.

34
Q

What is characteristic about monogeneans in contrast to digeneans/cestodans?

A

They are external parasites, whereas the other 2 are internal.

35
Q

Where do monogeneans attach to their fish hosts?

A

On the gills and skin.

36
Q

Diplozoon paradoxum is a monogenean with extreme phenotypic plasticity. How does it become an adult?

A

Hermaphrodite larvae fuse to form an adult - even the internal duct-work fuses within them.

2nd Year: Animal Biodiversity (16 decks)

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