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Flashcards in Lecture 3 RH Deck (79)
1

What are the 3 phyla of worms?

Platyhelminthes

Nematodes

Annelids

2

Are worms coelomates?

Different phyla have different properties when it comes to the body cavity:

Platyhelminthes are acoelomate

Nematodes are blastocoelomates

Annelids are normal coelomates

3

How are the coelomes of the different phyla of worms different?

Coelomates have mesoderm derived tissue lining the coelom all around the body cavity and the organs.

Blastocoelomates coeloms are lined by mesoderm tissue only on the outside of the cavity.

4

What is a feature that is common to all worm phyla regarding their embryonic development?

All worms develop from 3 embryonic layers and are tripoblastic.

5

What do platyhelminthes look like?

They are flat and long.

Many are parasitic.

6

What are the key features of platyhelminthes?

Triploblastic

Acoelomate

Bilaterally symmetrical

Blind gut or not gut

Unsegmented

Flat

Cellular filling between epidermis and gastrodermis is the parenchyma

Muscles: Longitudinal, circular, dorso-ventral, oblique

No circulatory or gas exchange system

Excretory system: Protonephrida

Hermaphroditic

7

What is the cellular filling in platyhelminthes between the epidermis and the gastrodermis called?

Parenchyma

8

What is the musculature of platyhelminthes like?

They contain longitudinal muscles that form a ring around the animal and run all the way anteroposteriorly

Circular muscles form a ring around the body cavity

Parenchymal muscles run dorsoventrally

9

Are platyhelminthes ciliated?

Yes, they use it to glide across a surface

10

Why can platyhelminthes grow to such massive lengths?

Their flat body structure creates a high surface area which allows more easy gas exchange and nutrient exchange with environment.

11

How do platyheminthes regulate osmolarity?

They use protonephridia

12

How do platyhelminthes osmoregulate?

Tubules run from parenchyma to pores on outside of the body used and if you expand one of those you would see excretory duct/nephridiapore. the rest of the tubule is buried in the parenchyma and contains flame cells at the end of it to draw water through it and down through the tubule. This structure contains cilia which allows liquid movement.

Some of this fluid can be reabsorbed by the worm in the excretory duct to form more concentrated excretion.

13

What are the classes of platyhelminthes?

Turbellaria

Monogenea

Trematoda

Cetoda

14

What kind of grouping is class turbellaria?

Paraphyletic grouping

15

What are the key features of class turbellaria?

They are not parasitic

Very diverse and capable of living in many habitats (marine, freshwater, and terrestrial)

Well developed brain with ganglia

Cephalised (complex nervous system and sensory organs such as statocysts, ocelli, chemo and mechanoreceptors)

16

What are the kinds of sensory receptors that turbellaria contain?

Statocysts (balance receptors)

Ocelli (simple photoreceptors)

Chemoreceptors

Mechanoreceptors

17

What does the gut of the platyhelminth look like?

Very branched with a pharynx that leads to it posteriorly.

18

What are the methods of locomotion of turbellarians?

Ciliary gliding (use mucous and cilia to glide)

Pedal waves (moves side of body in waves which moves it forwards)

Looping by moving the entire body from heel to head and "roll" with temporary attachments.

19

How do turbellarians temporarily attach to the substratum?

Using suckers

Using mucus and adhesive cilia

Using Duo gland adhesive system.

20

How does the duo-gland adhesive system work in platyhelminthes?

Viscid glands release sticky mucus and releasing gland liquefies the mucus to release.

21

What is the function of turbellarian rhabdites?

Capsules released into epidermis from parenchyma and they absorb water and expand and create mucus.

These cells are also important for defending the cells and recognizing chemical threats.

22

How do turbellarians reproduce?

They are hermaphrodites. The stylet penis pierces mate's body wall and injects sperm.

23

What larva is formed in turbellarians?

Muller's larva

24

What are the common adaptations of the parasitic classes of platyhelminthes?

Uncephalized, reduced nervous system, fewer sensory organs

Loss of feeding structures or gut

Loss of ventral locomotory cillia

Attachment organs or hooked mouthparts

Sucking mouthparts

Syncytial tegument

Avoidance of host immune system

Facultative anaerobes

Hermaphroditism

Complex life cycles (including asexual preproductive stages)

High rate of reproduction

Multiple hosts

Motile or encysted stages that transfer to new host

Alter behavior of host to promote successful transmission

25

What is the syncytial tegument?

Replaces ciliated epidermis and this is a joining of cells within the parenchyma to the outer zone of the neodermis in a way that the cytoplasm of these cells is continuous with this zone.

As a result this layer is multinucleated and as a result has immune evading capabilities.

26

What are the parasitic classes of platyhelminthes?

Monogenea (ectoparasites)

Trematoda (endoparasites/flukes)

Cestoda (endoparasites, tapeworms)

27

What types of hooks are characteristic of class monogenea?

Opisthaptor

28

What defines monogenea?

Platyhelminthes that live on a single host and are ectoparasites

29

What are the components of the anterior mouth of the trematodes?

Oral sucker at one end and a muscular pharynx at another

30

What are the hosts that liver flukes have?

Snail

fish

Human

31

What is the life cycle of the liver fluke?

1) Adults undergo Sexual reproduction releasing fertilized eggs in human faecies

2) Egg contains miracidium which hatches after being eaten by a snail or burrow into snail's body

3) Miracidium undergo asexual reproduction in the snail creating sporocysts and redia in massive numbers.

4) Redia form Cercaria which swim through the water habitat to enter fish.

5) Humans eat fish reintroducing more liver flukes into the new life cycle.

32

What is a miracidium?

larval stage of the liver fluke

33

What do redia do?

They form cercaria which can infect fish

34

What does the liver fluke do to people with celiac's disease?

It reduces the symptoms

35

What are the features of tapeworms?

No digestive system and other body organs. Instead they directly absorb nutrients via their cell membranes

36

What are proglottids?

Proglottids are segments of cetodes (tapeworms). Each segment contains a separate reproductive system.

37

What is the lifecycle of beef tapeworm like?

Human feces contains proglottid -> grass contains larva (oncosphere) -> Grass ingested by cow -> Cysts form in muscle of cows -> human eats rare beef getting tapeworm

38

Are tapeworms specific with their host?

No

39

What are potential complications of tapeworms?

They can form a hydated cysts which can travel in the systemic circulation and has tumour-like symptoms

40

What are the features of nematodes?

Thread-like appearance

more than 25000 species in every form of habitat

Most are microscopic but parasites can often get to macroscopic sizes

Extremely abundant in their habitats

Blastocoelomates

Triploblastic

Bilaterally symmetrical

Protostome

Complete gut

Unsegmented

41

What is the difference between a blastocoelom and a normal coelom?

Blastocoelom contains mesodermally derived tissue around the cavity (like parietal peritoneum and no visceral peritoneum)

Coelom contains mesodermally derived tissue around organs and the full cavity

42

What makes up the nematode anatomy?

Collagen cuticle with crossed fibers preventing deformation.

Cuticle is molted 4 times during lifetime.

Longitudinal muscles in 4 bands, but no circular muscles; no peristalsis just writhing motion

Some species have syncytial epidermis

No locomotor or feeding cilia

Brain, dorsal, and ventral nerve cords

Chemosensory organs: Amphids anterior, phasmids posterior

No circulatory or gas exchange system.

Excretion by renette cells

Dioecious, internal fertilization; free-living worms have no larvae, parasites variable.

Eutly: constant number in adults

43

What are amphids?

anterior chemosensory organs in nematodes

44

What are phasmids?

Posterior chemosensory organs in nematodes

45

What are renette cells?

Excretory cells in nematodes

46

What are the characteristics of nematode reproduction?

They are dioecious, fertilization happens internally.

47

Do nematodes produce larvae?

Free-living don't produce larvae

Parasitic nematodes are variable

48

What are defining characteristics of nematodes?

Their chemosensory organs

49

What does Eutely mean?

Cell division stops at maturity and so there is a constant cell number in adults

50

What is the hookworm life cycle like?

Embryos exit in human feces -> larvae emerge in soil -> larvae penetrate circulatory system through feet -> carried into heart then lungs -> migrate from lungs to pharynx and is swallowed -> goes through GIT to intestines

51

What do filarial nematodes do?

Block organs or circulatory system

Intermediate host is blood sucking insect (eg mosquito)

*examples of these worms include heartworm and elephantiasis

52

What are the key features of phylum annelida?

Segmented

Coelomate

Protostome

Triploblastic

Complete gut

Chitinous setae in epidermis used for traction

Have a brain, ventral nerve cord, and metameric ganglia

Closed circulatory system

Metanephridia for excretion

53

What are the annelid classes?

Polychaeta

Oligochaeta

hirudinea

*these are old classifications that are currently under review

54

What are the advantages of having a coelom?

Can act as a hydrostatic skeleton

Cushioning for the digestive tract

Muscular movements of digestive tract isolated from outer body wall and skeletal muscular movements

Coelom can function in circulation, waste removal, gamete storage, and gamete release

55

What is metameric segmentation?

Body is divided into segments with serially repeating organ systems.

Serial homology; homologous segments arranged in linear order

56

What is serial homology?

All segments arised from the same body plan and developmental origin

57

What are the advantages of metameric segmentation?

Improved locomotion efficiency using hydrostatic skeleton

Independent nervous control and movement of segments

Architectural redundancy allows specialisation of segments as well as survival/regeneration when segments are lost.

58

How does peristaltic motion work?

1) Circular muscles contract creating longer and thinner segments

2) Forward segments form an anchor when longitudinal muscles contract and fatten them.

3) The longitudinal muscles bring the entire body of the worm forwards

59

How does the metanephridium?

Opens on one end to the segment before it and opens on the other end to the outside via nephridiopore

60

What are the features of the polychaete class?

Mostly marine

Paradopia (contain fleshy lobes that are not jointed)

Numerous setae

Diverse anterior appendages

Some appendages can function as gills, or gas exchange across parapodia.

Diverse locomotion, feeding modes, ecological niches.

Trochopore larvae

61

What are parapodia?

Fleshy lobes found in polychaetae. Setae protrude from these parapodia.

These increase surface area significantly

62

What is a trochophore larva?

The larvae of annelids with bands of cilia around them.

They have a complete gut but no coelom

63

What is the cycle that benthic aquatic invertebrates usually follow during their life?

Most benthic aquatic invertebrates have a planktonic larval stage that disperses.

Adult stage associated with substratum

Larvae respond to various cues from physical and biological environment when selecting settlement site

64

How do larvae choose where they settle on the substratum?

Cues are used by larvae to know whether they want to settle down on a surface or not. Some larvae react positively while others react negatively

65

How do polychaete feed?

Suspension feeding: Capture food from water via tentacles which contain cilia.

Deposit feeding: Feed on material that falls to the bottom of the water using their tentacles.

66

Are polychaete's mobile?

Some are, some are not

67

What can the eversible pharynx be used for and how?

Scavenging

Predation

Deposit feeding

68

What is the function of the eversible pharynx?

picks up particles from around by extending the pharynx

69

How do modified parapodia assist in filter feeding?

Water moves through a hollow tube which leads to the mouth and food gets caught in a mucous net and is directed to a food cup.

70

What are the features of siboglonid polychaetes?

No mouth, gut, or anus

Digest symbiotic chemosynthetic bacteria that grow in specialised organ (triphostome), deriving energy from reduced chemicals in the environment.

71

What are the features of class oligochaeta?

Mostly terrestrial or fresh water burrowers

No parapodia, few setae, reduced head appendages

Hermaphroditic

Clitellum secretes mucous cocoon for eggs and sperm

Direct development (no larval stage)

72

How do earthworms reproduce?

1) 2 worms come next to each other and fill up with sperm from each other at the sperm receptacle.

2) Eggs deposit in mucous sac

3) Fertilization

4) Cocoon slips off and forms another individual (no larval stage)

73

Which classes share the clitellum? What is the clittelum?

Clitellum is an important organ for fertilization to take place and to eventually form a cocoon.

Oligochaeta and hirudinea share the clitellum.

74

What are the features of hirudinea?

Mostly freshwater predators or ectoparasites

No paradopia, setae, or internal septa

Fixed number of segments (usually 34), external secondary annulation

3 jaws with teeth

Parasites have anterior and posterior suckers

Clitellum evident only during breeding season

Mostly direct development

75

What is external secondary annulation?

False rings externally

76

What do leeches inject when biting?

Anticoagulant (hirudin)

Vasodilator

Anaesthetic

77

What does the muscular pharynx do in leeches?

Pumps blood

78

How are hirudo medicinalis (leech) teeth arranged?

3 Y-shaped blade-like jaws make efficient cut that takes long time to heal

79

What is the problem with current class classification of Polychaetes and oligochaetes?

They are paraphyletic and undergoing changes