Annelids

Question 1

Which protostome group are annelids in?

Answer 1

Lophotochozoans

Question 2

What does ‘annelid’ mean?

Answer 2

‘ringed worm’

Question 3

What are the features of an Annelid’s body?

in terms of segments

Answer 3

> Metamerically segmented
Segments added in front of pygidium
Some have set no. of segments

Question 4

What are the other features of Annelida bodies?

Answer 4

> Body wall w/ outer circular & inner longitudinal muscle layers
Transparent moist cuticle
Chitinous setae
- often present on parapodia

Question 5

What does the septum allow?

Answer 5

different muscle groups to do different things

Question 6

Is their circulatory system ventral or dorsal?

What about their nervous system?

Answer 6

Dorsal

Ventral

Question 7

How many germ layers do annelids have?

Do they have a coelom?

Answer 7

3
= triploblastic

Yes
= coelomate

Question 8

What functions as a hydrostatic skeleton?

And what is this used for?

Answer 8

Coelomic fluid

Supplies turgidity
- circular & longitudinal muscles can work against it

Question 9

What happens when the circular muscles contract?

What about the longitudinal muscles?

Answer 9

Long & thin

Short & fat

Question 10

Describe annelida blood systems

Answer 10

Closed
Segmentally arranged
Contains respiratory pigments e.g. Hb

Question 11

Describe annelida digestive systems

Answer 11

Complete

Not metamerically arranged

Question 12

Describe gas exchange in annelida

Answer 12

Through skin, gills or parapodia

- can be via cuticle & gut too

Question 13

Describe annelida’s excretory system

Answer 13

Pair of nephridia for each metamere

Question 14

Describe annelida nervous systems

Answer 14

Double ventral nerve chord & pair of ganglia w/ lateral nerves in each metamere

Question 15

Describe annelida brains

Answer 15

Pair of dorsal cerebral ganglia w/ connections to cord around oesophagus

Question 16

Describe annelida sensory systems

Answer 16

Tactile organs
Taste buds
Photoreceptor cells
Eyes w/ lenses

Question 17

How do annelids reproduce?

Answer 17

Hermaphroditic OR separate sexes

Asexual reproduction by budding in some

Question 18

What are the 3 main Annelid groups?

Answer 18

Polychaeta (e.g. ragworms)

Oligochaeta (e.g. earthworms)

Hirudinea (e.g. leaches)

Question 19

How are the 3 Annelid groups related?

Answer 19

Paraphyletic

Oligochaeta derived from Polychaeta

Hirudinea derived from Oligochaeta

Question 20

What is tagmosis?

Answer 20

Different segments of body carry out different functions

Question 21

Polychaeta means what?

Answer 21

‘many chetae’

Question 22

What are the features of Polychaeta?

Answer 22

> Well-differentiated head w/ specialised sense organs
Paired, paddle-like parapodia
Don’t have lophophores but do have trochophores
Separate sexes
- hatch into planktonic larva
- later metamorphose into juvenile annelid

Question 23

Give an example of a Polychaeta

Answer 23

Neresis

ragworm

Question 24

What are the 3 different Polychaete life habits?

Answer 24

> Errant = free moving 
e.g. Neresis & Aphrodite 
> Sedentary burrowers e.g. Arenicola
>Sedentary tube formers
- filter feeders e.g. Sabella, Serpulid
-nutrition from endosymbiotic bacteria 
e.g. Riftia pachyptila

Question 25

Why species example has iridescent chaetae?

Answer 25

Aphrodite aculeata

= a sea mouse

Question 26

Tube-living, deposit-feeding annelids ingest up to how much of their own body weight a day?

Answer 26

120x

Question 27

What features do tube-living, filter-feeding annelids have?

Answer 27

> Tentacles w/ respiratory & feeding functions
Light sensors on tentacles detected shadows - pulls tentacles into tube when threatened
Food particles passed via mucus band to back of mouth

Question 28

What are deep sea hydrothermal vents rich in?

Answer 28

Reduced chemicals e.g. sulphides & methane

Question 29

Riftia pachyptila has no gut. How does it gain nutrition?

Answer 29

Depends on chemoautotrophic symbiotic bacteria - pack a large organ called trophosome

• -> Hb in gill-like plumes captures H2S from vent + CO2 from water
• -> generates organic carbon using sulphide as e donor & O2 as e acceptor

Question 30

Give an example of an Oligochaeta

Answer 30

Lumbricus

=Earthworms

Question 31

What are the key features of Oligochaeta?

Answer 31

> most bear setae
hermaphrodites
clitellum for brooding eggs
predators, detritivores & direct deposit feeders

Question 32

How do earthworms move?

Answer 32

1. contrat circular muscle
2. contract longitudinal muscle
3. front end bulges out
4. push setae out

Question 33

What are the key features of Hirudinea?

Answer 33

> fixed no. of segments - approx 34
> anterior & posterior suckers
> coelom doesn't act as hydrostatic skeleton
> no septae or setae
> lack parapodia & tentacles

Question 34

Why doesn’t the coelom in Hirudinea act as a hydrostatic skeleton?

Answer 34

Packed with mesenchyme

Question 35

What are the medicinal uses of leeches?

Answer 35

> clear up discolouration of black eyes
> saliva contains anti-inflammatories
- relieve arthritis 
> used after surgery when reattaching skin flaps
- re-establish blood flow

Question 36

Describe digestion in leeches

Answer 36

> only exopeptidase
> slow digestion
> no food for <18months
> Aeromonas veronii = gut bacteria may contribute to digestion &amp; produce Vit B
> Blood in gut doesn't coagulate

Question 37

Which leech is used in medicine?

Answer 37

Hirudo medicinalis

Question 38

How do leeches prevent blood clotting?

Answer 38

Calin inhibits platelet adhesion to vessel wall
Decorsin inhibits platelet aggregation

Hirudin inhibits activation of prothrombin

Question 39

What 3 things does leech salvia contain?

Answer 39

Vosodilator
- dilates blood vessels

Anaesthetic
- reduces chance host feels leech

Antibiotic
- produced by symbiont Aeromonas