AD lophotrochozoa

Question 1

What is the size range of Annelida?

Answer 1

0.5mm-4m

Question 2

Describe the general body plan of annelida

Answer 2

Segmented
Segments separated by septa
Hydrostatic skeleton (coelom filled with liquid)
Triploblastic
Closed circulatory system
Cephalisation of NS
Specialised gut region eg crop, stomach

Question 3

What is metamerism?

Answer 3

Helps in finding and feeding of food particles

Question 4

Describe metamerism and locomotion

Answer 4

Contraction of longitudinal musculature
Coelomic fluid puts pressure laterally
The body expands
Contraction of circular musculature
Coelomic fluid puts pressure antero-posterior
Body elongates

Question 5

Describe the locomotion of errantia

Answer 5

Has complete septate

There is additional movement of parapodia

Question 6

Describe the locomotion of earthworms

Answer 6

Completely septate

Longitudinal muscles relax, circular muscles contract, then longitudinal muscles contract and circular muscles relax

Question 7

Describe the locomotion of leeches

Answer 7

No septae
Leeches move by either an undulating swimming motion (eel-like) or by an ‘inch-worm’ like crawling motion using the anterior and posterior suckers.
At first, the posterior sucker is attached to the substratum.
This produces a wave of contraction to pass forwards along the circular muscles, whilst the longitudinal muscles are kept in a relaxed state
The animal now fixes its anterior sucker upon the subs­tratum. This produces contraction of the longitudinal muscles and simultaneous relaxation of the cir­cular muscles.

Question 8

How do annelids feed?

Answer 8

Small particles
Surface deposit feeders
Suspension feeders
Direct deposit feeders

Question 9

Describe how an earthworm feeds

Answer 9

Anecic: Litter and soil feeder
Endogeic: Rich soil feeder
Epigeic: Litter feeder

Question 10

Describe how a leech feeds

Answer 10

Bloodsuckers

Anticoagulants cause wounds to carry on bleeding

Question 11

Describe the general reproductive features of Polychaetes

Answer 11

Gonochoristic (sep sexes)
No permanent sex organs
Gametes develop in coelom

Question 12

Describe the asexual reproduction

Answer 12

Multiple fission
Adult splits into individual segments
Each segment grows a head and a tail by proliferation
Reproduction alternates between asexual and
sexual. Fragments that have reproduced sexually
then die

Question 13

What is the process of epitoky?

Answer 13

Entire animal or part of animal metamorphose into sexual mature form
E.g. Paloloworm and Syllids transform part of body into epitoke
Epitokes are released and spawn in co-ordinated swarms
Reproduction not terminal

Question 14

Metamorphosis is co-ordinated by what?

Answer 14

Environmental triggers eg temp

Question 15

Swarming is co-ordinated by what?

Answer 15

eg lunar phase

Question 16

Mate location and release of gametes co-ordinated by what?

Answer 16

Pheromones

Question 17

Describe reproduction in earthworms

Answer 17

Mainly hermaphrodites
Parthogenesis (asexual) in some species
Self-fertilisation in some species
Cross-fertilisation in some species
External fertilisation in the cocoon is the norm
No larval stage so direct development
Juvenile worm emerges from cocoon in the soil

Question 18

What is a trochophore?

Answer 18

Free swimming larva characteristic of many annelids and molluscs

Question 19

Describe reproduction in leeches

Answer 19

No asexual reproduction
Sexual reproduction – in some species it is very similar to that in oligochaetes
(both are clitellate and hermaphrodite).
• Some species have a penis
• Sometimes hypodermic impregnation
• Sperm packages (Spermathophora)
• Internal fertilization with most mating by implanting a “spermatophore”
(sperm package) into their partner
• Transfer of fertilised egg to cocoon
• Juvenile leech hatches from cocoon