Clitella

Question 1

Clitella shared features

Answer 1

Terrestrial, FW and marine
No parapodia - rely on gaseous exchange on body surface, can produce mucous to occur there
Produce a clitellum (helps to produce cocoon)
Cocoon where egg develops (very yolky) - no larval stage
Hermaphrodites
Gonads in few segments

Question 2

Oligochaetes

Answer 2

Few setae
Well developed septa (with few) used in peristalsis and burrowing
Alter behaviour dependent on dampness of soil (burrow deep if dry etc.)
Darwin interested in them - to see preferences, food and light
Also to see if showed intelligence - filled burrows with vegetation to minimise drag every time

Question 3

Ecotypes of oligochaete

Answer 3

Earthworm ecotypes…
Live on surface, or burrow in sand, form galleries where they live
Horizontal or vertical
Feed in soil or drag food into soil
Important in nutrient cycling, digest organic material and make available to others

Question 4

Oligochaete reproduction

Answer 4

Have male and female gonopore, spermathecal opening and sperm grooves
Mutual sperm exchange
1. Pair head to tail
2. Bound together by substances in clitellum
3. Sperm released from male G to sperm grooves and to spermathecal opening of opposite worm
4. Worms come apart and clitellum produces mucous and cocoon
5. Worm wriggles through cocoon, passes female G where eggs are shed inside
6. Wriggles to spermathecal opening sheds other worms sperm inside
7. Cocoon passes head and seals up where offspring develop

Question 5

Hirudinean features

Answer 5

Most advanced
No settee
Restricted segments - only have 34 (appears as more)
Anterior and posterior suckers (on 1st and last segments)
No clear division of septa
Mutual sperm transfer, can be aggressive hypodermic insemination
Crawl with suckers - well developed longitudinal muscles
-some swim by undulating bodies

Question 6

Hirudinean feeding

Answer 6

Predacious - other small inverts
Proboscis used for sucking on others
Or have structures used to slit the skin of others open to feed
Blood suckers - can produce anticoagulant - hirudin, a potential anaesthetic but not sure
Take up 10x body weight in blood, absorb water and have symbiotic bacteria that break this down - taking up to 6 months