Lophotochozoa I – Annelids

Question 1

Describe the Annelids

Answer 1

• highly ecologically important and taxonomically narrow phylum
• 12,000 species
• segmentation using septa

Question 2

Define segmentation

Answer 2

• coincident repetition of characters
• muscles, nervous system, excretory system and coelom
• exclusion: prostomium which is unsegmented

Question 3

Describe the features of Annelids

Answer 3

• vermiform
• large coelom
• compounded by a hydrostatic skeleton of fluid filled spaces
• movement of the circular and longitudinal muscles, and the ventral nerve cord
• water-permeable skin

Question 4

vermiform

Answer 4

• lengths are much greater than their widths
• soft-bodied

Question 5

What is the importance of the epithelial cells?

Answer 5

key to animal organisation

Question 6

Describe water-permeable skin

Answer 6

• ecologically constrains to aquatic semi-terrestrial wet environments
• facilitate gas exchange to a greater degree

Question 7

Describe the taxonomic classification of Annelida

Answer 7

3 classes
- the Polychaeta
- the Oligochaeta

Question 8

Polychaeta

Answer 8

• ragworms
• lugworms
• fanworms

Question 9

Oligochaeta

Answer 9

e.g. earthworms

Question 10

Hirudinea

Answer 10

e.g. leeches

Question 11

Clitellata

Answer 11

• Oligochaeta
• Hirudina
• paraphyletic

Question 12

Polychaetes can be ecologically classified into:

Answer 12

• errant
• sedentary
• generally marine

Question 13

Describe errant polychaetes

Answer 13

• eyes and sensory appendages
• use their segments in undulations to crawl or swim
• active predators that bite.

Question 14

Describe Polychaeta locomotion

Answer 14

• contraction and relaxation of the longitudinal muscles
• extension and contraction of the parapodia for added power

Question 15

Describe sedentary polychaetes

Answer 15

• live in burrows and tubes
• crown
• mouths fanned by radioles, which lead down into the ventral sac and tube
• water flows in antiparallel

Question 16

Describe the sedentary polychaete ventral sac

Answer 16

• sand storage
• latterly used for tube building

Question 17

Describe the sedentary polychaete tube

Answer 17

for consumption

Question 18

Describe sedentary polychaete radioles

Answer 18

• size-discriminating sorting mechanism: large particles are discarded, smaller particles are consumed
• use food grooves with pinnule extensors that are covered in cilia, creating a ciliary tract to direct food movement for consumption
• ciliary feeding

Question 19

Describe sedentary polychaete use of segments

Answer 19

• peristalsis
• contacting the circular and relaxing the longitudinal muscles to thin segments and vice versa

Question 20

Segments and parapodia can be used for

Answer 20

• tube irrigation
• to ensure aquatic freshness

Question 21

Describe polychaete reproduction

Answer 21

• dioecious
• gametes released into the marine environment for external fertilisation, where the larval stages of the life history will also occur

Question 22

Dioecious

Answer 22

not hermaphroditic

Question 23

Describe the Oligochaetes

Answer 23

• use their segments for peristalsis and locomotion
• freshwater or semi-terrestrial, soil-based environment
• no parapodia, eyes or head tentacles
• hermaphroditic mating system
• e.g. earthworms

Question 24

Describe Oligochaete mating

Answer 24

• secretory clitellum structure
• three specialised gametogenetic segments
• any two oligochaetes can mate

Question 25

What are three specialised gametogenetic segments of oligochaetes?

Answer 25

- the sperm store (spermatheca) - the female gonad - male gonad.

Question 26

Describe Oligochaete mating post-separation

Answer 26

clitellum secretes mucous cocoon that picks up the self-eggs, and the sperm from the spermatheca, to achieve fertilisation.

Question 27

Describe the Hirudinea

Answer 27

- predators - blood-sucking ectoparasites - hermaphroditic e.g. leeches

Question 28

Describe Hirudinea morphology

Answer 28

- similar to Oligochaetes - secondary loss of septa for stretching capacity: increased volume for consumption of a blood meal, but constrained locomotion

Question 29

Describe Hirudinea locomotion

Answer 29

looping and suckers

Question 30

Describe Hirudinea in therapy

Answer 30

- help with post-operative venous congestion and swelling of digits and extremities - due to the surgical inability to sew the small vein network

Question 31

Describe the Sipuncula

Answer 31

- marine - burrowing - lost their segmentation - aka peanut worms

Question 32

Describe the Echiura

Answer 32

- flattened, grooved proboscis that projects over its environmental sediment - body exists in a burrow - aka spoon worms

Question 33

Bonellia viridis

Answer 33

- species of Echiura - extraordinary sex dimorphism: females generally 10-100cm, males, exist endoparasitically to the female and are 1-3mm