Annelida

1
Annelida

• Chapter 13

2
Annelida

• Characteristics
• Metamerism - Segmented body
• Bilateral
• Wormlike
• Epidermal Setae
• Closed Circulatory System
• Dorsal ganglia and ventral nerve cord
• Metanphridia or protonephridia

3
Annelida

• Metamerism and Tagmatization
• Metamerism segmentation of the body
• While the external segmentation is obvious, the
  internal structures are also segmented

4
Annelida

• Advantages of being compartmentalized
• Flexibility
• Locomotion
• Coelomic space
• Coelomic muscles
• Tagmatization the specialization of body
  cavities for various functions

5
Annelida - Class Polychaeta

• Class Polychaeta
• Characteristics
• Marine
• 5 10 cm in length
• 5,300 species
• Largest of the annelid classes

6
Annelida - Class Polychaeta

• External Structure and Locomotion
• Parapodia lateral extensions supported by
  chitin
• Setae bristles secreted from the distal ends of
  the paraprodia

7
Annelida - Class Polychaeta

• Locomotion
• Slow Movement - 6-8 segments for each wavelength
• Fast Movement - 14 segments for each wavelength
• Swimming 40 segments for each wavelengths

8
Annelida - Class Polychaeta

• Prostomium
• Lobe that contains nuchal organs
• Located anterior and dorsal to the mouth
• Nuchal organs - eyes, antennae, palps, and
  ciliated grooves

9
Annelida - Class Polychaeta

• Peristomium - first body segment surrounds the
  mouth
• Annelids also secrete a nonliving cuticle from
  the epidermis for protection

10
Annelida - Class Polychaeta

• Digestive System
• Parts - pharynx, crop, gizzard, and intestine
• Predators, filter feeders, and herbivores
• Some Polychaetes can absorb between 20 -40 of
  the food.
• Waste removal can be a problem for tube dwelling
  polychaetes

11
Annelida - Class Polychaeta

• Gas Exchange
• Oxygen diffuses through the body wall.
• Circulatory system is closed
• Oxygen is carried by molecules called respiratory
  pigments
• This in turn makes the blood colorless, green, or
  red.

12
Annelida - Class Polychaeta

• Nervous and Sensory Functions
• A double ventral nerve cord runs the length of
  the worm
• A paired segmental ganglion is present in each
  segment
• The function of the nervous system is to
  coordinate swimming and crawling

13
Annelida - Class Polychaeta

• Sensory Stuctures
• 2 to 4 eyes
• Chemoreceptors

14
Annelida - Class Polychaeta

• Excretion
• Annelids excrete ammonia
• Nitrogen diffuses across the body wall
• Most of the excretory organs in annelids are
  active in regulating water and ion balances
• Nephridia excretory organs in annelids
• Two types

15
(No Transcript)
16
Annelida - Class Polychaeta

• Regeneration
• Replace lost parts
• Sexual reproduction is most common form of
  reproduction
• Most are dioecious
• Fertilization is external in most
• Internal fertilization
• Male inserts his anus into the females mouth

17
Annelida - Class Clitellata

• Subclass Oligochaeta - earthworm or night
  crawlers

18
Annelida - Class Clitellata Subclass Oligochaeta

• Characteristics
• 3000 species
• freshwater and terrestrial habitats
• In hot weather they may burrow up to 3 meters
  below
• Condition the soil help to remove organic
  components and turn the soil

19
Annelida - Class Clitellata Subclass Oligochaeta

• External Structure and Locomotion
• Fewer setae than polychaetes
• No parapodia (lateral extensions)

20
Annelida - Class Clitellata Subclass Oligochaeta

• Clitellum - swollen area that secretes mucous to
  aid in copulation and makes a cocoon
• Locomotion is performed by the antagonism of
  circular and longitudinal muscles

21
Annelida - Class Clitellata Subclass Oligochaeta

• Feeding and Digestive System
• Nutrition is usually fallen or decaying plants
• Crop - thin-walled storage structure
• Gizzard - muscular, cuticle lined grinding
  structure
• Calciferous glands - rid the body of excess
  calcium and regulate pH
• Gas Exchange
• same as polychaetes - diffusion

22
Annelida - Class Clitellata Subclass Oligochaeta

• Nervous System
• Escape response can be initiated at either end of
  the organism
• Epidermal light sensory
• Postive phototaxis in weak light - movement
  toward darkness
• Negative Phototaxis in strong light - movement
  away from light
• Epidermal chemoreceptors

23
Annelida - Class Clitellata Subclass Oligochaeta

• Excretion
• Use metanephridia
• Retain ions from water
• Excretes amonia and urea
• Chloragogen tissue
• liver like tissue (amino acid metabolism)
• Converts amonia to urea
• Converts carbs to glycogen and fat

24
Annelida - Class Clitellata Subclass Oligochaeta

• Reproduction
• All are monoecious
• Clitellum secretes mucous to maintain contact
• Both worms transfer sperm
• Copulation can last two to three hours
• Cocoon forms from the clittelum
• Fertilzation takes place in the cocoon

25
Annelida - Class Clitellata Subclass Hirudinea

• Subclass Hirudinea -Leeches
• Characteristics
• 500 species
• most are freshwater
• Prey on small invertebrates or on the body fluids
  of vertebrates

26
Annelida - Class Clitellata Subclass Hirudinea

• External Structure and Locomotion
• Annuli are subdivided segments
• One main coelomic cavity
• Setae are absent
• 34 segments

27
Annelida - Class Clitellata Subclass Hirudinea

• Feeding and Digestive System
• Predators not parasites
• Class specific
• Gas Exchange
• across the body wall

28
Annelida - Class Clitellata Subclass Hirudinea

• Nervous System
• Temperature senses
• Excretion
• 10 to 17 nephridia
• Reproduction
• Monoecious
• Reproduce sexually
• Clitellum present only in the spring

29
(No Transcript)