2. At the time of the November full moon on
islands near Samoa in the South Pacific,
people rush about preparing for one of
their biggest yearly feast. In just one
week, the sea will yield a harvest that
can be scooped up in nets and buckets.
Worms by the millions transform the
ocean into what one writer called
“vermicelli soup!” Celebrants gorge
themselves on worms that have been
cooked or wrapped in breadfruit leaves.
3. Samoan Palolo worm
Stock photo of hunters with powerful lights used to attract more palolo worm, Palola
siciliensis, American Samoa, Pacific
4. Samoan Palolo worm
Image of palolo worms, Palola siciliensi, in water column after emerging from their
burrows on night of the spawning, Tutuila Island, American Samoa, Pacific Ocean
5.
6. Phylum Annelida
• Class Polychaeta
• Marine worms
• Class Clitellata
–Subclass Oligochaeta• Soiling building worms
–Subclass Hirudinea• Predatory leeches
7. Phylum Annelida
Characteristics
– Metamerism - segmented body
– Bilateral
– Protostome
– Wormlike
– Epidermal Setae
– Closed Circulatory System
– Dorsal ganglia and ventral nerve
cord
– Metanephridia or protonephridia
9. Advantages of Metamerism:
• 1. Hydrostatic compartmentsallows variety of locomotor and
supportive functions like
swimming, crawling, and
burrowing.
10. Advantages of Metamerism:
• 2. Lessens the impact of injuryif few segments injured others
can perform normal functions
which increases the likelihood
that the worm will survive.
11. Advantages of Metamerism:
• 3. Tagmatization- The specialization of
body regions in a metameric animal
• permits the modification of
certain regions of the body for
specialized functions like
feeding, locomotion, and
reproduction.
16. Class Polychaeta
Live:
• On the ocean floor
• Under rocks and
shells
• Within crevices of
coral reefs
• Some can burrow
17. External Structure and
Locomotion
Parapodia – lateral extensions
supported by chitin
Setae – bristles secreted from the
distal ends of the parapodia
• Important for locomotion/ digging
21. External Structure and
Locomotion
Prostomium- lobe that projects
dorsally and anterior to mouth
contains: eyes, antennae,
palps and nuchal organs
Nuchal organs: ciliated
sensory pits which are
chemoreceptors for food
detection
24. Prostomium and Peristomium
The prostomium (right) has
two antennae and two large,
two-segmented palps. The
peristomium (segment
behind the prostomium) has
4 pairs of tentacular cirri.
This photo is a 3d composite
made from a series of
photos using a Keyence
digital microscope. Photo by
Dave Cowles, July 2009
25.
26. Feeding and the Digestive System
Digestive tract is a straight tube:
Pharynx- when everted can form
a proboscis (See it)
Crop- storage sac
Gizzard- grinding
Intestine-long and
straight
27. Feeding and the Digestive System
• Polychaeta can be:
–Predatory-usually burrow or
live in coral crevices; some can
have poison glands
–Herbivores
–Scavangers
–Filter feeders- tube dwelling
(see them feed)
28. Examples of different worms and how they feed
Selective deposit feeders with tentacles.
Filter feeders with radioles.
29. Feeding and the Digestive System
Elimination of waste for
tube dwellers:
If open ends: wastes carried
away by water circulating in
tube.
If closed end: then the worms
either turns around in tube OR
uses ciliary tracts along body
wall to carry feces out.
30. Feeding and the Digestive System
• Polychaetes that inhabit
substrates rich in dissolved
organic molecules can absorb as
much as 20% to 40% of their
food across their body walls
(very unusual among animals)
31.
32. Gas Exchange and Circulation
• Respiratory gases diffuse across body wall
and parapodia (increase surface area)
• Closed circulatory system
• Oxygen is carried by molecules called
respiratory pigments- blood colorless,
green or red
33. Gas Exchange and Circulation
• Dosal aorta- propels blood from rear
(posterior) to front
• Ventral aorta- propels blood from
front to rear
• With Capillaries between the two aortas
34. Nervous and Sensory
• A pair of
Suprapharyngeal ganglia-
controls motor and sensory functions; feeding and
forward movement.
Connects to
• A pair of
Subpharyngeal ganglia-
mediates locomotor functions required for
coordination of distant segments.
By
• Circumpharyngeal connectives-run
dorsoventrally along the pharynx
35. Nervous and Sensory
• Ventral nerve cord
with paired
segmental ganglia in each segment; allows
escape response of segments
• Segmental ganglia- coordinate
swimming and crawling movements in isolated
segments.
• 2–4 pairs of eyes
37. Excretion
• Excrete ammonia
• Most of the excretory organs in
annelids are active in regulating
water and ion balances
• Nephridia – excretory organs in
annelids
38. Two types of Nephridia
• Protonephridia- tubule with a closed
bulb at one end and a connection to the
outside of the body at the other end.
• Metanephridia- open ciliated funnel
(nephrostome) that projects through
an anterior septum into the coelom of
an adjacent segment
42. Reproduction and Regeneration
•All polychaetes can regenerate
lost segments
•May have natural break points if
grabbed by predators (process
called autotomy)
•Some reproduce by fission or
budding
43. Reproduction and Regeneration
• Most sexually reproduce
• Most are dioecious
• External fertilization and
trochophore larvae
• Swarming occurs in some
species, where large numbers of
individuals join together to
release sperm and/or eggs
44. Reproduction and Regeneration
• Very few species copulate (most
external fertilization)
• A unique, weird, kinky copulatory
habit has been reported in
Platynereis megalops from Woods
Hole, Massachusetts. Read page
216 for the details. . .
45. Reproduction and Regeneration
• Epitoky-
formation of a reproductive
individual (an epitoke) that differs from
the nonreproductive form of the
species (an atoke).
• Epitoke- body modified into 2 body
regions; anterior segments-normal
maintenance; posterior segmentsenlarged & filled with gametes
• Example: Samoan palolo worm swarm
46. In some species the epitoke
breaks free from the atoke, which
stays in the burrow
The common clam worm
Nereis succineain its atoke
form (above) and epitoke
form (below). Especially
note the enlarged
parapodia on the epitoke; it
uses these to swim and
release eggs or sperm.
47. In others, the epitoke is
formed as part of the body,
and the whole animal leaves to
mate
Epitoke on the left,
atoke on the right
48. 3 Advantages of Swarming
Epitokes
1. Nonreproductive individuals
remain safe below the surface
waters; predators cannot
devastate an entire population.
49. 3 Advantages of Swarming
Epitokes
2. External fertilization requires
individuals to be ready at the
same time. Swarming ensures
large numbers of individuals are
in the right place at the right
time.
50. 3 Advantages of Swarming
Epitokes
3. Swarming of vast numbers of
individuals for brief periods provide a
banquet for predators. But because it
is such a BREIF period, predators can
only eat so much with respect to the
limits of their normal diets. Predators
can dine gluttonously and still leave
epitokes that will yield the next
generation of animals.
51. Class Clitellata
Earthworms and Leeches
Giant Blue Earthworm
Terriswalkeris terraereginae
mucin it releases is luminescent
Lives in rainforest in Australia
52. Class Clitellata
Earthworms and Leeches
•Have a clitellum
used in cocoon formation
•All are monoecious
•Have few or no setae
54. Subclass Oligochaeta
• 3,000 species
• Freshwater and terrestrial
habitats throughout the world
(some marine)
• Aquatic species live in shallow
water; burrow in mud and
debris
• Terrestrial species live in
soils with high organic content
55. Subclass Oligochaeta
So you want to see the
biggest earthworm in the
world? Go to Australia or
sit back and watch this. . .
Giant Gippsland Earthworm
56. External Features
• Have setae but fewer
• Lack parapodia- get in the way
because of burrowing
• Prostomium- lacks sensory
appendages
59. Locomotion
• Have both circular and longitudinal
muscles
• Move by antagonistic contractions of
these muscles
• Bulging and elongating body segments in
waves cause the worm to move forward
• Small setae help anchor the worm
• Small conical prostomium acts like a
wedge while burrowing, and soil is
swallowed (important for decomposition)
60. Feeding and Digestive System
• Scavengers-fallen and decaying
vegetation
• Mouth->muscular pharynx->esophagus
• Esophagus expanded form of stomach,
crop ( thin-walled storage structure),
gizzard (muscular grinding structure).
• Calciferous glands-evaginations of
esophagus wall that rids the body of
excess calcium absorbed by food;
regulates pH
61. Feeding and Digestive System
• Intestine-principle site of
digestion and absorption
• Anus
62. Subclass Oligochaeta
• Gas Exchange and Circulation:
same as polychaetes
• Nervous and Sensory: same as
polychaetes but lack welldeveloped eyes
63. Excretion
• Oligochaetes use metanephridia for
excretion of ammonia and urea and for
ion and water regulation.
• Chloragogen tissue- acts like a liver for
amino acid metabolism (deaminates
amino acids into ammonia and urea);
excess carbohydrates converts into
glycogen and water
64. Reproduction
•Monoecious
•Reproduce sexually via reciprocal
fertilization-both worms exchange sperm
(can last 2-3 hours!)
•Cocoon of mucous and chitinous materials
produced by clitellum
•Eggs, sperm, and food (albumen) deposited
in cocoon where fertilization takes place
•Young worms hatch from cocoon (no
larvae)
68. Subclass Hirudinea
• 500 species
• Mostly freshwater but some marine and
terrestrial
• Prey on small invertebrates or feed on
the body fluids of vertebrates.
69. External Structures
• Lack parapodia and head
appendages
• Leeches are dorsoventrally
flattened and tapered
anteriorly
• Anterior and posterior
segments have suckers
71. Locomotion
• Have lost metameric partitioning,
resulting in single body cavity
• Coelomic sinuses replace blood
vessels in most leeches
• Complex musculature (four types
of muscles)
• Move in looping motion or swim with
undulations
