Transcript Annelids, Mollusks and Arthropds

Chapter 35
Section 35.1
Video
 Means
“soft body”
 Most marine, some freshwater, a few
terrestrial
Terrestrial
Fresh Water
Marine
 Definition:
a body cavity that is completely
lined by mesoderm and contains internal
organs
 Found
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in the following phlya:
Mollusca (clams)
Arthropoda (crayfish)
Echinodermata (starfish)
Chordata (humans)
Annelida (earthworms)
 Trochophore:
larval stage of development for
aquatic mollusks and annelids

Use cilia for swimming and feeding
 Some
have a hard shell for protection
 Body
divided into 2 main section: headfoot & visceral mass:
 Head-foot:
head (mouth, sensory
structures) and foot (locomotion)
 Visceral
mass: heart & digestive,
excretion, and reproductive organs

Covered by the mantle
 Mantle:
layer of epidermis that excretes a hard
shell of calcium carbonate
 Mantle cavity: space between mantle and
visceral mass that protects the gills
 Ganglia: clustered nerve cells that control
locomotion & feeding
 Radula: flexible, tongue-like strip of tissue
covered with abrasive teeth
Video
• radula – rasping “tongue” of chitin
1.
2.
3.
Class Gastropoda
Class Cephalopoda
Class Bivalvia
(Snails, nudibranchs, cowries, whelks)
 Largest
and most diverse group of mollusks
 Examples: snails, abalones, conchs, slugs
 Locomotion: wavelike muscular contractions on
mucus slime trail
 Can withdraw head into mantle cavity when
threatened
Video
 Hemolymph:
 Hemocoel:
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circulatory fluid
fluid filled spaces
A.k.a. blood cavity
tentacles- sense touch & have
eyes on ends
 respire with gills (aquatic) or
exposed blood vessels
(terrestrial) by diffusion
 we eat muscular foot
“escargot”

• shoot, then inseminate
• (mucus paralyzes female
reproductive tract)
• successful darters double success
 Examples:
octopuses, squids, cuttlefishes,
chambered nautiluses
 Marine animals, free swimming
 Meaning “head-foot”
 Tentacles
have large suction cups
 Largest invertebrate brain
 Highly advanced eyes similar to humans
 Closed circulatory system
 Many release dark, inky fluid when alarmed
 Many have pigment cells called
chromatophores for camouflage
Video
Squid, chambered nautilus, cuttlefish, octopus
Video
 Examples:
clams, oysters, mussels, scallops
 All have a two part shell connected by hinge
closed by adductor muscles
 aged by shell rings
 sedintary
 filter feeders
Video
2
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siphons at the posterior end:
Incurrent siphon = intake of water & food
Excurrent siphon = output of water & wastes
 Clams
dig in the soil so only their siphons
stick out

Filters about 3 quarts an hour!
Video
Video
 Calcium
carbonate secretion around a
foreign object
Protection of the soft visceral mass
 Made by the mantle (just like the shell)

 -----------
protective outer layer

 /////////////
 -----------
prismatic layer
pearly layer
He Was Shellfish
Body parts you MUST identify & show me during
the lab:
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Umbo
Valves (shells)
Mantle
Gills
Incurrent & excurrent siphons
Palps & mouth
Digestive gland
Intestine
Gonads
Heart
clam

Oldest part
DORSAL
ANTERIOR
POSTERIOR
VENTRAL
Section 35.2
 Examples:
earthworms, leeches
 Annelid means “Little rings”
 Segmentation allows for division of labor
 Bilateral symmetry
 Live in freshwater, marine water, and
terrestrial environments
 Setae:
external bristles
 Parapodia: fleshy protrusions on outside of body
 Number
of setae and parapodia divides this
phylum into three class:
1.
2.
3.
Class Polychaeta
Class Hirudinea
Class Oligochaeta
 “Many
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bristles”
Number of setae and parapodia
 Have
anetennae & specialized mouth parts
 Most are marine animals

Trochophore larvae
 Predatory
 Largest
class of annelids
Video
 Smallest
class of annelids
 Example: leeches
 Live in calm freshwater & moist vegetation
 No setae or parapodia
 Most are carnivores & some are parasitic
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Secrete anaestheic & anticlotting factors
Ingest 10 times it own weight in blood!
 “Few

bristles”
Few setae and no parapodia
 Live
in soil or freshwater
 Example: earthworms
 Divided
into over 100 segments
 Movement:
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Anchor middle segments with setae
Contract muscles in front
Elongation of anterior
Setae of anterior grip ground
Pull posterior forward
 Ingest
soil as they burrow
 Digestion path: mouth  esophagus  crop
(temp. storage)  gizzard (releases & breaks
up organic matter)  long intestine
(absorption of nutrients)  anus
 Closed
circulatory system
 Ventral (toward posterior) & dorsal (toward
anterior) vessels
 Aortic arches link ventral and dorsal vessels
 Respiration:
diffusion of oxygen and carbon
dioxide via moist skin
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Secretion of mucus to keep moist
 Excretion:
via nephridia (excretory tubules in
every segment except first three)
 Chain
of ganglia connected by a ventral nerve
cord
 Each segment has a single ganglia
 Brain = fused ganglia
 Simple sensory skills
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Light
Touch
Chemicals
temperature
 Hermaphrodites
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Cannot fertilize own self
 Mating:
press ventral surfaces together,
anterior ends pointed opposite directions
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Setae hold worms together
Mucus secretion from clitellum
Each worm injects sperm into mucus
Sperm going into seminal receptacles of other
worm
Several days later chitin tube forms picking up
eggs & stored sperm  fertilization
Young worms develop inside tube and hatch 2-3
 Decomposers
of leaves and organic matter
 Recycle nutrients
 Release natural fertilizers (waste)
 Aerates the soil