Transcript File - Down the Rabbit Hole

INVERTEBRATES
Mollusca, Annelida, Arthropoda, Echinodermata
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Animals that lack vertebrae (classed by a characteristic they don’t have.)
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97% of all species on Earth are invertebrates.
Phylum Mollusca
©2004 Amanda Demopoulos
Phylum Mollusca
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•
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More species (200,000+) than any other
animal phylum except Arthropoda
Soft body – often protected by CaCO3
shell
Unsegmented, typically bilaterally
symmetrical
Mollusca: Major Characteristics
1.Cephalization
have a distinct
head with
sense organs &
brain (mostly)
2.Bilaterally
symmetrical
(mostly)
SNAIL, CLAM, CHITON, & SQUID
Basic Mollusk Body Plan
Head (eyes/sensory), visceral mass (organs), muscular foot
Mantle – covers visceral mass, secretes shell
Radula – Ribbon of small chitin teeth used in feeding
Gills (ctenidia-comb like) for gas exchange in mantle cavity
Radula – Ribbon of small chitin teeth used in feeding
4 Classes of Mollusca
1. Class Polyplacophora Many-plate-bearing = Chitons
800 species
• Mostly graze algae on rocky shorelines
• Exclusively marine
• 8 overlapping plates
2. Gastropoda
snails, slugs, nudibranchs,
conchs & abalone
Class Gastropoda
Most gastropods
are herbivores
Stomach-Foot
Stomach-Foot (class
Gastropoda) contains about
70% of all mollusk species. A
few stomach-foots are found
on land. The stomach-foot
include: snails, limpets and
abalones, which have shells.
Slugs and
nudibranchs are
also stomachfoots, but do not
have shells.
Abalones
Snails
Snails
Snails
Nudibranchs
3. Pelecypoda or Bivalvia
clams, oysters, & mussels
No head and no radula
Class Bivalvia
Most bivalves are
suspension feeders
Bivalvia Anatomy
Class Bivalvia
 Hinged, 2-valved shell
 (oysters, clams, mussels,
scallops) muscles keep closed
 No head , no radula
 Sedentary lifestyle
 Some have muscular foot for
burrowing (clams)
 Gills used for suspension feeding
& respiration
 Water enters and leaves
through siphons
 Some anchor to substrate
(mussels)
 Scallops – Swim! (repeated
clapping of valves)
4. Cephalopoda
squid, octopus, & nautilus
Class Cephalopoda
- Octopus and squid have beak-like jaws
- Mouth is central among tentacles
Octopus
8 arms, non-retractable w/ 2 rows of suckers
Nautilus
60-90 suckerless tentacles
Squid
8 arms + 2 tentacles nonretractable w/suckers and hooks
Cuttlefish
8 arms + 2 tentacles, retractable
w/ suckers, no hooks
Cephalopods
Octopuses are considered
among the most intelligent
invertebrates.
Chambered nautiluses are the only living
cephalopods with an external shell.
(b)
(a)
(c)
Squids are speedy carnivores
with beaklike
jaws and well-developed eyes.
Note the different shells in cephalopods external in Nautilus, internal in squids, and
missing in octopuses.
PHYLUM Annelida
Earthworms
Leeches
Tubeworms
Annelids: Major Characteristics
Segmented worms (1mm-3m)
•Body composed of repeated
segments
1. Cephalization
2. Bilateral symmetry
3. Coelom well developed and divided by
septa (except in leeches); coelomic fluid
supplies turgidity and acts as a
hydrostatic skeleton
Annelids: Major Characteristics
•Body wall
•Outer circular and inner longitudinal muscle
layers
•Protective elastic outer transparent moist
cuticle secreted by epithelium
•Closed circulatory system
•Respiratory gas exchange through skin, gills or
parapodia
•Digestive system of many has 2 openings,
mouth and anus (some have no gut)
•Excretory system
•Nervous systems
1. Polychaeta
Three Classes
Tubeworms, feather dusters, bristle worms, mainly marine
•Free-living predators
•Burrowing
•Tube building
Body segments have
pairs of parapodia
•
locomotion
•
feeding
•
gas exchange
•
protection
tipped with setae
(bristles), often 4
pairs
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Three Classes
2. Oligochaeta
• Earthworms, mainly
terrestrial and
freshwater
• Few marine species
• Benthic – mud and sand
(deposit feeders)
• No parapodia
• Locomotion – expansion
and contraction
Earthworm Anatomy
Annelid Movement
3. Hirudinea
Three Classes
•Leeches
•Hirudin – anticoagulating
chemical so blood does not
clot
•mainly freshwater but with
marine and terrestrial
species
•No parapodia
•One anterior/one
posterior sucker
Phylum Arthropoda
The vast
majority of
known animal
species,
including
insects,
crustaceans,
and arachnids,
are arthropods.
All arthropods
have segmented
exoskeleton and
jointed
appendages.
Phylum Arthropoda
• Most species of any phylum – over 1
million - 75% of all animals species
described
• Insects, spiders, centipedes, crabs,
lobsters, shrimp, barnacles, etc.
• Segmented, bilaterally symmetrical body
•Jointed appendages
•Exoskeleton made of chitin
•Growth requires molting - defenseless
• Body segments
•Head, thorax, abdomen
•Some groups have head and thorax
fused = cephalothorax
• Discuss 3 subphyla and representative
classes
1. Subphylum Chelicerata
A.
Class Merostomata
(=legs attached to mouth)
•
Horseshoe crabs-Not true crabs
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Named for feeding appendages – chelicerae
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Distinctive, horseshoe-shaped carapace
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No antennae
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Benthic predators/scavengers on clams and
small invertebrates
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No jaws - Grind food with bristles on walking
legs (must be walking to “chew”)
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Much of what we know understand about vision
based on horseshoe crab eyes
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Blood is used to test injectable
pharmaceutical solutions for bacterial
contamination
2. Subphylum Chelicerata
B. Class Pycnogonida (= thick
knees, Sea spiders)
• All marine
• Superficially resemble spiders
• Mouth at end of large proboscis
• Carnivores
•Feed on sea anemones,
hydrozoans,
•other soft inverts
• Legs much longer than body,
more than 8
2. Subphylum Chelicerata
C. Arachnida spiders,
scorpions, mites
• Largest class in Chelicerata
• Cephalothorax and abdomen
• Mouth called chelicerae
(first appendage
•Pinchers or fangs
• Pedipalps
•Second pair of appendages
•Handle prey, sensory
• Four pair of walking legs
2. Subphylum Chelicerata
Arachnids
Chelicerae
are feeding
appendages
PHOTO: Bill Rudman
Cheliceriform Anatomy
Class Trilobita
•Marine
•Extinct since 250
mya
•Rich fossil history
because of
exoskeleton
•Dorso-ventrally
flattened
3. Subphylum Crustacea (40K species)
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Contains majority of marine arthropod species
Gills + two pairs of antennae (sensory)
Larval forms – nauplius and zoea
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Extremely abundant holoplankton (always plankton)
Some live on/in substrates (benthos)
**Among most abundant animals on earth**
Important primary consumers of phytoplankton
Small << 1-2 mm
Some parasitic forms
A. Class Copepoda (=oar foot, Copepods)
3. Subphylum Crustacea
B. Class Cirripedia (= hairy foot,
Barnacles)
•Active suspension feeders (filter
feeders)
•Use feathery cirri (modified
swimming appendages)
•Sessile (attached to surfaceswhales, piers)
•Fouling organisms (boats, whales)
•Resemble mollusks superficially –
calcareous plates
3. Subphylum Crustacea
C. Class Malacostraca (=soft shell,
75% crustacean species-Discuss 4
Orders)
1. Order Amphipoda (Amphipods)
beach hoppers, sand fleas, whale
lice
• Laterally compressed
•Generally
small (< 2 cm), but
larger in deep ocean
•Head
and tail downward
• Widespread distribution
•Generally
free living
•Important
scavengers
3. Subphylum Crustacea
C. Class Malacostraca
2. Order Isopoda (Isopods-rock
lice, fish lice)
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Dorsoventrally compressed
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Generally small (< 2 cm), but
larger in deep ocean
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Related to terrestrial pill
bugs
Widespread distribution
Generally free living
Important scavengers
Some parasites
3. Subphylum Crustacea
C. Class Malacostraca
3. Order Euphausiacea (Krill) holoplankton
•Laterally compressed
•Up
to 10 cm long (usually smaller)
•Head and anterior segments fused to form
distinct carapace
•Widespread distribution
•Important
primary consumers and predators
•Important
prey for larger consumers
(whales, penguins, fish)
•Keystone
species in some ecosystems (Polar,
Southern Ocean)
•Aggregate in schools (billions of individuals)
3. Subphylum Crustacea
C. Class Malacostraca
4. Order Decapoda (=10 legs, Crabs,
Lobsters, Shrimps)
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Most species in Crustacea
(~10,000)
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Scavengers/Predators/Both
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Largest crustaceans
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Five pairs of walking legs (deca=10)
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First pair usually modified as
claws for feeding/defense
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Well-developed carapace =
cephalothorax
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Rest of body = abdomen, tail
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Laterally compressed, except
crabs – abdomen under
cephalothorax
Fig. 7.30
4. Subphylum-Uniramia
A. Class Insecta = Hexapoda (6
footed)
• 1 million species described to
date
• Found in every known terrestrial
+ freshwater habitat, some
marine except deep sea
• Diversity attributable to
• Feeding specialization
• Dispersal capabilities
• Predator-avoidance
possibilities (flight)
4. Subphylum-Uniramia
A. Class Insecta = Hexapoda (6 footed)
Tracheal tubes are used
in gas exchange
Insect wings
are modified
cuticle, not
appendages
“Insects are more
species rich than all
other forms of life
combined.”
Insect Anatomy
Complete Metamorphosis
In incomplete metamorphosis (not shown),
the juvenile looks like the adult
4. Subphylum-Uniramia
A. Class Diplopoda = 2 pair of legs per segment = millipedes
B. Class Chilopoda = 1 pair of legs per segment = centipedes
Millipedes, herbivores,
were perhaps the first
land animals
Centipedes are
carnivores
Phylum Echinodermata
Echinoderms, such
as sand dollars,
sea stars, and sea
urchins, are aquatic
animals that display
radial symmetry as
adults. They move
and feed by using a
network of internal
cannals to pump
water to different
pars of the body.
Phylum Echinodermata
 “Spiny skin” 6000 species
Sea lilies, feather stars,
brittle stars, sea stars, sand
dollars, sea urchins, sea
biscuits, sea cucumbers
Radial symmetry
Endoskeleton = hard plates,
~95% calcium carbonate,
covered by skin
Complete digestive, nervous
systems, and reproductive
organs
Regeneration
Water vascular system =
internal hydraulic system
Sea Stars
Sea stars
posses
multiple arms,
upon which
are numerous
tube feet, and
a calciferous
endoskeleton
Phylum Echinodermata
Tube feet (podia)
extended by pressure
from ampullae (muscular
sacs)
Tube feet used for
locomotion, feeding,
sensory functions
Phylum Echinodermata
Crown of Thorns
Acanthaster planci
Echinoderm Anatomy
The End