Animal Diversity: The invertebrates

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Animal Diversity The invertebrates
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Major Animal Phyla
Phylogeny of animal phyla based on DNA sequence
data
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Relative numbers animal species
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Types of animal symmetry
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Animal taxonomy based on presence or absence of
coelom (true body cavity)
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Herbivore
Carnivore
Omnivore
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Other feeding strategies
Basking sharks are suspension feeders
Earthworms are deposit feeders they eat decaying
organic matter
Gill rakers used to strain plankton from water
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Animal Phyla

• Porifera
• Cnidaria
• Platyhelminthes
• Nematoda
• Annelida
• Arthropoda
• Echinodermata
• Chordata

Invertebrates
Includes vertebrates
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Phylum Porifera, the sponges

• Approximately 5,000 marine spp., and about 150
  freshwater spp.
• No plane of symmetry, body shapes subject to
  change by waves, water currents

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• Sponge anatomy

Collar cell
Epithelium
Spicule
Pore
Spongin fibers are comparable to collagen fibers
of mammals
Spongin fiber
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Phylum Cnidaria
Cnidarians have radial symmetry
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Two general Body Forms of Cnidarians
Bell shaped
Cylindrical
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Some Cnidarians are either a polyp or a medusa,
and some alternate between medusa stage and polyp
stage
Another example of budding
Lifecycle of Aurelia
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Compass jellyfish
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Hydra sp.
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Sea anemones and corals are also polyps
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Cnidarians have true tissue layers but no organs
Mouth
Gastrodermis
Mesoglea
Tentacles
Epidermis
Sensory cell
Discharged nematocyst
Undischarged nematocyst
Hydra
Trigger
Stinging cell (cnidocyte) with nematocyst
Filament
Cnidarians capture prey using specialized
stinging cells called nematocysts
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Phylum Platyhelminthes, the flatworms
There are generally three types of flatworms
Tapeworms
Turbellarians
Flukes
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Turbellarians are free-living flatworms
The muscles allow complex movements
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Monogenean flukes are primarily ectoparasites of
fishes
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Life cycle of Chinese Liver Fluke
Digenean fluke are endoparasites of animals
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Tapeworms are parasites of the intestine
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Lifecycle of the pork tapeworm
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How do flatworms infect animals?

• Endoparasites must be consumed animals and
  people ingest an infecting larva stage
• Larva becomes an adult via metamorphosis
• Ectoparasite larvae swim to animals and attach to
  skin

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Phylum Nematoda
The vinegar eel is a small free living nematode
Free-living nematodes are important to the soil
by breaking it up, eating bacteria, plants, fungi
and helping to recycle nutrients
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Generalized Nematode Body Plan
Nematode Anatomy
Nematodes feature a complete digestive tract
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The amazing journey of Ascaris lumbricoides
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Lymphatic filariasis
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Phylum Mollusca

• Many are bilaterally symmetrical
• Possess a true body cavity known as a coelom
• Use an open circulatory system, organs bathed
  directly in blood
• Body covered by thick sheet of skin (like a
  cuticle), mantle cavity houses organs
• Shell glands of mantle secrete calcium based
  shell
• Well-defined muscular foot, often with a
  flattened creeping sole

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General Body Forms of Mollusks
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Mollusks are important to humanity for many
reasons
As a food source
As a source of disease
Shipworms destroy wooden boats
As a source of art and entertainment
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Some mollusks use a scraping organ (a radula) to
feed
A chiton
Rasping teeth of a radula
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Gastropod snails feature a coiled shell
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Bivalves feature a hinged shell
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Bivalves use the foot to settle into soft bottoms
water flow
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Cephalopods
squids
cuttlefishes
octopuses
nautiluses
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Some mollusks are very large
Architeuthis sp. (Giant squid)
Squid beaks are sometimes found in the stomachs
of sperm whales
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Phylum Annelida
Feather duster worm
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Earthworm anatomy
Earthworms have a complete circulatory system,
complete digestive system
Each segment has small hair-like structures
called setae
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A
B
C
D
Earthworms use hydrostatic locomotion similar to
the movement patterns of flatworms and nematodes
E
Circular muscles squeeze body segments, and
longitudinal muscles pull body segments
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Some Annelids have parapodia (fleshy appendages
with bristles)
This crawling mechanism is not seen in any other
worms
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Polycheates
Hydrothermal vent worms

• Worms absorb CO2 and H2S and transport it
  through the blood to symbiotic bacteria in its
  gut
• Bacteria use these chemicals to build
• organic matter which is used by the worm
• This is a symbiotic relationship called a
  mutualism

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Earthworm Mating and Cocoon Production
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Leeches are hirudineans ectoparasites of other
animals
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Phylum Arhtropoda
Arthropods have an exoskeleton and jointed
appendages they must periodically molt their
exoskeleton to grow
Dog-day cicada
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Arthropoda is the largest of all animal phyla
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Chelicerates vs. Mandibulates
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General body plan of an insect
Insects have three main body segments and
three pairs of walking appendages
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Some Arthropods have compound eyes
Light sensing organ
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How are compound eyes different from human eyes?
Compound eye
Camera eye

• One large lens
• Low degree of peripheral vision
• Can see far distances

• Many small lenses
• High degree of peripheral vision
• Cannot see far distances

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This is an important feature of terrestrial
arthropods
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General Body Plan of Arachnids
Arachnids have two main body segments and four
pairs of walking appendages
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Spiders (Chelicerata)
Black widow
Brown recluse
Progressive lesion from brown recluse bite
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Biramous (left) vs. Uniramous (right) Arthropod
Legs
Gills
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Carapace
General body plan of a crustacean cephalon (head)
and thorax often fused forming a cephalothorax
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Japanese giant spider crab crabby tough guy
Tough guy
Giant crab
Look Mommy, I peed my pants!
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Copepods are important members of many aquatic
communities
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Centipedes
Millipedes
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Insects
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Phylum Echinodermata
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Starfish anatomy
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ossicles
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tube feet
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Feather stars and sea lillies
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Sea urchin
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Sea cucumbers
Tentacles
Tube feet