Animal diversity 3 - The
Protostomes (Annelida, Mollusca,
Arthropoda)
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Key concepts
• What are the distinguishing characters and
life histories of the Annelida, Mollusca,
Arthropoda?
• There are LOTS more species in Arthropoda
than in any other phylum
• Learn what distinguishes the three subphyla
of arthropods: Chelicerata (scorpions,
spiders & mites), Crustacea (lobsters, crabs,
sowbugs & shrimp), Uniramia (insects,
millipedes, centipedes)
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Diversity of Annelida
But first…from last time
Examples of annelids?
Earthworms, Polychaete worms
(mostly marine forms), Leeches
How long can hatched Schistosoma eggs
survive to infect snails? Appears to be
only about 24 h
Latest on Trichinella and trichinosis
Not in cattle
Human-human transmission highly unlikely
In recent years, almost all cases have been
from wild game
A very few cases from recent Asian
immigrants - no trichinosis in Asia, so
consumption of rare or raw pork not
uncommon
Diversity of Annelida
Diversity of Annelida
True coelom!
Morphology
Mesoderm lines
body cavity and
Coelom - true
surrounds gut
coelom or
pseudocoelom?
Segmentation of body and coelom
Head w/ brain - more sophisticated
nervous system
Respiration across body wall
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Feeding
Earthworms?
Organic material in soil
Polychaete worms?
Parasites/predators/scavengers
Medicinal
leeches
Leeches?
blood! (mostly)
• ‘blood letting’ popular for centuries, fell
out of favor in mid 1800s
• recently leeches found to be very useful
in reattaching severed tissues
• anticoagulant in saliva prevents clotting,
allows veins to re-grow
• better than synthetic compounds which
act throughout the body, have side
effects
Diversity of Mollusca
Diversity of Mollusca
Very diverse - 110,000 species
(compare to ~ 30,000 vertebrates)
Examples?
Examples of mollusks without
shells?
Examples of mollusks without shells
include some of the most beautiful of all
animals, the slugs
…(the marine sea slugs - nudibranchs)
What’s the meaning of all the bright
colors?
Nudibranch defense with nematocysts
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Mollusca: Morphology
Mollusca: Morphology
Key adaptations the mantle & the radula
The mantle - sheet of skin
Secretes shell (when there is one), forms
gills for gas exchange, and in
cephalopods forms muscular cavity that
forcibly ejects water for locomotion
Key adaptations the mantle & the radula
The radula - a hardened tongue
Probably evolved for scraping algae off
rocks, and in different species has been
modified for puncturing, slicing,
manipulating food
Diversity of Mollusca
Diversity of Mollusca
Feeding niches
Mostly grazers (e.g. snails on algae)
or predacious
Feeding niches
Mostly grazers (e.g. snails on algae)
or predacious
amazing mollusk predators, the
cephalopods (Video segment)
Cephalopods
Cephalopods
Nautilus
Cuttlefish
Squid
Octopus
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Diversity of
Mollusca
Giant squid
Diversity of Mollusca
The cephalopods (e.g. squid,
cuttlefish, octopus, nautilus)
I. Giant squid - 60 ft long -the
largest invertebrate
Long been a
subject of
seafarers’
folklore
Diversity of Mollusca
The cephalopods (e.g. squid,
cuttlefish, octopus)
2004 - the first observations ever
of a giant squid in the wild!
i. Giant squid - 60 ft long - the
largest invertebrate
ii. giant axons - most highly developed
nervous system of invertebrates
iii. chromatophores - allow sudden
color changes for disguise, confusion
and courtship
iv. cephalopod intelligence
Diversity of Arthropoda “jointed feet”
Diversity of Arthropoda
General morphology
Some examples?
Jointed appendages
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Diversity of Arthropoda
Diversity of Arthropoda
General morphology
General morphology
Jointed appendages
Body is segmented
Jointed appendages
Body segmented
External (or exo-) skeleton
Diversity of
Arthropoda
Diversity of Arthropoda
What’s an exoskeleton good
for?
What are its drawbacks?
Diversity of Arthropoda
Three subphyla* Chelicerata, Crustacea, &
Uniramia
Limits to size
Diversity of Arthropoda
Chelicerata - scorpions, spiders
& mites
*(your book calls them phyla)
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Diversity of Arthropoda
Chelicerata - scorpions, spiders &
mites
Morphology
First set of appendages modified
into pincers or fangs
Feeding niches
Mostly predatory
but mites do almost everything herbivores, predators, parasites
Diversity of Arthropoda
Crustacea & Uniramia
First appendages antennae
Diversity of Arthropoda
Crustacea are the dominant marine
arthropods
any terrestrial crustaceans?
sowbugs
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