Download Protostomes

32
Protostome
Animals
32 Protostome Animals
• 32.1 What Is a Protostome?
• 32.2 What Features Distinguish the Major
Groups of Lophotrochozoans?
• 32.3 What Features Distinguish the Major
Groups of Ecdysozoans?
• 32.4 Why Are Arthropods So Diverse?
32.1 What Is a Protostome?
Two triploblastic clades of Bilateria: protostomes and
deuterostomes diverged in Cambrian, over 505 mya
 Protostomes have far more species and individuals
 In most, embryonic blastopore becomes mouth
 In insects, no blastopore forms
www.emc.maricopa.edu/faculty/farabee/BIOBK
Figure 31.1 The Phylogeny of Animals
32.1 What Is a Protostome?
Two major clades of
protostomes mostly
based on DNA
sequences:
 Lophotrochozoans
 Ecdysozoans
Figure 32.1 Phylogenetic Tree of Protostomes (Part 1)
Figure 32.1 Phylogenetic Tree of Protostomes (Part 2)
32.1 What Is a Protostome?
Other general characters of protostomes
 bilaterally symmetrical
 anterior brain that surrounds the entrance to
digestive tract
 ventral nervous system with paired or fused
longitudinal nerve cords
http://organicwaste.com.au/wpcontent/uploads/2009/06/earthworm-anatomy.gif
32.1 What Is a Protostome?
Common ancestor had a coelom, but some
lineages have modifications:
 Flatworms are acoelomate (coelom was lost)
 Some lineages have pseudocoelom
 Arthropods — the body cavity became a
hemocoel or blood chamber, part of an open
circulatory system
http://science.kennesaw.edu/~jdirnber
/InvertZoo/Tree/coelom.jpg
32.1 What Is a Protostome?
 Mollusks have an open circulatory system
similar to the hemocoel but retain vestiges
of an enclosed coelom
http://kentsimmons.uwinnipeg.ca/16cm05/
1116/33-16-MolluskBodyPlan-L.gif
32.1 What Is a Protostome?
Lophotrochozoans
 Several groups have a
lophophore
circular or U-shaped ridge
around mouth with two
rows of hollow, ciliated
tentacles
 Functions in food
collection and gas
exchange

http://bioweb.uwlax.edu/zoolab/Table_of_
Contents/Lab-6a/Phylum_Ectoprocta_2
32.1 What Is a Protostome?
Lophophores appear to have evolved
independently several times; or it is ancestral and
has been lost by some groups
 Nearly all animals with a lophophore are sessile
as adults (bryozoans, brachiopods, phoronids)

Black Phoronid Worm
(Phoronis australis)
www.scuba-equipment-usa.com/marine/DEC04/images
Figure 32.2 Bryozoans Use Their Lophophore to Feed
A bryozoan with
extended
lophophores
32.1 What Is a Protostome?
Some lophotrochozoans have
a trochophore larval form
 Moves by beating a band of
cilia
 Also brings plankton closer
where they can be captured
and ingested
 Found in Mollusks, annelids,
ribbon worms, and
bryozoans...
 It is probably ancestral, but
secondarily lost in some
groups
Trochophore of the Ass's-ear
abalone, Haliotis asinina
http://upload.wikimedia.org/wikipedia/commo
ns/c/cb/Haliotis_asinina_trochophore.jpg
Figure 31.11 Planktonic Larval Forms of Marine Animals (A)
32.1 What Is a Protostome?
Some lophotrochozoans have spiral cleavage
(flatworms, ribbon worms, annelids, mollusks)
 Many are worm-like  good shape for burrowing
into soft sediments
 Mollusks are most species-rich group, and have
very different body plan
Photo 32.9 Family
Nereidae: the clam worm
(Nereis succinea).
32.1 What Is a Protostome?
Ecdysozoans
 cuticle secreted by epidermis
(outermost cell layer)
To grow, exoskeleton must be
shed or molted, and replaced
with a larger one
 Before molting, new exoskeleton
is already forming
 After old one is shed, new
exoskeleton expands and
hardens

32.1 What Is a Protostome?

Before it hardens, animal is
vulnerable to predators –
exoskeleton is soft and
animal cannot move much

Molting evolved 500 million
years ago, apparently only
once  thus ecdysozoans
are monophyletic (have
single common ancestor)
Centruroides gracilis molting
http://johnbokma.com/mexit/2006/03/23/centruroides-gracilis-molting-2.jpg
Figure 32.3 Molting: Past and Present
32.1 What Is a Protostome?
 In some worm-like ecdysozoans the
cuticle is thin and flexible

A thin cuticle allows gas and water
exchange, but restricts animal to moist
habitats.
Photo 32.42 Unidentified
free-living marine
nematode collected from
the North Sea. LM.
32.1 What Is a Protostome?
In other ecdysozoans, mainly
arthropods, the cuticle is an
exoskeleton, thickened by
proteins and chitin, a
waterproof polysaccharide.
 The thick exoskeleton
restricts movement and gas
exchange;
 New mechanisms for these
things evolved
Photo 32.93 Family
Asilidae: robber fly
(species undetermined).
32.1 What Is a Protostome?
 Appendages manipulated by muscles
evolved in the late Precambrian,
leading to the arthropod (―jointed
foot‖) clade.

Appendages are used for locomotion,
food capture, gas exchange, copulation,
and sensory perception.
The sea spider
(Nymphon gracile)
32.1 What Is a Protostome?
Muscles are attached to the inside of the
exoskeleton  each segment has muscles that
operate that segment and the appendages
attached to it
 The hard exoskeleton allowed for walking on dry
land, and prevented drying
 Aquatic arthropods were excellent candidates to
invade land

Figure 32.4 Arthropod Skeletons Are Rigid and Jointed
32.1 What Is a Protostome?
http://www.cmarz.org/CMarZ_Cruise_April/images_press/Eukrohnia_sp1b.jpg
Jump to
Slide #31
Arrow worms - Chaetognaths
 Evolutionary relationships
have been long debated
 NOT considered
lophotrochozoans here
 Early development similar
to deuterostomes, but
these are features
ancestral to all
triploblastic animals
Eukrohnia sp.
32.1 What Is a Protostome?
http://www.cmarz.org/CMarZ_Cruise_April/images_press/Eukrohnia_sp1b.jpg
Arrow worms:
 Gene sequences have
identified them as
protostomes
 may be sister group to
all other protostomes
Eukrohnia sp.
Figure 32.5 An Arrow Worm
32.1 What Is a Protostome?
Arrow worm coelom is
divided into three
compartments
 body is transparent
 most swim in open sea,
others live on sea floor
 Major predators of small
planktonic organisms
 Abundant as fossils from
500 million years ago.
32.1 What Is a Protostome?
Arrow worms have no circulatory
system
 wastes and nutrients are moved
around in coelomic fluid,
propelled by cilia that line
coelom
 No larval stage (direct
development)

Miniature adults hatch from eggs
that are fertilized internally
following elaborate courtship
between two hermaphroditic
individuals
Cephalic spines, or hooks,
for capturing prey
32.2 What Are the Major Groups of Lophotrochozoans?
Bryozoans or ―moss animals‖
 A.k.a. Ectoprocts
 Bryozoans are colonial
Jump to
Slide #37
32.2 What Are the Major Groups of Lophotrochozoans?
The external body wall secretes material that
forms a ―house‖
 Individuals are 1–2 mm in size, and connected
by strands of tissue
Plumatella fungosa
http://www.senckenberg.de/images/content
/forschung/abteilung/aquazool/mev3/
Plumatella sp.
http://www.plingfactory.de/Science/Atlas/K
ennkartenTiere/Bryozoa/Image
32.2 What Are the Major Groups of Lophotrochozoans?
 Colony is created by asexual reproduction by
founding member.
 Colonies may contain as many as 2 million
individuals
Photo 32.37
Freshwater bryozoan
(Cristatella mucedo).
Figure 32.6 An Ectoproct Colony
32.2 What Are the Major Groups of Lophotrochozoans?
Individuals can rotate lophophore to
increase contact with prey; also retract it
32.2 What Are the Major Groups of Lophotrochozoans?
Ectoprocts reproduce sexually
 Sperm is released into the water and carried to
another individual.
 Eggs are fertilized and brooded internally, then
larvae released to find new attachment sites
Colony and zooids of Selenaria mutabilis from
Australia tertiary rock. Right: male zooid (top),
brooding zooids (centre, upper right)
www.civgeo.rmit.edu.au/bryozoa/cheilostomata/selenariidae
Cyphonautes larva of
Membranipora sp.
http://life.bio.sunysb.edu/marinebio
32.2 What Are the Major Groups of Lophotrochozoans?
Flatworms and rotifers form a monophyletic
group, even though they have different body
plans
Photo 32.5 Freshwater
rotifer (Asplanchna sp.). LM.
32.2 What Are the Major Groups of Lophotrochozoans?
Flatworms (Platyhelminthes)
 Acoelomates
 Lack system for gas transport
 Every cell must be near
surface  accomplished by
dorsoventrally flattened
body
32.2 What Are the Major Groups of Lophotrochozoans?
 Digestive tract is mouth opening into a blind
sac (gastrovascular cavity)
cavity is often highly branched — increases
surface area for absorption of nutrients
 Feeds on animal tissue – dead or alive

Photo 32.1 Freshwater
planarian (Dugesia sp.),
showing bilateral symmetry
and gut ramifications.
32.2 What Are the Major Groups of Lophotrochozoans?
 Simple organs for
excreting metabolic
wastes (flame cells)

First animals to show
dedicated excretory
system
Figure 32.7 Flatworms May Live Freely or Parasitically
32.2 What Are the Major Groups of Lophotrochozoans?
Turbellarians
 Small, free-living flatworms
 glide over surfaces by broad bands of cilia
 have cephalization
 Chemoreceptor organs
 Simple eyes
 Small brain
32.2 What Are the Major Groups of Lophotrochozoans?
Most flatworms are internal parasites
 Cestoda – tapeworms
 Trematoda – flukes
 They absorb digested food from digestive
tract of host
Photo 31.39 Parasitic
sheep liver fluke
(Fasciola hepatica).
32.2 What Are the Major Groups of Lophotrochozoans?
 The monogeneans are external
parasites of fish and other aquatic
organisms
Monogenean parasite
on gill of a grouper
http://www.uen.org/utahlink/tours/admin/tour/18753/18753monogenea.gif
Simple Lophotrochozoans
 Some species cause serious diseases, e.g.
schistosomiasis (fluke infects liver, intestine and
bladder in humans)

This species has a complex life cycle involving freshwater
snails and mammals as hosts.
www.afids.org
www.schisto.org/Schistosomiasis/images
www.correodelmaestro.com/
anteriores/2005/marzo/fotos
Adult pork tapeworm, Taenia solium
(Cestoda), from the intestine of a
human. See scolex on head for
attachment and gravid proglottid.
www.emc.maricopa.edu/faculty/farabee/BIOBK
www.medizin.de/gesundheit/data_images/low
Reaching a Host by a Complex Route
Most parasitic flatworms have complex life cycles
 Involve one or more intermediate hosts
 Several larval stages
32.2 What Are the Major Groups of Lophotrochozoans?
Rotifers
 tiny (50–500 m), but have
specialized internal organs
 Complete gut
 Body cavity is pseudocoel
that functions as
hydrostatic skeleton, but
most propel themselves by
cilia
 About 1,800 species, most
in freshwater
http://carnegieinstitution.org/first_light
_case/horn/schools/hart/images
32.2 What Are the Major Groups of Lophotrochozoans?
Corona
 ciliated organ on head
 Beating cilia sweep food
particles into mouth and into
mastax, organ that grinds
food
 Some can protrude mastax
through mouth and capture
prey with it
Figure 32.8 Rotifers
32.2 What Are the Major Groups of Lophotrochozoans?
Bdelloid rotifers have only females
 Eggs develop without fertilization
(parthenogenesis)
 They may have existed for millions
of years without sexual
reproduction, which usually leads
to build-up of deleterious
mutations and extinction
 They may pick up fragments of
genes from their environment
during a desiccation–rehydration
cycle
www.news.cornell.edu/photos
32.2 What Are the Major Groups of Lophotrochozoans?
Nemerteans – ribbon worms
Carnivorous
 Complete digestive tract
Jump to
Slide #61
32.2 What Are the Major Groups of Lophotrochozoans?
 have fluid-filled cavity
called rhyncocoel
 inside is hollow,
muscular proboscis
 Muscle contractions
cause the proboscis
to be expelled
explosively from an
anterior pore  may
be armed with sharp
stylets to pierce prey
and release toxins.
Figure 32.9 Ribbon Worms
32.2 What Are the Major Groups of Lophotrochozoans?
Phoronids and brachiopods have
lophophores that probably evolved
independently from bryozoans
32.2 What Are the Major Groups of Lophotrochozoans?
Phoronids are small, sessile, marine worms
 Secrete a tube of chitin in which they live
Colonial mass of phoronids
living in a clam shell. Bright
white objects are embryos
being protected in the bases of
the lophophores (about 0.1
inch across).
www.reefkeeping.com/issues/2002-12/rs/images
32.2 What Are the Major Groups of Lophotrochozoans?
 In most species, eggs released into water and
fertilized there
 in a few species eggs are fertilized and
brooded internally
Black Phoronid worm
(Phoronis australis)
http://www.scuba-equipmentusa.com/marine/DEC04/images/Phoronis_australis.jpg
Figure 32.10 Phoronids
32.2 What Are the Major Groups of Lophotrochozoans?
Brachiopods
 Solitary, marine animals
 Two-part shells connected by ligament
 Superficially resemble bivalve mollusks, but shell
evolved independently
 two halves of shell are dorsal and ventral,
bivalves are lateral
Figure 32.11 A Brachiopod’s Lophophore
32.2 What Are the Major Groups of Lophotrochozoans?
http://life.bio.sunysb.edu/marinebio/larv_16.jpg
 Brachiopods live attached
to substrate – some
species have stalk
 Gametes released into
water for fertilization –
larvae are planktonic
 Brachiopods reached
peak abundance in
Paleozoic and Mesozoic
 Only 355 species survive.
Disconiscid
larva of an
Articulate
Brachiopod
Lingula sp.
http://paleo.cortland.edu/tutorial/Brachiopods
32.2 What Are the Major Groups of Lophotrochozoans?
Annelids and mollusks are closely related
Photo 32.12 Annelid,
Serpula vermicularis.
Photo 32.19 Mollusk, Mytilus edulis
32.2 What Are the Major Groups of Lophotrochozoans?
Annelids have segmented
bodies
 Coelom in each segment
is isolated from coelom in
other segments by septa
 Separate nerve
ganglion controls each
segment
 Most have a thin,
permeable body wall that
serves for gas exchange
 restricted to aquatic or
moist habitats.
Figure 32.12 Annelids Have Many Body Segments
32.2 What Are the Major Groups of Lophotrochozoans?
Polychaetes
 mostly marine; many burrow in soft sediments
 One or more pairs of tentacles for filter feeding
and gas exchange
Photo 32.9 Family Nereidae: the
clam worm (Nereis succinea).
Spirobranchus giganteus
(Christmas Tree Worm)
www.cs.brown.edu/people/twd/fish/Curacao
Figure 32.13 Diversity among the Annelids (A)
32.2 What Are the Major Groups of Lophotrochozoans?
 Parapodia
Extensions of the body wall on each segment
 Function in gas exchange, sometimes for
movement
 Many setae – stiff bristles protude from
parapodia to ―hold‖ onto substratum

www2.nrm.se/ev/images/
ttp://tolweb.org/tree/ToLimages
Diversity among the Annelids (A)
32.2 What Are the Major Groups of Lophotrochozoans?
www.dfo-mpo.gc.ca/communic/endeavour
Pogonophorans
 polychaetes that have
lost their digestive tract
 Secrete tubes of chitin in
which they live
 Discovered in twentieth
century in deep oceans,
living at high densities
 Largest up to 2 meters
long and live near
hydrothermal vents
Pogonophorans around a
“black smoker”
http://www.calacademy.org/exhibits/xtremelife/images/smoker_great.jpg
32.2 What Are the Major Groups of Lophotrochozoans?
 Take up dissolved organic
matter from substrate,
facilitated by endosymbiotic
bacteria in specialized
organ called trophosome
 endosymbiotic bacteria fix
carbon using energy from
oxidation of H2S
(chemoautotrophic
bacteria)
http://microbezoo.commtechlab.msu.edu/zoo/microbes/media/riftiasym.jpg
Figure 32.13 Diversity among the Annelids (B)
32.2 What Are the Major Groups of Lophotrochozoans?
Clitellates are freshwater or
terrestrial — oligochaetes
and leeches
Oligochaetes
 lack parapodia, eyes, or
tentacles, and few setae
 Earthworms burrow in and
ingest soil
 Many aquatic or marine
Freshwater
oligochaete with
diatoms in gut
www.microscopy-uk.org.uk/mag/imgsep03
32.2 What Are the Major Groups of Lophotrochozoans?
 All oligochaetes are hermaphroditic (both
male and female)

Each individual gives and receives sperm
during copulation
Earthworm cocoons
or egg cases
www.ens-newswire.com/ens/pics25
Figure 32.13 Diversity among the Annelids (C)
32.2 What Are the Major Groups of Lophotrochozoans?
Hirudinea – Leeches
 Lack parapodia and tentacles
 Coelom not divided into
compartments
 Segments at either end are
modified to form suckers —
temporary anchors that aid in
movement
 Leeches are freshwater and
terrestrial
Figure 32.13 Diversity among the Annelids (D)
32.2 What Are the Major Groups of Lophotrochozoans?
 Leeches make incision in host, and secrete
anticoagulant (hirudin) into wound.
Medicinal leeches were used to treat diseases believed
to be caused by excess blood or ―bad blood‖
 Hirudo medicinalis is still used today to treat wounds
and prevent scarring

Myzobdella lugubris, parasitic leech of fish
http://hbs.bishopmuseum.org/good-bad
www.travelgolf.com/images/features
www.studentbmj.com/back_issues/0898
Mouth of the
bloodsucking
medicinal leech
( this is real)
www.monsterlandtoys.com/video
www.paulcampion.com/productionDesign/images
32.2 What Features Distinguish the Major Groups of
Lophotrochozoans?
Mollusks
 most diverse group of lophotrochozoans
http://www.palaeos.com/Invertebrates/Molluscs/Images/mollusc_classes.jpg
32.2 What Are the Major Groups of Lophotrochozoans?
http://www.ucmp.berkeley.edu/taxa/inverts/mollusca/mollusca.php
Mollusk body plan has three main
components – foot, visceral mass, mantle
 Often the foot and mantle are greatly modified
California Trivia snail (Trivia californiana)
and the Giant Squid (Architeuthis).
32.2 What Are the Major Groups of Lophotrochozoans?
 Foot
large, muscular structure, originally for
locomotion and support of internal organs
 modified in different groups

Photo 32.26 Family
Mitridae: triplet of Ida's
miter (Mitra idae); Point
Lobos, CA.
32.2 What Are the Major Groups of Lophotrochozoans?
 Visceral mass

includes heart, digestive, excretory, and
reproductive organs
32.2 What Are the Major Groups of Lophotrochozoans?
Mantle
 tissue fold covering
organs in visceral mass
 Mantle secretes the
calcareous shell
 In most species, mantle
extends beyond visceral
mass to form a mantle
cavity
 Within cavity are gills
for gas exchange
Cypraea cribraria, the seive cowry
with mantle partially extended
www.this-magic-sea.com/IMAGES
Figure 32.14 Organization of Molluscan Bodies (Part 1)
32.2 What Are the Major Groups of Lophotrochozoans?
Gills
 Cilia on gills beat to
create a water
current
 Water current may
enter/exit via siphon
 Gills are highly
vascularized (many
blood vessels) for
gas exchange
http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/Bio%20102/Bio%20102%20lectures/Animal%20Diversit
y/Protostomes/Lophotrochozoans/clam2.jpg
http://www.ucmp.berkeley.edu/images/taxa/inverts/snailrad600.jpg
32.2 What Are the Major Groups of Lophotrochozoans?
Feeding
 Some species use gills
for filter feeding (most
bivalves)
 others have radula –
rasping structure for
scraping algae from rocks
(chitons, gastropods)
Radula of Sinistral Pond
Snail (Physella sp.)
SEM of radula of Turnip
whelk, Busycon coarctatum
www.jaxshells.org/
32.2 What Are the Major Groups of Lophotrochozoans?
Most mollusks have open
circulatory system
(except cephalopods)
 Blood and fluids empty
into hemocoel…
 where oxygen is
delivered to internal
organs
 Blood eventually reenters blood vessels
and is pumped by a
heart
http://www.esu.edu/~milewski/intro_biol_two/lab__11_mollusca/images/bivalve_circulatory.jpg
32.2 What Are the Major Groups of Lophotrochozoans?
Monoplacophoran
 Most abundant mollusks during Cambrian, but
only a few species survive
 Resemble limpets, but in contrast to all other
living mollusks, organs are repeated (as if
segmented) over length of the body
Tryblidia sp.
www.conchasbrasil.org.br/materias/monoplacophora
32.2 What Are the Major Groups of Lophotrochozoans?
Polyplacophorans – Chitons
 Have multiple gills and shell plates, but other
parts not segmented
 Most marine herbivores that scrape algae with
radula
 Cling tightly to rock surfaces with large, muscular
foot
Lined chiton,
Tonicella lineata
www.palaeos.com/Invertebrates/Molluscs/Polyplacophora/Images
Figure 32.15 Diversity among the Mollusks (A)
32.2 What Are the Major Groups of Lophotrochozoans?
http://upload.cnd.org/uploads/dir3/geoduck_gaper_clams.jpg
Class Bivalvia
 clams, oysters, scallops,
mussels.
 hinged, two-part lateral
shells
 Many use foot to burrow
into mud or sand
 Feed by bringing water in
incurrent siphon, filtering
food particles with large
gills, water exits through
excurrent siphon
Geoduck clam
Tridacna derasa, the
smooth giant clam
http://www.richard-seaman.com/Underwater/Australia/GiantClams/TridacnaCroceaOrDerasa.jpg
Figure 32.15 Diversity among the Mollusks (B)
Siphon
32.2 What Are the Major Groups of Lophotrochozoans?
Class Gastropoda
snails, slugs, nudibranchs (sea
slugs), limpets, abalones
Photo 32.24
Family Trochidae:
jewelled topshell
(Calliostoma
annulatum).
32.2 What Are the Major Groups of Lophotrochozoans?
 Most move by gliding on foot, but in
few species foot is a swimming organ
Spanish Dancer (Hexabranchus sp.)
http://www.divegallery.com/Spanish_Dancer.jpg
32.2 What Are the Major Groups of Lophotrochozoans?
 Nudibranchs
Gastropods that have lost shell
 many are toxic and have brilliant colors for
warning – aposematic coloration

32.2 What Are the Major Groups of Lophotrochozoans?
 Shelled gastropods
have one-piece shells
 Land snails and slugs
are only mollusks that
live in terrestrial
habitats

Florida apple snail
(Pomacea paludosa)
mantle tissue is
modified into highly
vascularized ―lung‖
http://www.sanybel.com/Newsletter-Apple_Snail.jpg
Figure 32.15 Diversity among the Mollusks (D)
32.2 What Are the Major Groups of Lophotrochozoans?
Class Cephalopoda
 squids, octopuses, and
nautiluses
 excurrent siphon is modified
 forcibly ejects water from
body cavity, allowing them
to move by ―jet propulsion‖
 Became dominant marine
predators in the Devonian
 Unlike other molluscs, has
closed circulatory system for
active lifestyle
Photo 32.32 Adult
cuttlefish (Sepia
officinalis), captive.
Figure 32.15 Diversity among the Mollusks (E)
Caribbean Reef Squid
(Sepioteuthis sepioidea)
http://www.reefnews.com/reefnews/news/v06/v06n06/olblue12.jpg
32.2 What Are the Major Groups of Lophotrochozoans?
 Tentacles are used to capture and subdue prey
 octopuses also use them to move over the
substratum.
Walking octopus
Squid with fish
http://farm3.static.flickr.com/2280/2191568056_099e1e3727.jpg?v=0
http://static.howstuffworks.com/gif/octopus-6.jpg
32.2 What Are the Major Groups of Lophotrochozoans?
http://wild-facts.com/wp-content/uploads/2010/08/deep-sea-glass-squid.jpg
 Cephalopods’ head with
complex sensory organs
Eyes are comparable to those
of vertebrates
 Head is associated with a large,
branched foot that bears
tentacles

 Many early cephalopods had
chambered shells; Nautilus is
the only one with an external
chambered shell today
Deep sea glass squid
Figure 32.15 Diversity among the Mollusks (F)
32.3 What Are the Major Groups of Ecdysozoans?
Ecdysozaons three main
clades that exhibit a
progression in their
exoskeleton that molts as
they grow…
 Thin cuticle
 Thicker, multi-layered
cuticle
 Rigid, chitinous
exoskeleton
32.3 What Are the Major Groups of Ecdysozoans?
Priapulids, kinorhynchs,
and loriciferans are wormlike marine ecdysozoans
with thin cuticles that are
molted as animal grows
32.3 What Are the Major Groups of Ecdysozoans?
Embryos of a fossil species were
Jump to
found in China, 500 million
Slide #113
years old.
These animals, like their
descendents today,
developed directly from egg
to adult form
Priapulids
 unsegmented, three-part
body plan
 burrow in soft sediments
 capture prey with a toothed,
muscular pharynx that is
everted through mouth
Figure 32.16 Wormlike Marine Ecdysozoans (Part 1)
32.3 What Are the Major Groups of Ecdysozoans?
Kinorhynchs
 Microscopic
 Body has 13 segments, with separate
cuticular plates that are molted
 Live between grains of sand -- meiofauna
 Feed by ingesting sediments through their
retractable proboscis
Eversible proboscis on anterior end
http://science.kennesaw.edu/~jdirnber/InvertZoo/LecNematomorKinPriLor
32.3 What Are the Major Groups of Ecdysozoans?
Loriciferans
also minute
meiofauna
 not discovered until
1983
 Body is covered by
six plates (lorica—
―closet‖)
Figure 32.16 Wormlike Marine Ecdysozoans (Part 2)
32.3 What Are the Major Groups of Ecdysozoans?
Nematomorpha – Horsehair
worms
 very thin
 up to 2 meters in length.
 Most are freshwater
 Larvae are internal
parasites of insects and
crayfish
Larva (left) of Gordius
sp., a parasitic worm of
aquatic insects (right)
http://orion1.paisley.ac.uk/cou
rses/Tatner/biomedia/pictures
http://parasite.org.au/images/parasites/Nematomorpha
32.3 What Are the Major Groups of Ecdysozoans?
 Adult has no mouth and a
reduced gut
 Some may feed only as
larvae;
 others continue to grow
and molt, and may be
absorbing nutrients from
environment
Figure 32.17 A Horsehair Worm
32.3 What Are the Major Groups of Ecdysozoans?
Nematodes (roundworms)
 unsegmented; thick,
multilayered cuticle
 Nematodes shed
cuticle four times
Trichinella spiralis
32.3 What Are the Major Groups of Ecdysozoans?
 Gas and nutrient exchange occurs through
cuticle and gut, which is only one cell thick
 Pharynx, a muscular organ at anterior end,
moves materials through gut
 Move by contracting longitudinal muscles (lacks
circular muscles)  thrashing motion
http://www.microscopy-uk.org.uk/mag/imagsmall/newnematode.jpg
Figure 32.18 Nematodes
32.3 What Are the Major Groups of Ecdysozoans?
 Nematodes are extremely abundant and
universally distributed. About 25,000 species
have been described.
 Many are microscopic; the largest is 9 m
long, a parasite in placentas of female
sperm whales
 Many are scavengers in soil, freshwater,
and marine sediments.
Photo 32.42 Unidentified free-living
marine nematode collected from the
North Sea. LM.
32.3 What Are the Major Groups of Ecdysozoans?
www-biology.ucsd.edu/faculty/images
 Caenorhabitis
elegans is used as
―model organism‖ in
genetics and
developmental
biology research
 Many are predators,
feeding on protists
and other animals
Caenorhabditis elegans, a
common research model
32.3 What Are the Major Groups of Ecdysozoans?
 Many are parasites.
 Parasites of humans cause trichinosis,
filariasis, and elephantiasis.
 Heartworms can parasitize dogs and other
vertebrates
Dog heartworm
(Dirofilaria immitis).
Elephantiasis of the
lower leg, one of the
visible symptoms of
Bancroftian filariasis.
http://www.geocities.com/kandiyohi_bo
xers/health/heartworm.jpg
http://www.neb.com/nebecomm/tech_reference/images/Parasitic_Elephantiasis.jpg
32.3 What Are the Major Groups of Ecdysozoans?
 Life cycles of parasitic
species have special stages
that facilitate transfer to new
hosts
 Trichinella spiralis:
Larvae encyst in animal
muscles, and eaten by humans.
 Emerge in digestive tract,
attach to intestinal walls and
feed.
 Later they bore through
intestinal walls to blood stream,
and form new cysts in muscles

Trichinella spiralis
body plan, and cyst in
host’s muscle tissue
A large mass of Ascaris lumbricoides
that was passed from the intestinal
tract. The worms can measure up to
18 inches long and it is estimated
that 25% of the world's population is
infected with this nematode
http://cache.eb.com/eb/image?id=9847&rendTypeId=4
www.sp01.com/micro/worms/images
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Arthropods and their relatives are
ecdysozoans with limb-like appendages
 Arthropods are dominant animals on Earth
Marrella, called the "lace crab", is most
abundant of all Burgess Shale animals.
www.nmnh.si.edu/paleo/images
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Key features contributing to success of arthropods
 Segmentation
each segment has muscles that operate a
segment and its appendages
 Allows complex movement patterns and
specialization of appendages

Photo 32.77 Family
Mantodae: the California
mantid (Stagmomantis
californica).
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 Rigid exoskeleton
 Made of chitin
 Provides support for walking on land
 Prevents drying out
 Provides some protection against predators
Photo 32.86 Family
Scarabaeidae: tropical
scarab beetle (species
unknown); Costa Rica.
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Arthropods constitute a
monophyletic group
 Gene sequencing
is resulting in new
insights to
evolutionary
relationships within
clade
 Uncertainties
remain in
relationship of
myriapods to other
groups
?
Figure 32.19 The Placement of Myriapods Among Arthropods Is Under Study
?
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Onychophorans and tardigrades are segmented
arthropods with simple, unjointed appendages,
possibly similar to the arthropod ancestor
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Onychophorans (velvet worms)
 live in leaf litter in humid
tropics
 thin, flexible cuticle
 use fluid-filled body cavity as
hydrostatic skeleton for
movement
Figure 32.20 Arthropod Relatives with Unjointed Appendages (A)
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Tardigrades (water bears)
 Use fluid-filled body cavity as a
hydrostatic skeleton
 Extremely small (meiofauna)
 No circulatory or gas exchange
systems.
 Live in marine sands and on
water films on plants
 When water film dries, loose
water and shrink to form a
dormant state that can last at
least a decade
Figure 32.20 Arthropod Relatives with Unjointed Appendages (B)
Arthropods and Their Relatives:
Segmented External Skeletons
Arthropods evolved amazing variety of appendage
forms and functions, including…
 walking and swimming
 gas exchange
 food capture
 copulation for internal fertilization
 sensory perception
http://entnemdept.ufl.edu/bug_club/images/bug_ID/non-insect_arthropods.jpg
Arthropods and Their Relatives:
Segmented External Skeletons
• Similarities in segmentation
patterns among arthropods
arise from actions of
common developmental
genes
 Arthropod body plan is
characterized by a rigid
exoskeleton with jointed
appendages
http://www.ucmp.berkeley.edu/arthropoda/arachnida/tarantula.jpg
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Trilobites
 Flourished in Cambrian
and Ordovician seas, but
went extinct at the end of
Permian
 Left an abundant fossil
record
 Jointed legs first
appeared in trilobites
 Some appendages were
modified for different
functions
Figure 32.21 A Trilobite
Arthropods and Their Relatives:
Segmented External Skeletons
 Exoskeleton made aquatic arthropods excellent
candidates for invading terrestrial environments,
which they did several times
 Four major extant clades:
 Crustaceans
 Hexapods
 Myriapods
 Chelicerates
 Arthropods dominant animals on Earth
 About 1.5 million described species
 Estimated 1018 individuals
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Crustaceans
dominant marine arthropods today
 shrimps, lobsters, crayfishes, and
crabs are decapods
Photo 32.68 Socorro spiny
lobster (Panulirus pencillatus)
Photo 32.69 hermit crab
(Paguristes sp.) with barnacles
32.4 Why Do Arthropods Dominate Earth’s Fauna?
http://pics.davesgarden.com/pics/Magpye_1153951453_503.jpg
 Isopods
 Pill bugs
 Many marine forms,
some parasite
Photo 32.71 Deep-sea isopod
(Bathynomus sp.)
Pillbug, Sowbug, or “roly-poly”
(Armadillidium vulgare)
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 Krill (Euphausids) are abundant
planktonic arthropods, important food
source for many animals, including
baleen whales and penguins
Photo 32.66 Krill
(Euphausia pacifica);
Monterey Canyon, CA.
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 Copepods are also abundant in
plankton
Diaptomus sp.
with eggs
Cyclops, a freshwater copepod with one
eye spot, carrying eggs
http://www.sacsplash.org/cimages/copepod2.jpg
www.microscopy-uk.org.uk/mag/imagsmall/
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Amphipods and ostracods are found in
freshwater and marine waters.
Photo 32.73 Suborder
Hyperiidea: hyperiid
amphipod (Phronima
sp.) with eggs.
Photo 32.60 Tadpole
“shrimp”, an ostracod
(Triops sp.).
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Barnacles are sessile as
adults, resemble bivalve
mollusks, but use
appendages to move
food into the mouth
Barnacle feeding with modified legs
http://www.falklands-underwater.com/invertebrates/images/barnacle.jpg
Photo 32.65 Pelagic
goose barnacles
(Lepas anatifera);
Monterey Bay, CA.
Figure 32.22 Crustacean Diversity (Part 1)
Figure 32.22 Crustacean Diversity (Part 2)
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Most crustaceans have three
body regions: head, thorax,
abdomen.
 Head segments are fused,
and bear five pairs of
appendages
 Thoracic and abdominal
segments usually bear one
pair of appendages each
 Many species have a
carapace – fold of
exoskeleton that extends
over head and thorax region
Figure 32.23 Crustacean Structure
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Appendages on different regions are specialized for
different functions
 Some appendages are branched, with each
branch serving a different function
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Reproduction
 Fertilized eggs are attached to female body in
most species.
 Others release eggs to environment, or attach
them to an object
Spiny Lobster
Female With Eggs
http://www.dnr.state.md.us/fisheries/art2001/spongecrab1.JPG
http://www.cdislands.com/photos_stkitts/stk2/xsk11310.jpg
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Typical larva is nauplius
has three pairs of appendages and one
central eye
 Often develops within egg before hatching

Barnacle nauplius (SEM)
http://www.sci.sdsu.edu/salton
Barnacle nauplius (LM)
www.microscopy-uk.org.uk/mag/imgjan99/
Figure 31.12 Planktonic Larval Forms of Marine Animals (B)
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Insects (hexapods)
 dominant terrestrial arthropods
 inhabit almost every terrestrial and
freshwater environment
32.4 Why Do Arthropods Dominate Earth’s Fauna?
http://www.geology.wisc.edu/~g109/images/Life/L12_Devonian_Life_More_C.jpg
 Molecular data indicate
insect and crustacean
lineages separated about
450 million years ago, about
time of first appearance of
land plants
 Ancestral hexapods
invaded a terrestrial
environment that lacked
any similar organisms
 This, plus wings,
contributed to their
success
http://3dotstudio.com/2wings.jpg
Fossil compound eye of an
insect, from Devonian
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 Homologous genes control development of insect
wings and crustacean appendages
 Insect wing may have evolved from dorsal
branch of a crustacean-like limb
 Probably gill-like structure that had a gasexchange function
Figure 32.28 The Origin of Insect Wings?
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Body has three regions:
 Head – with one
pair of antennae
 Thorax – with three
pairs of legs
 Abdomen – usually
no appendages
Photo 33.40. European
earwig (Forficula auricularia).
Figure 32.24 Structure of an Insect
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Insects have unique gas exchange system:
 air sacs and tubular channels called tracheae
 extend from external openings (spiracles) into
tissues throughout body
www.emc.maricopa.edu/faculty/farabee/BIOBK
www.ipm.uiuc.edu/cropsci270/syllabus/images
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Insects have other unique structures
 External mouthparts (modified appendages) for
tearing, biting, chewing, piercing, sucking
 Diversity of feeding styles allows insects to
be very successful
http://www.arthursclipart.org/biologya/biology/insect%20mouth%20parts.gif
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 Paired antennae with a mechanosensory organ
called Johnston’s organ
 Detects wind, gravity & sound
http://www.nature.com/nature/journal/v458/n7235/fig_tab/458156a_F1.html
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Insects use nearly all species of plants and most
animals as food
 Herbivores can consume massive amounts of plant
material (grasshoppers)
 Many are predators (mantises)
 Others are detritivores that are important in
recycling materials in ecosystems (springtails)
 Some are internal and external parasites of plants
and animals (aphids)
http://www.dkimages.com/discover/previews/
918/25001488.JPG
Praying mantis (Mantis religiosa)
catching a fly
32.4 Why Do Arthropods Dominate Earth’s Fauna?
About 1,000,000 species have
been described – biologists now
believe that may be only small
fraction of actual species
Table 32.2 The Major Insect Groups (Part 1)
Table 32.2 The Major Insect Groups (Part 2)
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Springtails & silverfish are wingless clade of
insects (Apterygotes)
 Probably resemble insect ancestor
 Simple life cycle, and internal mouthparts
 Springtails can be extremely abundant in
soils and leaf litter
Photo 32.74 Silverfish
(Lepisma saccharina).
Springtail
http://mypeoplepc.com/members/arbra/sit
ebuildercontent/sitebuilderpictures
32.4 Why Do Arthropods Dominate Earth’s Fauna?
All other insects are pterygote insects, having two
pairs of wings
 In some groups the wings have been
secondarily lost
 More complex life cycles
Immature stages of pterygote insects do not
resemble adults
 Immature stages between molts called instars

Mating pair, and third
and fourth instars of
monarch butterfly
(Danaus plexippus)
www.mlmp.org/monitoring/Guide/InstarImages
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Metamorphosis: substantial changes that occur
between stages
 Incomplete metamorphosis: changes are
gradual (ex: grasshoppers)
http://cropwatch.unl.edu/photos/cwphoto/
Fourth instars
(above) and
adult male of
migratory
(left) and
differential
(right)
grasshoppers
(not to scale)
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 Complete metamorphosis:
 changes are drastic.
 Ex: Caterpillar changes into butterfly
 wormlike larva transforms itself during
specialized phase called pupa.
Fifth instar to pupa to emergence of monarch (D. plexippus)
http://insects.tamu.edu/images/animalia/arthropoda/insecta/lepidoptera/nymphalidae
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 In many species, different life stages are
specialized for different environments and food
sources
 Often, larvae are adapted for feeding, adults
are adapted for reproduction
Gulf Fritillary [Agraulis
vanillae] larva feeds on
passion vine, while adult
use many other nectar
plants
http://www.jaxshells.org/fritt.jpg
http://www.cirrusimage.com/Lynette/gulf_fritillary_001_thumb.jpg
32.4 Why Do Arthropods Dominate Earth’s Fauna?
http://www.malawicichlidhomepage.com/macro_nature/ladybug.jpg
Pterygote insects were first
animals to fly
 Flight opened up many
new possibilities for
feeding and probably
contributed to their
success
 Adults of most species
have two pairs of wings
 true flies have one pair
 in beetles one pair has
become hardened
Photo 32.88 Predaceous diving
beetle (Dytiscus marginicollis).
Insects: Terrestrial Descendants
of Marine Crustaceans
 Wings apparently arose only once
during insect evolution.
 Winged insects divided into about 29
orders, with three major recognizable
groups:
1.
Those that cannot fold wings back
against body
2.
Those that can fold wings and that
undergo incomplete metamorphosis
3.
Those that can fold wings and that
undergo complete metamorphosis
http://3dotstudio.com/2wings.jpg
32.4 Why Do Arthropods Dominate Earth’s Fauna?
First group – winged insects that cannot fold wings
 Mayflies (Ephemeroptera)
 Adults do not feed, only mate
 Dragonflies and damselflies (Odonata)
 Larvae are aquatic, and many are predators
 Adults are active predators;
Mayflies mating
in June
Dragonfly larvae
http://www.narbeck.org/Bugs/Bug%20Gallery/dragonfly_larva.jpg
Figure 32.27 The Diversity of Winged Insects (Part 1)
32.4 Why Do Arthropods Dominate Earth’s Fauna?
The neopterans are all other pterygote insects that
can fold their wings – two clades.
 The second group has foldable wings with incomplete
metamorphosis, including…
Carolina Mantis Stagmomantis carolina
http://bugguide.net/images/raw
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 Orthoptera
 grasshoppers, crickets, roaches, mantids
Carolina Mantis Stagmomantis carolina
http://bugguide.net/images/raw
Katydid – Scudderia sp.
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 Termites (Isoptera)
Pacific Dampwood Termite Reproductive -Zootermopsis angusticollis
Queen termite with tending
subordinates
http://bugguide.net/images/raw
www.thesahara.fsnet.co.uk/termites
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 Hemiptera (true bugs)
Leaffooted bug, Leptoglossus
phyllopus, nymph on tomato plant
Lygaeus equestris
www.cactus-art.biz/gallery
http://insects.tamu.edu/images/insects/hemiptera
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Aptera and nymphs of soybean
aphids -- Aphis glycine
 Homoptera (aphids,
cicadas, and
leafhoppers)
Seventeen year cicada –
Magicicada septendecim
www.inhs.uiuc.edu/cbd/aphid/images/
www.economist.com/images/20040508
32.4 Why Do Arthropods Dominate Earth’s Fauna?
The third lineage, Holometabolous insects,
have complete metamorphosis
• Lepidoptera (butterflies and moths)
Hummingbird moth – Hemaris thysbe
Luna moth –
Actias luna
http://pinker.wjh.harvard.edu/photos/cape_cod/image
www.etsu.edu/biology/friendso
fnature/images/photogallery
32.4 Why Do Arthropods Dominate Earth’s Fauna?
http://botfly.quiik.com/
 Diptera (flies)
Hawaiian species of Drosophila
Human botfly larva
Botfly – Cuterebra fontinala
www.pbrc.hawaii.edu/microangela/
/www.uoguelph.ca/~samarsha/STEVEweb/images
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 Hymenoptera (sawflies, bees, wasps, ants)
Parasitic wasp laying
eggs on caterpillar
www.mytinygarden.com/images
Ant farming
aphids
Worker Honey Bee Apis mellifera
Wheat stem sawfly –
Cephus cinctus
http://bugguide.net/images
http://entomology.unl.edu/images/smgrains/sawflies
Figure 32.27 The Diversity of Winged Insects (Part 4)
32.4 Why Do Arthropods Dominate Earth’s Fauna?
www.ces.ncsu.edu/depts/ent/clinic/Bugofwk/970081
 Coleoptera (beetles) –
over half of all insects
coleopterans
Dung beetle adult and larva in dung
ball – Deltochilum gibbosum
Nicrophorus orbicollis
http://bugguide.net/images
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Orders Phthiraptera (lice) and Siphonaptera (fleas)
 Most are ectoparasites (external parasites)
 ―Winged‖ insects that do not belong in the above three
lineages
 Derived from flying insects but secondarily lost ability
to fly
 Split from crustacean lineage ~450 mya
Body Louse
(Physconelloides eurysema)
http://medstat.med.utah.edu/kw/derm/mml
Dog flea
(Ctenocephalides
canis)
www.vcbio.science.ru.nl/images
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Myriapods and chelicerates have a body
plan with two regions — head and trunk
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Myriapods (centipedes & millipedes) have a long,
flexible trunk with many pairs of legs
 Centipedes have one pair of legs per segment,
 Millipedes have two pairs — two segments are
fused
Red-headed Centipede
(Scolopendra heros)
North American Millipede
Narceus americana
http://www.bighairyspiders.com/pix/
www.fcps.k12.va.us/StratfordLanding
ES/Ecology/Arthropods
Figure 32.29 Myriapods
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Chelicerates
 Head has two pairs of appendages
modified into mouthparts
 Many have four pairs of walking legs
32.4 Why Do Arthropods Dominate Earth’s Fauna?
 Pycnogonids (sea spiders) — small marine
species
 Horseshoe crabs (Merostomata) have changed
very little over their evolutionary history
Horseshoe Crab (Limulus
polyphemus)
Sea spider (Ammothea verenae)
www.pmel.noaa.gov/vents/nemo/explorer/bio_gallery
www.flaentsoc.org/arthropdiversity/
Figure 32.30 Some Small Groups of Chelicerates
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Arachnids
 Most diverse and abundant chelicerates
 Spiders, scorpions, harvestmen, mites, & ticks
 Most have a simple life cycle

Miniature adults hatch from eggs and begin
independent life
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Spiders are important terrestrial predators
 Some have excellent vision for prey capture
 Others spin elaborate webs to snare prey

―Silk‖ threads produced by modified abdominal
appendages connected to internal glands that secrete
silk proteins
Carolina Wolf Spider (Lycosa
carolinensis) carrying young
Orange-kneed
tarantula
Brachypelma
mesomelas
www.uky.edu/Ag/CritterFiles/casefile/spiders/wolf
32.4 Why Do Arthropods Dominate Earth’s Fauna?
Mites and ticks
 50,000 described species
 Many are parasites of plants and animals
Eyebrow mite
(Demodex
folliculorum)
Deer tick, Ixodes scapularis,
vector for lyme disease
www.polesine.com/pagine/salute/altre
www.dogluvers.com/dog_breeds/upload/thumb
Figure 32.31 Arachnid Diversity (Part 1)
Figure 32.31 Arachnid Diversity (Part 2)
Overview of Protostome Evolution
Protostome species encompass a
staggering number of life forms
• Factors contributing to this
diversity:
 Segmentation – allowed
evolution of rapid movement.
 Complex life cycles –
different stages specialize on
different resources
Photo 32.49 Fossil
water scorpion
Overview of Protostome Evolution
 Diverse feeding
structures – allow species
to take advantage of many
food sources
 Exoskeletons – important
for locomotion; evolved
independently in many
groups
Photo 32.75 Marine
bryozoan (Conopeum
seurati), a lophophorate
Overview of Protostome Evolution
Better locomotion – allowed prey to
escape more easily, but also predators
to capture prey more easily – an
evolutionary “arms race”
Praying mantis feeding
on another insect
http://www.wildeyereptiles.com/catalog/images/DSCN5113.jpg