Topic 8 Lophotrochozoan "Minor" Phyla

Lophotrochozoa “Minor Phyla”
Eutrochozoa: Rotifera, Acanthocephala,
Entoprocta,Platyhelminthes, Nemertea, Mollusca,
Sipuncula, Annelida
Lophotrochozoa
Lophophorata: Ectoprocta, Brachiopoda,
Protostomia
Phoronida
Ecdysozoa: Onychophora, Tardigrada,
Arthropoda, Nematoda, Nematomorpha,
Kinorhyncha, Loricifera, Priapulida
Cuticulata
Gastrotricha
Parenchymia
Platyhelminthes
Nemertea
Annelida
Mollusca
Sipuncula
Entoprocta
Rotifera
Lophotrochozoa
Acanthocephala
Ectoprocta
Lophophorata
Brachiopoda
Phoronida
Phylum Sipuncula
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The Phylum Sipuncula (from Latin: meaning
“little pipe”) consists of approximately 250
species of benthic, marine wormlike animals,
most from 15-30 cm in length (range 2mm to
70cm).
Sipunculids produce a trochophore larva similar
in structure to that of the annelids.
Phylum Sipuncula

Sometimes referred to as the “peanut
worms” (probably for the gridlike pattern
on their epidermis) most sipunculids
burrow in sand or silt or occupy crevices
or empty mollusc shells or worm tubes
http://www.glaucus.org.uk/Sipunculus-nudus-RL.jpg
Sipunculid clip
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One minute clip of sipunculid
http://www.youtube.com/watch?v=S1zQC
a5cfcQ
Phylum Sipuncula
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The body is unsegmented and divided into an
anterior introvert and a posterior trunk.
The introvert is a retractile structure at the
anterior end of the animal and can be half the
body length.
Sipunculids have a fluid filled coelom and a
hydrostatic skeleton. The pressure of the fluid
in the coelom is used to extend the introvert.
http://www.eol.org/pages/887
1
Phylum Sipuncula
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Sipunculids are generally non-selective
deposit feeders and they use the ciliated
tentacles or lobes surrounding the tip of
the introvert to collect food.
They eat a variety of small easy to acquire
food items: algae, unicellular organisms,
larvae and detritus
Phylum Sipuncula
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The introvert is also used to burrowing
into sediments.
Coelomic pressure is used to extend the
introvert into the sediment and anchor it
in place. Retractor muscles then contract
pulling the introvert forward and drawing
the rest of the animal forward.
Sipunculid clip
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
Sipunculid burying itself one minute
http://www.youtube.com/watch?v=aq6kE
X9igeI
Parenchymia
Platyhelminthes
Nemertea
Annelida
Mollusca
Sipuncula
Entoprocta
Rotifera
Lophotrochozoa
Acanthocephala
Ectoprocta
Lophophorata
Brachiopoda
Phoronida
Phylum Entoprocta
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
AKA the kamptozoans or the “goblet
worms”, entoprocts are small (1cm),
sessile marine animals most of which are
colonial.
The body, which is covered by a thin
external cuticle consists of a long mobile
contractile stalk topped by a calyx, which
contains the organs and a crown of
tentacles.
http://www.biocyclopedia.com/index/gener
al_zoology/phylum_entoprocta.php
Phylum Entoprocta
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Entoproct means “anus inside” and this
refers to the fact that the mouth and the
anus are surrounded by the ring of
tentacles.
The tentacles are solid and non rectracile,
Instead they can be rolled up and covered
by the intertentacular membrane.
Phylum Entoprocta
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
Entoprocts occur in shallow water and
feed on suspended particles that they trap
using mucus covered cilia on their
tentacles.
The food is directed down the tentacles to
the mouth.
Phylum Entoprocta


Reproduction occurs either asexually by
budding or sexually (they are
hermaphroditic).
Fertilized eggs are incubated in a pouch
within the calyx and the embryos are fed
by parental cells. The embryo develops
into a free-swimming trochophore larva
that settles and metamorphoses into the
adult form.
Parenchymia
Platyhelminthes
Nemertea
Annelida
Mollusca
Sipuncula
Entoprocta
Rotifera
Lophotrochozoa
Acanthocephala
Ectoprocta
Lophophorata
Brachiopoda
Phoronida
Phylum Rotifera
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
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Rotifers are named for their characteristic
ciliated crown or corona, which when it beats
looks like a rotating wheel.
Rotifers are tiny animals (most are 100-300µm
long and the largest only 3mm long) the
majority of which live in freshwater and are
benthic inhabitants (live on the bottom).
About 2000 species have been described.
Figure 15.18
9.1
Phylum Rotifera
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The beating of the cilia in the corona draws in
plankton-containing water for food.
The mouth opens to a modified muscular
pharynx known as a mastax, which is a
structure unique to rotifers.
The mastax has a set of complex jaws, which
are used to grasp and chew food.


Rotifer video 1 minute
http://www.youtube.com/watch?v=cYNJO
VDQexA
Phylum Rotifera
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
One group of rotifers, the Bdelloid rotifers,
are very unusual in that there are no
males, hermaphrodites, or evidence of
meiosis.
Molecular evidence suggests that there
has been only asexual reproduction in this
group for several million years.
http://www.arcodiv.org/seaice/rotifers/Antarctic_rotifer_Philodina_gregaria_400x300.jpg
Phylum Rotifera


Because of the problem of accumulation of
deleterious mutations in lineages of exclusively
asexually reproducing animals (a process known
as Muller’s ratchet) it is unclear how the
bdelloids have been able to dispense with sexual
reproduction entirely.
Other rotifers reproduce using a combination of
sexual and asexual reproduction.
Parenchymia
Platyhelminthes
Nemertea
Annelida
Mollusca
Sipuncula
Entoprocta
Rotifera
Lophotrochozoa
Acanthocephala
Ectoprocta
Lophophorata
Brachiopoda
Phoronida
Phylum Acanthocephala


Acanthocephalans are commonly known
as spiny-headed worms because of the
spiny eversible proboscis they use to
attach to the gut of their host.
All 1100 species of Acanthocephalan are
endoparasitic and most parasitize fish,
birds and mammals. Most small 1mm to 34cm a few up to 1m long.
http://rydberg.biology.colostate.edu/Dissections/acanthocephala/acanthfemmal.jpg
Phylum Acanthocephala







Bilaterally symmetrical
No gut
Body unsegmented
Prominent spiny proboscis
Body cavity is a pseudocoelom (mesoderm lines
only outer edges of blastocoel, body cavity not
lined with peritoneum).
No respiratory or circulatory system
Simple nervous system single anterior ganglion
with connecting nerves to organs.
Figure 15.20
9.3
http://upload.wikimedia.org/wikipedia/commons/9/99/Acanthocephala_Rhadinorhynchu
s.jpg
Acanthocephalan proboscis
Phylum Acanthocephala


Body wall covered with numerous minute
depressions which increase the surface
area of tegument and facilitate (as in
cestodes) absorption of food from host’s
gut.
As in cestodes, Acanthocephalans lack a
gut.
Phylum Acanthocephala
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
Acanthocephalans have a lifecycle in
which a vertebrate is the definitive host
(in alimentary canal) and an invertebrate
the intermediate host.
Acanthocephalans, as other parasites do,
modify the behavior of the intermediate
host to enhance the chances of its being
eaten.
Phylum Acanthocephala


For example, acanthocephalans that parasitize
Gammarus, a small freshwater crustacean,
cause the Gammarus to alter its behavior in the
presence of ducks, a common predator.
Instead of diving to the bottom when a duck
appears, the Gammarus swims into the light and
grasps tightly onto a piece of vegetation, greatly
increasing its chances of being eaten.
Phylum Acanthocephala


The change in behavior appears to be caused by
the Acanthocephalan pumping a serotoninboosting molecule into the Gammarus’ brain.
This causes the Gammarus to think it’s having
sex and cling as it would if mating. Interestingly,
the parasite’s manipulation also causes female
Gammarus to mimic the males mating behavior.
Phylum Acanthocephala



Another Acanthocephalan that parasitizes pill
bugs causes them to reverse their normal
behavior and avoid humid, dark areas.
Instead they wander in the open where they are
much more vulnerable to birds, the
acanthocephalans definitive host.
The parasite’s manipulations are very effective.
Although fewer than 1% of pill bugs are typically
infected with acanthocephalan parasites, 30% of
pill bugs delivered to nestlings are infected.
Parenchymia
Platyhelminthes
Nemertea
Annelida
Mollusca
Sipuncula
Entoprocta
Rotifera
Lophotrochozoa
Acanthocephala
Ectoprocta
Lophophorata
Brachiopoda
Phoronida
Phylum Ectoprocta


Also known as the bryozoans or moss
animals they are small (<0.5mm) colonial
animals, but colonies can be up to 1 meter
across (although most are 10cm or so)
Most are marine and form masses on
rocks and other substrates where they
feed on phytoplankton and other small
organisms which they catch using cilia on
their lophophore.
Lophopodella carteri
lophophore
http://www.bio.umass.edu/biology/conn.river/bryozoa.html
Phylum Ectoprocta



Individual zooids are genetically identical.
The zooids are connected to each other
and surrounded by a protective calyx as in
entoprocts.
Most zooids are feeding zooids called
autozooids. These use the lophophore to
feed. The tentacles are extended by
hydrostatic pressure and prey is trapped
using cilia
Phylum Ectoprocta


The lophophore and mouth are mounted
on a tube called an invert that can be
everted through an opening in the calyx
and rapidly withdrawn if threatened.
The mouth is found within the ring of
tentacles but the anus is outside the ring
(in contrast to entoprocts).
Phylum Ectoprocta

Other types of zooids include spinozooids
which possess protective spines,
gonozooids, which act as brood chambers
for developing eggs and modified
autozooids called avicularia which use a
modified operculum to snap at threatening
organisms.
www.marlin.ac.uk
Phylum Ectoprocta
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
Colonies of ectoprocts in freshwater
temperate habitats die in the fall, but
leave behind statoblasts, which are groups
of cells surrounded by a protective
envelope.
Zooids emerge in the spring and a new
colony forms by budding.
Phylum Ectoprocta
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
Ectoprocts have a rich fossil record and
over 15,000 fossil species have been
described.
Fossils are known from as far back as the
Cambrian period (500mya).
Phylum Ectoprocta


Ectoproct video 1 minute
http://www.youtube.com/watch?v=tpifpqr
QKRA
Parenchymia
Platyhelminthes
Nemertea
Annelida
Mollusca
Sipuncula
Entoprocta
Rotifera
Lophotrochozoa
Acanthocephala
Ectoprocta
Lophophorata
Brachiopoda
Phoronida
Phylum Brachiopoda



Greek: brachion: branch; pous: foot.
The living brachiopods are the remnants
of a once much more diverse group.
There are about 335 living species vs >
26,000 fossil species.
Superficially similar in lifestyle and
external appearance to bivalve molluscs.
http://paleo.cortland.edu/tutorial/Brachiopods/Brachiopod%20Images/lingula.GIF
Brachiopod characteristics

The body is enclosed within a symmetrical
bivalve shell as is the case in molluscs.
However, unlike molluscs brahiopods have
a dorsoventrally oriented shell with two
unequally sized valves unlike molluscs
which have left and right valves.
Phylum Brachiopoda


Brachipods possess a stalk or pedicle (130cm in length), which is typically
attached to rock or anchored in sediment
A large, anterior mantle cavity contains
the lophophore which is used for
suspension feeding.
Brachipod cross section: http://aalliiffaazzeellii.googlepages.com/pra1.gif
Principal organs of a brachiopod as typified by Terebratulina. (After R. C. Moore, ed.,
Treatise on Invertebrate Paleontology, pt. H, Geological Society of America, Inc., and
University of Kansas Press, 1965)
Phylum Brachiopoda

The lophophore occupies much of the
internal space of the brachipod and has a
branched rather than circular structure
(hence the name as brach means a
branch) with complex folding of the
lophophore being common.
http://rydberg.biology.colostate.edu/Dissections/terint.htm
Phylum Brachiopoda

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Brachipods are entirely marine and most
occur in areas without strong waves or
currents.
They occur at depths ranging from the
intertidal to the deep sea.
Parenchymia
Platyhelminthes
Nemertea
Annelida
Mollusca
Sipuncula
Entoprocta
Rotifera
Lophotrochozoa
Acanthocephala
Ectoprocta
Lophophorata
Brachiopoda
Phoronida
Phylum Phoronida


Sometimes called horseshoe worms they
build tubes of chitin and filter feed using a
lophophore.
The are marine and occur in sediments
between the intertidal and about 400m
depth.
Phylum Phoronida


Most phoronids range in length from 220cm, but can reach 50 cm.
They secrete a tube of chitin and the
lower end of the animal is swollen into an
ampulla, which anchors the animal and
allows it to quickly retract its lophophore
into the tube.
Phylum Phoronida

Phoronids can be extremely abundant
numbering thousands of individuals per
sq. meter. They are unpalatable to many
predators and that likely explains the high
densities.
Phylum Phoronida

Phoronids feed on a variety of small
filterable prey including algae, small
invertebrates and flagellates which are
caught using the lophophore.
Phylum Phoronida


Some species are hermaphroditic and the
rest dioecious. Eggs are in many species
brooded for a while before being released
into the water.
Most species develop free-swimming
larvae that feed on plankton that they
catch using tentacles.
Phoronid larva (they are called actinotrochs
http://en.wikipedia.org/wiki/File:Phoronid_ASlotwinski.jpg
Phylum Phoronida

After a larval period of about 20 days the
larva settles on the bottom and in about
30 minutes undergoes a rapid
metamorphosis in which the larval hood
and tentacles are reabsorbed, the adult
lophophore is formed and the gut forms a
u-bend with the anus opening outside the
tentacles.
Phylum Phoronida

There are only a dozen described species,
but this is certainly an underestimate as
more than 25 larval forms have been
described.
Phylum Phoronida

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Phoronid worm (1 minute)
http://www.youtube.com/watch?v=jZ1bibYY1w
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