29/11/2011
Where on the tree?
Ecdysozoa
Protostomes
Lophotrochozoa II:
Molluscs and the lophophorates
Eumetazoa
Deuterostomes
Annelida
Plathelminthes
Rotifera
Chordata
Echinodermata
Ctenophora
Cnidaria
Porifera
Parazoa
Module 11112
Brachiopoda
Mollusca
Radiata
Diploblastic
Animal form and function 1
Velvet worms
Round worms
Lophotrochozoa
Triploblastic
Bilateralia
Tom Hartman
www.tuatara9.co.uk
Arthropods
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Phylum Mollusca
Radula
• Three body parts (some highly modified)
• Coelomate animals
– Mantle : secretes shell (if present) and forms a cavity.
• Paired gill-like structures: outgrowths of mantle
– Visceral mass (gut, heart, kidneys, reproductive organs).
– Muscular foot.
• Most molluscs have a radula to shred food.
• Trochophore larvae (stage maybe reduced to within the
egg).
• Or may develop into a veliger larva.
• Shell may be enormous (snail, oyster, nautilus) or absent
(slug, octopus).
• Various sense organs & complex nervous system.
• Learning, memory and socialization (in a special few).
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Phylum Mollusca
• Decentralised heart.
Largest marine
phylum
Classes
– One or more auricles pump blood to a central
ventricle.
– Octopus hearts maintain a higher blood pressure
than many fish
• A short aorta delivers blood to the coelom and
can act as a hydrostatic skeleton.
• Blood normally contains haemocyanin but
some classes also have haemoglobin.
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Gastropoda
Bivalvia
Polyplacophora
Cephalopoda
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Polyplacophora
• Oval snail like
animal with a shell
divided into 8
plates.
• Head reduced.
• Move on ‘foot’.
• Marine grazers.
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Gastropoda
• Most types undergo
torsion during
development to balance
their visceral mass above
their bodies.
• Brings their gills, anus and
kidneys to rest above their
head = sanitation issues.
• Nudibranchs twist, then
untwist – getting over
their heritage.
Bivalves (lamellibrancha)
clams, oysters, mussels and scallops
• Shells divided into two
halves: left and right.
• When open the ‘foot’ may
extend for anchoring or
digging.
• They use their gills (from
the mantle) for filter
feeding and G/E.
• Scallops can swim by
clapping their shells.
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Cephalopoda
• Closed circulation, main heart and two
‘gill hearts’.
• Highly developed nervous system and
complex brains.
• Jet propulsion through squeezing water
out of mantle cavity (plus waste
evacuation).
• Control of melanophores.
• Communication and learning.
• Octopuses (octopi)
– Control of body shape
– No skeletal elements at all (beak)
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Thaumoctopus mimicus
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Mather J. A. (2008) Cephalopod consciousness: Behavioural evidence.
Consciousness and Cognition 17:37-48
Abstract
Behavioural evidence suggests that cephalopod molluscs may have a form of primary consciousness.
First, the linkage of brain to behaviour seen in lateralization, sleep and through a developmental context
is similar to that of mammals and birds. Second, cephalopods, especially octopuses, are heavily
dependent on learning in response to both visual and tactile cues, and may have domain generality and
form simple concepts. Third, these animals are aware of their position, both within themselves and in
larger space, including having a working memory of foraging areas in the recent past. Thus if using a
‘global workspace’ which evaluates memory input and focuses attention is the criterion, cephalopods
appear to have primary consciousness.
Tool use? Coconut husks.
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Ammonites
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The beak
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Mollusc eyes
Ambergris
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‘Grey amber’
Formed around beaks of giant
squid.
Expelled from stomach of sperm
whales.
Floating in brine under full sunlight
transforms it into a smooth,
compact material with a waxy feel
and a sweet, alluring smell.
Used in the perfume industry.
A 14.8kg lump sold for $295,000.
Exotic perfume is indigestible
lumps of sea monster vomit.
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Lophophore
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Phylum Brachiopoda
Lophophore
Lophophore
Lophophore
Ectoprocts, such as this sea
mat (Membranipora
membranacea), are colonial
lophophorates.
In phoronids such as
Phoronis hippocrepia, the
lophophore and mouth
are at one end of an
elongated trunk.
Brachiopods have a hinged shell.
The two parts of the shell are
dorsal and ventral.
• Look like a bivalve
mollusc.
• Large complex
lophophore.
• Shells are dorsal and
ventral.
• Remnant (330spp) of a
vast assemblage of fossil
species that nearly
ended at the end of the
Cretaceous period.
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Ships that pass in the night.
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Ships that pass in the night.
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29/11/2011
Where on the tree?
Ecdysozoa
Protostomes
Velvet worms
Round worms
Lophotrochozoa
Protostomes
Brachiopoda
Mollusca
Triploblastic
Bilateralia
Eumetazoa
Ecdysozoa
Arthropods
Deuterostomes
Eumetazoa
Annelida
Plathelminthes
Rotifera
Chordata
Echinodermata
Ctenophora
Ctenophora
Parazoa
Brachiopoda
Mollusca
Deuterostomes
Starfish, urchins, etc.
Radiata
Diploblastic
Velvet worms
Round worms
Lophotrochozoa
Triploblastic
Bilateralia
Segmented worms
Plathelminthes
Rotifera
Lanclets, vertebrates, etc.
Arthropods
Radiata
Diploblastic
Cnidaria
Porifera
Parazoa
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Cnidaria
Porifera
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Ecdysozoa
Shedding an exoskeleton
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