Download On Cephalopods - WordPress.com

On Cephalopods
By Claire and Asparaguy
What is a cephalopod?
1
2
3
1: Pfeffer’s Flamboyant
Cuttlefish (Metasepia
pfefferi)
2: Bigfin Reef Squid
(Sepioteuthis lessoniana)
3: Greater Blue-Ringed
Octopus (Hapalochlaena
lunulata)
4: Shells of various
species of nautiloids
(Nautilus macromphalus,
Allonautilus scrobiculatus,
and Nautilus pompilius)
5: The Dumbo Octopus,
Grimpoteuthis.
4
Can you identify these cephalopods? :D
5
Overview of the cephalopods
 A cephalopod is a member of the class
Cephalopoda (phylum Mollusca)




Bilateral body symmetry
Prominent head
Set of tentacles or arms (number and type varies)
Ability to squirt ink
 Cephalopod is Greek for “head-footed”
 Two subclasses (Coleoidea and Nautiloidea)
Overview of the cephalopods
 The most intelligent invertebrates
 Most have well-developed eyes
 All cephalopods are active predators
 Move by jet-propulsion – expelling water at high
speed through a hyponome.
 Most possess an ink sac which produces brown
or purplish ink that is used to ward off attackers.
Septum Umbilicus Camerae
Simplified evolution of the
extant cephalopods!
Hyponome
Image from Clarkson
Tentacle Stomach Caecum
Heart
Tentacles Shell Gills Siphuncle
Arms Beak Hyponome Digestive tract Gills Internalised shell Mantle
Overview of the cephalopods
 The ink of cephalopods:



When combined with less mucus, simply acts as a
smokescreen to interfere visually with the predator
The ink’s tyrosinase may also irritate or inactivate
the chemosensory systems of the predator.
When combined with large amounts of mucus, it
forms a pseudomorph.
Overview of the cephalopods
 The beak of cephalopods:



Chitinous structures shaped like a parrot’s beak
Formed by the gradual hardening of tissues
Muscle around the beak is known as the buccal
mass; also contains radula (a rough tongue)
Overview of the cephalopods
 Shells of the cephalopods:




Nautiluses retain an aragonitic external shell.
Squids have the squid pen or gladius.
Cuttlefish have a porous, aragonitic cuttlebone.
The shell is completely absent in most octopuses.
Overview of the cephalopods
 Cephalopod locomotion:




Squids move by drawing water into their mantle
cavities and expelling it through their funnels.
Octopuses use the suckers on their arms to move
about on the seafloor.
Cuttlefish undulates the fin fringe running along
their mantles in addition to jet-propulsion (gas filled
cuttlebone provides buoyancy)
Some squids, such as Ommastrephes bartramii,
the neon flying squid, can “fly”!
Overview of the cephalopods
 Cephalopod locomotion:





The mantle is made of longitudinal and circular muscle fibres.
The circular muscles relax, expanding the mantle cavity.
The circular muscles then contract, sealing the opening.
The longitudinal muscles contract and expel the water.
http://www.biology.ualberta.ca/courses.hp/zool250/
animations/Squid.swf
Overview of the cephalopods
 Squids such as the neon
flying squid, or even the
“jumbo” squid (Humboldt
squid) can propel
themselves out of the water
and stabilise their flight with
their fins.
The cephalopod nervous system
 Cephalopods (esp. coleoids) are known to be
the most intelligent invertebrates.



Spatial learning capacity
Navigational abilities
Predatory techniques
 Nervous system affects chromatophores
The cephalopod nervous system
 The squid giant axon:






Up to 1 mm thick
Unmyelinated, unlike in vertebrates
Branches out from the stellate ganglion
Innervates the mantle of the squid
Responsible for mantle contractions – thus, forcing
water through the hyponome.
http://www.youtube.com/watch?v=omXS1bjY
LMI
The cephalopod nervous system
 The squid giant synapse:





Largest chemical junction in nature
Identified by J. Z. Young in 1939
Lies in the stellate ganglion
A chain of three neurons
Relays input from cephalic ganglion (the squid’s
brain) to the mantle.
The cephalopod nervous system
The cephalopod nervous system
The cephalopod circulatory system
 A closed circulatory system
 Relies on haemocyanin rather than
haemoglobin to transport oxygen

Colourless blood turns blue when exposed to air
 Coleoids (squids, cuttlefish and octopuses)
have two branchial hearts (also known as gill
hearts) and one systemic heart which pumps
blood around the body.
The cephalopod circulatory system
 Note copper prosthetic groups
coordinated by histidine residues.
 In environments with low
temperature and low oxygen
pressure, haemocyanin is more
efficient than haemoglobin.
 Haemocyanin is not bound to red
blood cells, but rather are suspended
in the haemolymph.
Chromatophores
 Soft-bodied cephalopods rely heavily on
camouflage to escape detection by predators
 Colour patterns of cephalopods are largely
controlled by chromatophores in the dermis
 Each chromatophore is a
miniature organ consisting of a
single pigment-filled saccule
and numerous muscle, nerve,
glial and sheath cells
Chromatophores
Chromatophores
 Melanin pigments are yellow, orange, red or
brown
 Saccules darken with age, presumably due to
increased zinc content
 When attached muscles contract, the pigmentcontaining saccule will stretch to cover a larger
area, displaying the pigment
 Relaxation of muscles causes the saccule to
shrink, hiding the pigment
Chromatophores
 Each chromatophore is directly controlled by the
brain (via associated neurons), enabling:
 Generation of complex patterns
 Extremely rapid response to stimuli
The cephalopod eye
 Most sophisticated of all invertebrate eyes
 As complex as and structurally similar
vertebrate eyes (single-lens), but not
homologous
 During organogenesis, the vertebrate eye
develops as an extension of the brain
 The cephalopod eye develops from the head
surface
The cephalopod eye
Vertebrate (human) eye
Cephalopod (octopus) eye
The cephalopod eye
 Able to detect polarised
Photoreceptors in a
cephalopod eye
light
 Hunting prey – light
becomes polarised when
reflected off fish scales
 Covert communication
using patterns of
polarised light on their
skin
The cephalopod eye
Octopus
Squid
Cuttlefish
Nautilus
The squid and the cuttlefish
 What are the differences?




The squid is of the order Teuthida; the cuttlefish is
of the order Sepiida.
The squid is torpedo-shaped; the cuttlefish is
broader and more flattened.
The squid has a chitinous squid pen; the cuttlefish
has a porous cuttlebone.
The squid moves much more swiftly than the
cuttlefish, which relies more on camouflage.
The squid and the cuttlefish
 Interesting squid facts:
 Deep water squid have the second greatest known
penis length relative to body size
 The squid systemic heart has 3 chambers.
 Squid ink is used in making Arròs negre.
 Some male squids can detach an arm and use it to
transfer sperm to the female.
The squid and the cuttlefish
 Interesting cuttlefish facts:
 All cuttlefish contain neurotoxins.
 Cuttlefish have some of the largest brain-to-body
size ratios.
 The colour name sepia comes from the Greek and
Latin word for “cuttlefish”.
 Lateral lines allow it to detect sound – it can hunt
with 50% accuracy in total darkness
 The Pfeffer’s Flamboyant Cuttlefish is as toxic in
its muscles as the Blue-Ringed Octopus.
The squid and the cuttlefish
 Interesting squids:
 Colossal Squid (Mesonychoteuthis hamiltoni)
 Crachiid Squid (family Cranchiidae)
 Cock-eyed Squid (family Histioteuthidae)
 Promachoteuthis sulcus
 Piglet Squid (Helicocranchia sp.)
 Firefly Squid (Watasenia scintillans)
The squid and the cuttlefish
The bobtail squid
 Closely related to cuttlefish
 Rounded mantle and no cuttlebone
 Symbiotic relationship with bioluminescent
bacteria, Vibrio fischeri.
 Certain species bury themselves in sand.
 http://www.youtube.com/watch?v=eB-M4adJIeY
The octopus
 Interesting octopus facts:
 Chemoreceptors on suction cups allow them
to taste what they are moving across
 Most are semelparous and exhibit unnatural,
non-coordinated behaviour (senescence)
after mating, eventually starving to death
 This is controlled by endocrine secretions
from the optic glands
The octopus
 Interesting octopuses:
 Blanket Octopus (Tremoctopus spp.)
 Vulcanoctopus hydrothermali
 Paper Nautilus (Argonauta spp.)
 Mimic Octopus (Thaumoctopus mimicus)
The nautilus
 Interesting facts about nautiluses:
 Two pairs of gills; thus called tetrabranchs.
 Shell is an example of logarithmic spiral.
 Considered living fossils
 Radula have nine teeth.
 The osmena pearl is derived from the shells.
 Lifespan of up to twenty years.
The nautilus
Thank you!! :DDD
Um.