On CephalopodsBy Claire and Asparaguy

Can you identify these cephalopods? :D

What is a cephalopod? 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.

1 2 3

4 5

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

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.

Image from Clarkson

Simplified evolution of the extant cephalopods!

Arms Beak Hyponome Digestive tract Gills Internalised shell Mantle

Tentacles Shell Gills Siphuncle

Septum Umbilicus Camerae

Hyponome

Tentacle Stomach Caecum Heart

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.

Overview of the cephalopods

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=omXS1bjYLMI

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.

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.

The cephalopod circulatory system

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 pigment-containing 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 light

Hunting prey – light becomes polarised when reflected off fish scales

Covert communication using patterns of polarised light on their skin

Photoreceptors in a cephalopod eye

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.