Class Cephalopoda~700 species, all marine

Subclass Nautiloidea mostly extinct- only 7 living species

Subclass Coleoidea nearly all living cephalopods

Superorder Decapodiformes (cuttlefish, squids)Superorder Octopodiformes (octopus, argonauts)

Subclass Ammonoidea extinct, but formerly diverse group

Class Cephalopoda

jet propulsion- opening to mantle cavity is modified into hyponome (ventral funnel or siphon) that can direct water expelled from the mantle cavity.

Foot modified into arms and/or tentacles, which in one subclass (Coleoidea) usually bear suckers.

Radula plus beak, venom glands

Closed circulatory system

Highly developed sensory, locomotory, and behavioral abilities. Intelligence?

Among the largest invertebrates- giant squid exceeds 20 meters (including the tentacles)

Phylum Mollusca

Class Cephalopoda

Subclass Nautiloidea Nautilus

Subclass Ammonoidea ammonites- all extinct

Subclass Coleoidea Order Sepioidea cuttlefishes Order Teuthioidea squids Order Octopoda octopods Order Belemnoidea belemnoids- all extinct

Class CephalopodaSubclass Nautiloidea

Characters

1. Chambered shell used for protection and buoyancy.

2. 2 pairs of gills (tetrabranchiate)

3. Arms are adhesive (no suckers)

4. Eyes form images via a pin-hole opening.

5. Funnel formed by overlapping flaps.

6. Only ~6 living species- deep water in Indo-Pacific region

7. Many extinct forms- known from the Cambrian, but radiated in the Ordovician

siphuncleWater content of the chambers is adjusted by siphuncle to control buoyancy

Nautilus as design iconJules Verne 1870 “20,000 Leagues Under the Sea”

Nautilus as design iconNautilus exercise equipment uses a log spiral cam

Nautilus habits

• Generalized predator/scavengers

• tropical waters where slopes of coral reefs descend into deep waters.

• Daily vertical movements up to 1500 feet- ascending at night to feed.

• http://www.youtube.com/watch?v=QMFqV4SJLWg

Ammonites- (Subclass Ammonoidea)

Very diverse, but all extinct.

Appear in Devonian.

Evolved rapidly (especially in the Mesozoic) and are therefore good stratigraphic markers.

Baculites fossil & reconstructions

Baculites-Ammonite cephalopods with straight or curved conical shells, complex sutures dividing chambers

Ammonites, Reconstructed

Ammonites, a group of cephalopods with external shells that went extinct roughly 65 million years ago, were among the most abundant marine invertebrates in Earth's history. Their position in the food web is not well understood.

In the 1-7-11 issue of Science, researchers used 3D X-ray tomography to reconstruct the mouthparts of fossil specimens of the ammonite Baculites

(http://video.sciencemag.org/VideoLab/736437601001/1). The researchers postulate that these ammonites likely fed on plankton and note that ammonites went extinct at the end of the Cretaceous, as there was an abrupt decline in several groups of plankton around the same time period.

Another possibility is that larval ammonites were planktonic and were affected by whatever knocked down planktonic organisms at that time

Class Cephalopoda Subclass Coleoidea

Cuttlefish, squids, octopus, argonauts, belemnites

Basic anatomy

Single pair of ctenidia(dibranchiate)

8-10 arms with suckers (octopods have 8, cuttlefishes & squids have 10)

Shell is reduced and internal, or missing altogether

More detailed anatomy (squid)

The cephalopod eye (squid or octopus, for example) is remarkably convergent on the “camera” eye design of vertebrates

lens

iris

Optic nerve

retina

Coleoid arms & tentacles have suckers, and sometimes hooks

Chromatophores

• Organs that control color at body surface.

• Elastic saccule containing pigment granules

• 15-25 radial muscles surround the sacculus. When these contract, they expand the sacculus and make the coloured pigment granules visible.

• Direct connections to nervous system

• http://www.youtube.com/watch?v=2x-8v1mxpR0

Class Cephalopoda

Subclass Coleoidea

Cuttlefish (order Sepioidea)

eight arms, two tentacles

What kind of similarity is this?

Anomalocaris from Burgess Shale, 500 mya

Sepia apama

southern, eastern Australiaup to 1 m long

http://www.arkive.org/giant-cuttlefish/sepia-apama/video-00.html

Cultural uses of cuttlebone

As mineral supplementAs casting material for jewelry

The shell of cuttlefish is internal, porous, has buoyancy function

Belemnoids- extinct order of coleoids. Internal, cone-shaped shell, arms bore hooks. Appeared in the Jurassic and depart in the Eocene. Jurassic and Cretaceous were peak.

Squids- Order Teuthoidea

• Commercial importance- harvested for food- 200 million tons annually(mmmm. calimari!)

• Ecological competitors of teleost fishes…fast, mobile pelagic predators.

• Ink gland, pen

Class Cephalopoda

Subclass Coleoidea Squids (Order Teuthoidea) eight arms (short) , two tentacles (long)

Octopods- Order Octopoda

• Most specialized for benthic habitat but some are pelagic (nearly all squids are pelagic)

• Mainly crevice and hole-dwellers

• Shell is absent, tentacles are absent, leaving eight arms.

Class Cephalopoda

Subclass Coleoidea

Octopods(order Octopoda)

Nouryi's Argonaut

Argonauta nouryi Lorois, 1852

Blue-ringed octopus- Hapalochlaena maculosa

small (100 g and 20 cm across spread tentacles)

Japan to Australia in shallow tropical water and in tide pools

tetrodotoxin