Class Cephalopodathe squids, octopus, nautilus, and cuttlefish

Richard E. Young, Michael Vecchione and Katharina M. Mangold

Class Cephalopoda• shell is present, reduced, or lost• all are predacious with beak-like jaws• highly developed head and sensory organs (very intelligent)• closed circulatory system• swim via jet propulsion• foot is lobed and forms tentacles• direct development (no larvae)

Class Cephalopoda

• male transfers a spermatophore to female using a special pair of tentacles • female seals herself up in a den to lay eggs which she attaches to the top of the den• she cares for these eggs (in some species up to 6.5months) • after the eggs hatch she usually dies

Reproduction

Class Cephalopoda

Nautilus:• have a chambered shell that aids in maintaining buoyancy• chambers are filled with gas

siphuncle(cord of tissue connected to visceral mass)

chambers

Ammonoids

Class Cephalopoda

Squids:• have a reduced, internal shell called the pen

Cuttlefish:• have a reduced, internal shell called a cuttlefish bone

Spirula sp.

Reduced Internal Shell

Cephalopods have elaborate mating displays including complex courtship displays.

Bioluminescence

Class Cephalopoda

• Architeuthis sp. the largest giant squid found to date have been 18 meters in length • they live in the deep sea• sperm whales (~20m in length) are their major predators

Robust clubhook squid Moroteuthis robusta (Cephalopoda: Onychoteuthidae) in Puget Sound (Washington State, USA)

Robust clubhook squid Moroteuthis robusta

Jumbo Flying Squid Dosidicus gigas

Calamary

Class Cephalopoda

Octopus:• have lost the shell completely• most intelligent invertebrate

Giant Pacific OctopusOctopus dofleini

• This species is one of the largest known octopods; the heaviest on record weighed nearly 600 pounds. It is fished commercially from Alaska to northern California. The Giant Pacific Octopus feeds on shrimps, crabs, scallops, abalones, clams, various fishes, and smaller octopods. It in turn is eaten by seals, sea otters, sharks, and other large predators.

Giant Pacific OctopusOctopus dofleini

• Deadly venom and warning coloration

• The Blue-ring Octopus Hapalochlaena maculosa

• It kills prey by delivering a poison in the saliva. The poison is a neurotoxin (maculotoxin) that is strong enough to kill a human being.

The recently discovered mimic octopus (Octopus horridus) is, according to some sources, the coral reef’s great pretender. Some people have filmed, photographed and observed this octopus mimicing a great range of species including flatfish, seasnakes, jawfish, mantis shrimps, lionfish and others.

Argonauta nodosaThe paper nautilus

• The paper nautiluses, Argonauta sp., are not nautiluses at all, they are octopuses! The paper thin white calcareous 'shell' is actually an egg case made by females.

Argonauta nodosaThe paper nautilus

• Argoanuts are open-ocean cephalopods.

• In addition to small crustaceans, they ingest jellyfish!

Argonauta nodosaThe paper nautilus

• The most sexually dimorphic cephalopods.

• The females are considerably bigger the males. Females are thought to live longer and reproduce many times while the tiny males are thought to only reproduce once and have much shorter life spans.

• During mating, one of the male's arms breaks off inside the mantle of the female. So both size and life span are radically different between the sexes.

Class Polyplacophorathe “Chitons”

Class Polyplacophora

• have 8 rows of articulating plates• use radula to graze algae on substrate• mantle forms a girdle around plate edge• no veliger larvae

girdle

plates

Cryptochiton sp.

• The Gumboot ChitonThe gumboot chiton is one species of chiton that is a little different from the rest; it is the largest species of chiton in the world, growing up to 30 cm in length - and its eight plates are covered up by thick, leathery, brick-red flesh.

Cryptochiton sp.

Class Monoplacophora

In 1952 ten living specimens of Neopilina were dredged from the deep ocean trench off the Pacific cost of Costa Rica.

3 mm-3 cm in size.

Repetition of parts.

Class Aplacophora

Class Aplacophora

• Strange small worm like molluscs.

• Less than 5 mm.

• Head is poorly developed and shell is absent.

• Cuticle contains calcareous scales or spicules.

Class Scaphopodathe “tusk shells”

Class Scaphopoda

located above sand

located below sand

feeding tentacles

• shell is modified into hollow tube that is open at both ends • the mantle wraps completely around the visceral mass• sessile and feed in sediment during reproduction produce trochophore larvae

Class Bivalvia(class Pelecypoda)

the “bivalves”

Class Bivalvia• clams, mussels, oysters, scallops • use gills for respiration and filter feeding • shell is modified into a bivalved shell connected by muscles and ligaments• no head (reduced sensory organs), no radula• foot can be modified for digging

dorsal

anterior

posterior

ventral

umbo-the oldest part of the shell

ridges show where mantle has laid down shell

Introduction to Bivalves

• Mollusks in the class Bivalvia originated in, and many have remained in the world oceans.

• Some have succeeded in colonizing fresh water habitats, and have radiated in species diversity.

• Bivalves as adults are an important part of the benthic infauna with restricted movement on and through the substrate.

Bivalve Anatomy

Cilia are used for filter feeding

A LARGE UNIONID FILTER FEEDING

Scolenidae and Cultellidae: Razor Shells and Jackknife Clams

The Geoduck Panopea generosa a giant Californian bivalve, the body and siphon of

which cannot be enclosed within valves

Boring Bivalves (Shipworms: Teredinidae)

Boring Bivalves

Boring Bivalves

Boring Bivalves

Boring Bivalves

Pen Shell Atrina rigida

Attached surface dwellers (Epifauna)

Pen Shell Atrina rigida

They utilize byssal threads which are believed to represent a persistent

larval adaptation

Mussels (Mytilus sp.)

Bassal threads

The Giant Clam Tridacna sp.

The Giant Clam Tridacna sp.