Phylum Molluscs https://www.youtube.com/watch?v=0a7j5prL8hc

General Name means soft, or soft body this is one of the largest animal phyla, besides Arthropoda There are nearly 75,000 species and some 35,000 fossil species Very diverse group (chitons, snails, clams, octopuses) Range from simple organisms to some of the most complex invertebrates Size from microscopic to huge (18 m giant squid) 80% of molluscs are less than 5 cm

Molluscs Classes Class Polyplacophora: Chitons Class Gastropoda Class Bivalvia (Pelecypoda) Class Cephalopoda

Hawaiian Bobtail Squid

Blue Ringed Octopus

Giant Squid

Ecological Relationship great range of habitats – from tropics to polar, altitudes exceeding 7000 m, ponds, lakes, streams, surf, ocean depths, etc Most live in the sea Include herbivores, carnivores, and ciliary filter feeders Originated in the sea

Economic Importance many are food for humans produce pearls (most from Eastern Asia) Some molluscs are destructive (Great Lakes, Snails and Slugs in gardens)

Form and Function Body Plan – consist of head-foot portion and a visceral mass head-foot portion – contains feeding, cephalic sensory, and locomotor organs visceral mass – contains digestive, circulatory, respiratory, and reproductive organs

Form and Function Body Plan – two folds of skin make up a protective “mantle” they enclose a space between the mantle and body wall called the “mantle cavity” it houses gills or lungs mantle also secretes a shell in many species

Form and Function Head-foot – many have well developed head containing sensory organs range from simple to complex eyes posterior of mouth is usually the foot (chief locomotor organ)

Form and Function Head-foot – Unique structure inside mouth called “radula” It is a rasping, protrusible, tonguelike organ found in all molluscs except bivalves It is a ribbon-like membrane on which are mounted rows of tiny teeth that point backward Complex muscles move the radula and its supporting cartilage (odontophore) in and out while the membrane is rotated It has about 250,000 teeth When protruded, it can scrape, pierce, tear, or cut food material

Radula (Slug Eating)

Form and Function Head-foot – Foot can be adapted for locomotion, attachment, or a combination of functions Usually a ventral, solelike structure in which muscular contractions create a creeping movement Some modifications include – “hatchet foot” of bivalves, funnel for jet propulsion in squids and octopuses

Form and Function Visceral Mass – (mantle and mantle cavity) mantle – a sheath of skin extending from the visceral hump that hands down each side of the body, protecting soft parts and creating a space

Form and Function Visceral Mass – (mantle and mantle cavity) mantle cavity – houses respiratory organs products from digestive, excretory, and reproduction systems empty into the mantle cavity in aquatic species, surface cilia create water currents that continually flush out waste

Form and Function Visceral Mass – Shell (when present) typically has three layers Periostracum – outer organic layer Composed of a protein called “conchiolin” Growth only occurs at the margin of the shell Prismatic layer – middle layer Composed of densely packed prisms of calcium carbonate in a protein matrix Nacreous layer – Composed of calcium carbonate sheets laid down over a thin protein matrix This layer is continuously secreted by mantle surface, so it becomes thicker during the animals life Calcium for the shell comes from environmental water, soil, or food

a. Periostracum, b1. Prismatic layer, b2. Nacreous layer

Form and Function Internal Structure and Function – there is an open circulatory system pumping heart blood vessels blood sinuses most cephalopods have closed circulatory system

Form and Function Internal Structure and Function – Digestive tract is complex and highly specialized according to feeding habits Most have a pair of kidneys (metanephridia) Ducts of kidneys in many forms serve to discharge eggs and sperm

Form and Function Internal Structure and Function – Nervous System consists of several pairs of ganglia with connected nerve cords Most molluscs are dioecious Some gastropods are hermaphroditic Many aquatic species pass through free-swimming “trochophore” and “veliger” larval stages

Trochophore

Veliger

Mating Leopard Slugs https://www.youtube.com/watch?v=FhVi4Z6CjZk

Class Polyplacophora: Chitons are somewhat flattened and have a convex dorsal surface that bears eight plates, or valves name means “bearing many plates” most are between 2 and 5 cm commonly occur on rocky surfaces in intertidal regions if detached, they can roll up like an Armadillo for protection Sexes are separate Eggs are released singly or in strings or masses of jelly

Class Gastropoda (gastro – stomach, podos – foot) By far the largest and most diverse class Contains about 40,000 living species Includes snails, limpets, slugs, whelks, conchs, periwinkles, sea slugs, sea hares, sea butterflies, etc. Often sluggish, sedentary animals Because of heavy shells and slow locomotor organs

Snails

Snails

Limpets (Owl Limpet)

Limpets

Slugs

Whelks

Whelks (Lightening)

Conchs

Conchs

Conchs

Periwinkles

Periwinkles

Sea slugs

Sea slugs

Sea slugs

Frosted Sea Slug

Sea hares

Sea hare

Sea hare

Sea butterflies

Class Gastropoda Basically bilaterally symmetrical, but because of “torsion,” the visceral mass is asymmetrical Torsion – a twisting process that occurs during development

Class Gastropoda Three subclasses – Prosobranchia (largest) Almost all marine Periwinkles, limpets, whelks, conchs, abalones, slipper shells, oyster borers, rock shells, cowries Opisthobranchia Sea slugs, sea hares, nudibranchs, canoe shells Pulmonata Mostly land and freshwater snails and slugs Usually lack gills Mantle cavity becomes a lung Usually have two pairs of tentacles, with the posterior pair bearing eyes

Nudibranchs

Nudibranchs

Class Bivalvia (Pelecypoda) (two-shelled) Includes mussels, clams, scallops, oysters, shipworms Most are sedentary “suspension feeders” Unlike gastropods they have no head, radula, and little cephalization

Class Bivalvia (Pelecypoda) Most are marine, but many live in brackish water and in stream, ponds, and lakes Their two shells (valves) are held together dorsally by a “hinge ligament” “Adductor muscles” work in opposition to the hinge ligament and draw the valves together Zebra mussels (pg 194)

Zebra mussels (Lake Mead)

Preventing Mussels in Idaho https://www.youtube.com/watch?v=J4EVAy8ad Mk

Class Cephalopoda most complex species include squids, octopuses, nautiluses, cuttlefishes All are marine All are active predators Have an odd body plan Develops as the embryonic head and foot become indistinguishable The ring around the mouth bears arms and tentacles

Class Cephalopoda Range from 2 to 3 cm to largest of all invertebrates (giant squid) Giant squid (pg 194)

Giant Squid

Slash marks from Giant Squid

The Search for the Giant Squid https://www.youtube.com/watch?v=EbubjXsA4S4

Class Cephalopoda Most have special pigment cells called “chromatophores” in their skin By expanding and contracting, they produce color change Some color change are for protection to match the background Most change is behavioral, associated with alarm or courtship Many deep-sea squid are bioluminescent When the animal is alarmed, it releases a cloud of ink through the anus to form a “smokescreen” to confuse an enemy

Squid

Mimic Octopus and others https://www.youtube.com/watch?v=t- LTWFnGmeg&feature=related

Octopuses

Octopuses

Octopuses

Blue Ringed Octopus The most venous octopus. This small mollusc lives in warm, shallow reefs off the coast of Australia, new Guinea, Indonesia and the Philippines.  It has a life span of about one and a half years.

Blue Ringed Octopus It is said that the venom of this octopus could kill 26 adults in just a few minutes. There is no antivenin for treatment. Fortunately, these octopuses do not attack humans. Injury typically occurs when a blue-ringed octopus is stepped on or picked up.

Smart Veined Octopus using Tools

Giant Pacific Octopus vs. Spiny Dogfish Shark

Nautiluses

Nautiluses

Nautiluses

Chambered Nautilus

Diving for Nautilus

Cuttlefishes

Cuttlefishes

Cuttlefishes

Cuttlefish Attacks