Phylum Mollusca

Torsion

180 counterclockwise twisting of head and foot in relation to shell and visceral mass. Advantage is unclear: osphradium forward, better gill circulation, creates sweage problem for gills and head

Commercial importance (Class Bivalvia - Phylum Mollusca)

20% of global SW animal harvest groups, clams; oysters; mussels; scallops. Bivalve poisoning (natural problems, red tide and Vibrio vulnificus. pollutants, bacteria, viruses, chemicals)

Chambered Nautiluses-Class Cephalopoda - Phylum Mollusca

80-90 suckerless tentacles, only extant cephalopod with external shell, shallower water at night, deeper by day

operculum

A protective flap that covers the gills of gastropoda

Phylum Mollusca

Bivalves, Chitons, Gastropods, Cephalopods

Ecology and lifestyle (Class Bivalvia - Phylum Mollusca)

Burrowers-clams, boring- use shell and sometimes acid for CaCO3, attachment to substrate, one valve cemented to bottom, byssus, unusual lifestyles (scallops and giant clams)

Statocysts

Cells that control equilibrium and balance

Class Polyplacophore - Phylum Mollusca

Chitons

Class Bivalvia - Phylum Mollusca

Clams and relatives. Bivalve Shell (body laterally compressed) Adductor muscles close valves, hinge ligament opens valves. Sedentary Filter feeders (large gills and mantle cavity, spihons, reduced head and sense organs, radula absent) Reproduction (dioecious, free-swimming trochophore and veliger larvae)

Rams Horn Shell (spirula spirula) -Class Cephalopoda - Phylum Mollusca

Cuttlefish relative, shell is spiral and nautilus-like, common in deep water offshore

dioecious

Having male and female reproductive organs in separate plants or animals

osphradium

Molluscan chemo/touch reception

Phylum Mollusca- Organ Systems

Open circulatory system (hemocoel, no blood pigments) Excretion (Nephridia, kidneys in most) Respiration ( ctenidia, gills, in mantle cavity between mantle and body) Sense Organs (eyes, tentacles and palps, statocysts, osphradia)

Phylum Mollusca- Characteristics

Second in number of species, first in marine habitat. Schizocoelous coelomates. Protostomes. Distictive: soft-bodied, shell of CaCO3 and protein, Mantile secretes the shell, Foot, Radula for feeding

Characteristic-Class Scaphopoda- Phylum Mollusca

Shell shape, adhesive feeding tentacles, burrow in sand/mud often in deep water, share common ancestor with bivalves, shell bivalves initially

Group Prosobranchs- Class Gastropoda- phylum mollusca

Shell with operculum, marine habitat, normal torsion, dioecious reproduction. Examples, lifestyles and feeding

Class Gastropoda- Phylum Mollusca

Snails and relatives, Single coiled shell, Torsion, Reproduction (egg cases or masses. Trochopore passes in egg, veliger or small snail hatches) Commercial importance (queen conch, abalones, escargots)

Phylum Mollusca- Shell production

Structure (Periostracum, Prismatic, Nacreous) Mantle (Lays down protein matrix to 1/3 dry weight, concentrates CaCO3 from blood, shapes and pigments shell) Pearls (lumps of CaCO3)

Phylum Mollusca- Development

Trochophore larva (similar to annelids, often passed in egg) Veliger Larva (velum- ciliated for feeding and locomotion, adult structures appear, shed during settling, glochidia- in FW bivalves are parasitic on fish)

Calcite

White

Class Aplacophora - Phylum Mollusca

Worm-like due to rolled-up mantle, no true shell-spines, scales, spicules, live in/on mud or on cnidarians which they eat, probably primitive, divering before evolution of shell.

Class Cephalopoda - Phylum Mollusca- Motility and Carnivory

cephalopds are motile carnivores. Motility: shell reduced or absent, if present, for suppor or buoyancy funnel for jet propulsion. Carnivory: nervous system largest for any invertebrate, well developed eyes, tentacles/arms, suckers, beak-like jaw, octopuses venomous, blue-ring lethal

Osphradia

chemoreceptors next to ctenidia

Class Polyplacophore- Phylum Mollusca

chitons. Characteristics (shell with 8 valves, conformation to hard substrate. gir

Special Features-Class Cephalopoda - Phylum Mollusca

chromatophores (under nervous control), ink sac, bioluminescence with photophores,

Reproduction- Class Cephalopoda - Phylum Mollusca

dioecious, spermatophore transfer with hectocotylus, gelatinous egg masses, some species die after mating, direct developement

Octopods- intelligence

easy to anthropomorphize, brain/neuron number partially explained by (8 independent arms, chemosensitive suckers, ability to change skin color and texture), difficult to work with, teaching/learning solitary

Squids-Class Cephalopoda - Phylum Mollusca

eight arms and two tentacles, shell is a pen (protein) for support only, fast, agile with fins, predators for fish, giant and colossal squids reach 45-60 ft 1 ton

Octopods - Class Cephalopoda - Phylum Mollusca

eight arms, no tentacles, shell absent, benthic in protective shelter, hunt at night for crabs, intelligent can learn and remember, paper nautilus (a pelagic octopus)

tentacles/arm

extensible for prey capture

Commercial important-Class Cephalopoda - Phylum Mollusca

food, bait

Class Polyplacophore - Phylum Mollusca- Ecology and feeding

herbivores often nocturnal from a home base. Common in high energy rocky habitats

Group Pulmonates- Class Gastropoda- phylum mollusca

land and FW snails, land slugs, FW limpets. Shell lacks operculum, land and FW habitat. Torsion, torted, detorted or untorted. Sexual reproduction, hermaphrodites with ovotestes mantle cavity functions as lungs

Girdle

mantle extension bounden shell

Hectocotylus

modified reproductive arm. specialized structure on the arm of the male octopus; it is responsible for transferring sperm to female

Aragonite

mother-of-pearl

Types of Pearls

natural, cultured, bead

Octopods- Genome Analysis

overall genome same as lower molluscs, massive expansion of two gene families (neuronal development, TF for general elevated gene expression), genomic rearrangements.

Group Opisthobranchs- Class Gastropoda- phylum mollusca

sea hares, sea slugs (nudibranchs), bubble shells, sea butterflies (pteropods). Shell is reduced, internal or absent. Marine habitat. Torsion is torted, detorted, or untorted. Sexual reproduction are hermaphrodites with ovotestes

Class Polyplacophore - Phylum Mollusca- Characteristics

shell with 8 valves, conformation to hard substrate. girdle, broad muscular foot, small head, numerous eyes/sensory tissue in pits in the shell

Class Monoplacophora- Phylum Mollusca

small, limplet-like in deep water, known only as paleozoic fossils until 1952, serial repetition in parts like gills, but secondary derivation, great interest, similar to the ancestral mollusc, polyphyletic

Cuttlefish- Class Cephalopoda - Phylum Mollusca

squid-like, shell is a calcareous cuttlebone, cuttlebone is sold in pet stores, feed on benthic animals

Prismatic

thick, calcareous middle layer

Periostracum

thin proteinaceous layer

Nacreous

thin, smooth calcareous inner layer

byssus

thread-like appendage that attach

Class Scaphopoda- Phylum Mollusca

tooth or tusk shells

Octopods- Research

trained with mild shock or reward to select red or white ball after a five day period of learning

Siphons

used for pumping water, incurrent and excurrent