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