All molluscs are characterized by having three main body regions?
Head-foot, which is the sensory and locomotor part of the body; a visceral mass, containing most of the organ systems; and a mantle, which covers the visceral mass and secretes the shell.
Largest classes of molluscs are?
Gastropoda (snails and their relatives), Bivalvia (clams, oysters, and others), Polyplacophora (chitons), and Cephalopoda (squids, octopuses, nautiluses).
Smaller classes molluscs are?
Monoplacophora, Scaphopoda (tusk shells), Caudo- foveata, and Solenogastres.
Most molluscs also have?
Radula, a rasping structure covered with chitinous teeth, which is used in feeding.
Molluscs are probably closest phylogenetically to?
Annelids (earthworms or leech).
Annelids and molluscs have very similar developmental patterns and a similar type of ciliated larva, called a?
Trochophore larva. But not segmented like annelids.
Symmetry?
Bilateral
Coelom and Body Organization?
Well-developed coelom
Germ Layers and Development?
- Three germ layers: ecto-, meso-, endoderm
- Protostome
Respiratory system?
Sinuses collect hemolymph and transport to ctenidia for gas exchange..
Circulatory system?
Open circulatory system; hemocyanin dissolved in plasma; lymphocytes present; a few bivalves and gastropods use hemoglobin and have erythrocytes; dorsal heart beats rhythmically to create pressure; hemolymph forced into aorta and carried into tissues by o
Skeletal system?
Hard exoskeleton; outer organic layer rests on layers of calcium carbonate; exoskeleton reduced or absent in most cephalopods.
Nervous system?
Limited cephalization, except cephalopods, which have giant nerve cells, complex sensory system with image forming eyes and complex behavior.
Digestive system?
- Complete; specialized for filtering small food particles from water.
- Cilia lining ctenidia draw water into mantle cavity through incurrent siphon; from mantle, labial palps direct food to mouth; esophagus, stomach, digestive glands; waste exits anus i
Excretory system? How does it poop?
Nitrogenous wastes excreted into excurrent siphon by pair of kidneys; some ammonia eliminated by ctenidia.
Reproduction?
- Sexual; dioecious
- Pair of gonads empties gametes into excurrent siphon. - Some are Monecious, both sexes. Like in snails.
Defense?
- Burrowing with muscular foot; hard exoskeleton (shell-reduced in cephalopods).
- Ink used by some cephalopods.
Locomotion?
Muscular foot
Soft Bodied; Many With Protective Shell
Synapomorphies
More Species Of Molluscs In Ocean Than Any Other Phylum, Over 200,000 Sp.
Synapomorphies
The Mantle Is A Thin Tissue Layer Covering Body That Secretes Shell
Synapomorphies
The Foot Allows Locomotion Or Attachment
Synapomorphies
Most Have A Head With Eyes
Synapomorphies
The Radula Is A Tooth Like Structure Used For Feeding
Synapomorphies
Ancestral Larvae Is a Trocophore; Some Produce a Veliger
Synapomorphies
Open Circulatory System
Synapomorphies
Gastropods, Bivalves, Cephalopods, And Chitons
Synapomorphies
The molluscs include a number of familiar animals, including?
Snails, oysters, clams, octopuses and squids.
Larval Forms?
Trocophore and Veliger
Trocophore?
The planktonic larva .
Veliger?
Final larval stage.
Phylum Mollusca Classes (from lecture)
Class Caudofoveata
Class Solenogaster
Class Monoplacophora
Class Polyplacophora
Class Scaphopoda
Class Gastropoda
Class Bivalvia
Class Cephalopoda
Class Polyplacophora means?
Many plates on a foot.
Class Cephalopoda means?
Head foot.
Cephalopoda is characterized by?
Its bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot.
Class Gastropoda means?
Stomach
Class Scaphopoda means?
Tusk shell
Class Bivalvia means?
Hatchet foot
Which evolved from sea and moved on to brackish and freshwater habitats?
Bivalves and gastropods.
How many of these specimens posses a radula (horny tooth-bearing strip on the tongue of molluscs that is used for rasping food)?
Gastropods, Cephalopoda, Mono-, A- & Polyplacophora
Which ones are filter feeders?
Bivalvia (Scaphopoda....have a captacula)
Which have undergone torsion? Detorsion?
Gastropods Opisthobranchia (sea hares & sea
slugs) and the land slugs of the Pulmonata
Name the main function of the mantle?
Mantle secretes the shell.
Name a class used for currency?
Scaphopoda.
Which specimens have lungs? (Just have think of which live on land vs. in water......)
Pulmonata - their name gives this away.
Name the oldest part of a univalve shell? Bivalve?
Apex for Univalve, Umbo for bivalve but often the terms are used interchangeably.
Class Monoplacophora
Kingdom: Animalia
Phylum: Mollusca
(unranked): Monoplacophora
Odhner, 1940
Big Characteristics: Serially repetition
What does sapient mean?
Wise, capable of emotional knowledge.