Questions and Answers
What is the visceral mass?
What is the mantle in molluscs?
The dorsal body wall covering the visceral mass.
What are ctenidia?
Comb-like structures in mollusks that function as gills.
The periostracum is associated with which part of the mollusk?
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The prismatic layer of a mollusk shell consists of organic material.
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Define nacreous layer.
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What is conchiolin?
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What does 'counter current exchange' refer to?
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What is the function of the osphradium?
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What is the role of the radula?
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What is the buccal cavity?
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What are adductor muscles in bivalves?
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What do byssal threads do?
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What is a mantle cavity?
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What is the function of hectocotylus?
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Define chromatophore.
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What is a suspension feeder?
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What is an operculum?
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What does the columellar muscle do?
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What is torsion in gastropods?
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Study Notes
Visceral Mass
- Contains the majority of digestive, reproductive, excretory, and respiratory systems in gastropods.
- Includes the mantle cavity, a significant part of the structure.
Mantle
- Dorsal body wall covering the visceral mass in molluscs.
- Often extends beyond the visceral mass, forming flaps.
Shell
- Also known as lamellibranch, refers to bivalves like oysters, clams, scallops, and mussels.
- Composed of two hinged shells with a soft body inside.
Ctenidia
- Comblike structure functioning as a respiratory organ or gill in mollusks.
- Features an axis with rows of projecting filaments for gas exchange.
Periostracum
- Thin organic layer covering the outer shell of many shelled animals, particularly molluscs.
- Commonly seen in snails, clams, and certain cephalopods.
Prismatic Layer
- The middle shell layer of mollusks, primarily made up of calcite or aragonite.
- Provides structural integrity to the shell.
Nacreous Layer
- Iridescent inner layer of some molluscan shells, known as mother-of-pearl.
- Comprised of thin, lustrous sheets deposited over an organic matrix.
Conchiolin
- Tough, insoluble protein secreted by mollusks.
- Forms the organic matrix of the shell, allowing calcium carbonate deposition.
Counter Current Exchange
- Biological mechanism maximizing fluid exchange via opposing fluid flows.
- Effective when there is a concentration gradient between the two fluids.
Osphradium
- Olfactory organ in certain molluscs linked with the respiratory system.
- Tests incoming water for silt and food particles, present in cone snails.
Radula
- Rasp-like structure with tiny teeth used by mollusks to scrape food particles.
- Plays a crucial role in the feeding process.
Odontophore
- Mouth projection supporting the radula in most mollusks.
- Aids in feeding mechanisms.
Buccal Cavity
- The oral cavity and entry point of the alimentary canal.
- Connects to the pharynx and leading to the esophagus in vertebrates.
Auricle
- Ear-shaped appendage projecting from each atrium of the heart.
- Associated with both hearing and cardiac structure.
Ventricle
- Small cavity within a body, often referring to one of the heart's chambers.
- Involves various physiological processes.
Metanephridia
- Tubular excretory organ found in many invertebrates, including mollusks.
- Functions in waste removal and osmoregulation.
Trochophore Larvae
- Free-swimming, planktonic marine larva with several cilia bands.
- Represents an early developmental stage in some mollusks.
Protoconch
- Embryonic or larval shell forming the initial structure in various mollusks.
- Significant for identification and classification purposes.
Veliger Larvae
- Planktonic larval stage of many sea and freshwater snails, as well as bivalves.
- Critical for dispersal and developmental studies in molluscan biology.
Palps
- Segmented appendages near the mouth in many invertebrates.
- Serve roles in sensation, locomotion, and feeding in mollusks.
Adductor Muscles
- Muscles drawing shell valves toward the median axis.
- Essential for closing the shell in bivalves.
Byssal Threads
- Strong filaments enabling bivalve mollusks, like mussels, to attach to surfaces.
- Provide stability and anchorage in marine environments.
Siphuncle
- Calcareous tube in shelled cephalopods, aiding in buoyancy control.
- Allows for fluid transfer between shell chambers.
Mantle Cavity
- Space between the mantle and mollusc's body containing respiratory organs.
- Critical for gas exchange in aquatic environments.
Pen
- Internal cartilaginous structure in squids that provides support.
- Represents a remnant of the ancestral shell.
Hectocotylus
- Specialized arm in male cephalopods for transferring sperm to females.
- Essential for reproduction in cephalopod species.
Spermatophore
- Capsule holding a mass of sperm, transferred from male to female in reproduction.
- Key element in the breeding process among various species.
Chromatophore
- Pigment-containing cells that change color through contraction and expansion.
- Important for camouflage and signaling in cephalopods.
Suspension Feeder
- Organism feeding on suspended materials in water, such as plankton.
- Adaptations include structural modifications for effective food straining.
Operculum
- Secreted plate closing the shell aperture when the gastropod retracts.
- Provides protection against predators and environmental hazards.
Columellar Muscle
- Muscle in gastropods originating from the columella, helping retract into the shell.
- Integral for the gastropod's mobility and protection strategy.
Umbo
- Lateral prominence on a bivalve shell above the hinge.
- Utilized for identifying age and growth patterns in bivalves.
Torsion
- A developmental synapomorphy in gastropods involving 180-degree rotation.
- Affects the arrangement of visceral mass, mantle, and shell concerning the head and foot.
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Test your knowledge on key terms related to Phylum Mollusca with these flashcards. Each card includes definitions of important anatomical features and functions, such as the visceral mass and mantle. Perfect for biology students and enthusiasts looking to reinforce their understanding of mollusks.
