Phylum Mollusca Terms Flashcards

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Questions and Answers

What is the visceral mass?

A kind of larva in molluscs

A structure that holds the bulk of the digestive, reproductive, excretory, and respiratory systems (correct)

A type of muscle found in mollusks

A rough outer layer of molluscs

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?

The outermost layer of the shell Signup and view all the answers

The prismatic layer of a mollusk shell consists of organic material.

False Signup and view all the answers

Define nacreous layer.

The iridescent inner surface of some mollusk shells. Signup and view all the answers

What is conchiolin?

A tough protein that forms the organic matrix of the shell. Signup and view all the answers

What does 'counter current exchange' refer to?

A biological mechanism enabling maximum exchange between two fluids. Signup and view all the answers

What is the function of the osphradium?

It tests incoming water for silt and food particles. Signup and view all the answers

What is the role of the radula?

A rasplike structure used for scraping food. Signup and view all the answers

What is the buccal cavity?

The mouth cavity and beginning of the alimentary canal. Signup and view all the answers

What are adductor muscles in bivalves?

Muscles that close the shell valves. Signup and view all the answers

What do byssal threads do?

Attach bivalve mollusks to fixed surfaces. Signup and view all the answers

What is a mantle cavity?

The space between the mantle and the body of a mollusc. Signup and view all the answers

What is the function of hectocotylus?

To store and transfer spermatophores to the female. Signup and view all the answers

Define chromatophore.

A pigment-containing cell that changes color. Signup and view all the answers

What is a suspension feeder?

An animal that feeds on suspended materials in water. Signup and view all the answers

What is an operculum?

A plate that closes the aperture of a gastropod's shell. Signup and view all the answers

What does the columellar muscle do?

Retracts the animal into the shell. Signup and view all the answers

What is torsion in gastropods?

The 180˚ rotation of the visceral mass, mantle, and shell. Signup and view all the answers

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.