Mollusk Biology and Classification

This set of vocabulary flashcards covers the evolutionary history, anatomical structures, physiological processes, and major classes of the phylum Mollusca.

Mollusca

The phylum of soft-bodied animals that typically have an internal or external shell, originating more than $600$ million years ago.

Trochophore

A free-swimming larva characterized by a ring of cilia and a top-shaped body, found in both mollusks and segmented worms (Annelida).

Molluscus

The Latin word meaning "soft," from which the name of the phylum Mollusca is derived.

Foot

A soft muscular part of the mollusk body plan used for crawling, burrowing, or capturing prey; it often contains the mouth.

Mantle

A thin, delicate tissue layer that covers most of a mollusk's body like a cloak.

Shell

A structure produced by glands in the mantle that secrete calcium carbonate ($CaCO_3$).

Visceral Mass

The section of a mollusk's anatomy located just beneath the mantle that contains the internal organs.

Radula

A tongue-shaped structure used for feeding that consists of a layer of flexible skin with hundreds of tiny teeth supported by cartilage.

Filter Feeders

Mollusks such as clams, oysters, and scallops that use feathery gills and sticky mucus to sift phytoplankton from water.

Gills

Organs used for respiration in aquatic mollusks and for sifting food in filter-feeding species.

Open Circulatory System

A system where blood is pumped into open spaces called sinuses rather than staying entirely within vessels; typical of slow-moving mollusks like snails.

Closed Circulatory System

An efficient transport system where blood always moves inside vessels, found in fast-moving mollusks like octopi and squids.

Nephridia

Simple tube-shaped excretory organs used to remove nitrogen-containing ammonia from the blood.

Statocysts

Simple sensory organs used by mollusks to maintain balance.

Ocelli

Simple eyespots used by mollusks like clams to sense their environment.

Hermaphrodites

Organisms, such as many snails, that possess both male and female reproductive organs.

Gastropoda

A class of mollusks whose name means "stomach foot," characterized by a broad muscular foot on the ventral side; includes snails and slugs.

Nudibranchs

Sea slugs that lack shells and are often brightly colored as a warning of their poisonous or bad-tasting chemical defenses.

cephalopods

means head foot