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Muscle(s) in bivalves attached to both shells (valves); adductor muscles pull the two shells together (closes the shells). An elastic hinge pushes the shells apart (opens the shells).

A mollusc with two valves, or shells, joined together by a hinge. Members of Class Bivalvia ("two valves") can be found in freshwater and saltwater. Examples include clams, scallops, oysters and mussels.

An animal that reproduces by expelling (releasing) eggs or sperm (or eggs and sperm) into the surrounding water resulting in external fertilization.

A mass of strong, silky filaments by which certain bivalve molluscs, such as mussels, attach themselves to rocks and other fixed surfaces.

A marine mollusc with a well-developed head surrounded by a ring of eight or more arms. Members of Class Cephalopoda ("head-footed") have a well-developed nervous system and propel themselves by jetting water through a siphon. They include pelagic (open water) and bottom dwellers. These animals maybe shell-less such as the octopus, possess an internal shell (squid and cuttlefish), or they may have an external shell (chambered nautilus).

Structures found along the upper body on several nudibranchs that are used for respiration or defense.

An animal that filters phytoplankton from the water for food. Most filter-feeding molluscs pump water across their gills, which act like fine-screen filters. A pair of tube-like structures called siphons (inhalant and exhalent) allows burrowing bivalves to reach the water column without leaving the safety of their burrow.

A mollusc with well-developed foot, head and body. Class Gastropoda ("stomach-footed") is the largest group of molluscs and can be found in terrestrial, freshwater and saltwater habitats. Members of this group may be shell-less (slugs and sea hares) but typically possess a spiral-shaped shell (snails or conch).

Regions where recreational fishing is allowed (open) or prohibited (closed) during certain times of the year.

Having both female and male reproductive organs.

A nonnative species that is deliberately introduced into an area or inadvertently brought into a region as a result of human activities.

An introduced species that threatens economic or environmental harm to ecosystems, habitats or species. Only some introduced species become harmful.

An animal that developed without a vertebral column (backbone).

The act of bringing an animal (fish, scallop, lobster, etc.) ashore.

A population composed of smaller, isolated populations.

Any number of a large group of saltwater, freshwater and terrestrial invertebrate animals that includes snails, slugs, clams, scallops, oysters, octopuses and squids.

A species that is not indigenous, or naturally occurring, in a region.

A shell-less gastropod commonly called a sea slug.

A specialized term for molluscan planktonic (drifting) larvae. This stage follows the veliger stage and is when the foot becomes well developed.

An organism that lives in open water rather than on the bottom.

Develops male reproductive organs initially and female reproductive organs at a later time.

Tongue-like structure found in many gastropods used to scrape or cut food before eating.

Long, stalk-like structures found on the head of several sea slugs, including sea hares and nudibranchs, that are extremely sensitive organs used as scent or taste receptors.

Juvenile bivalve. Bivalves at this stage are often attached to other structures.

A very early larval stage of molluscs in which the body is ringed by a band of cilia (tiny hairs).

A specialized term for molluscan planktonic (drifting) larvae. Although they do not always have the same appearance as in adults, the shell and most organs can be seen.