[MARYLAND SEA GRANT - OYSTERS IN THE CLASSROOM
[Glossary of Terms]
Abiotic

All non-living factors within an environment, including physical, chemical, and temporal (time) components.

Also see biotic.
Adductor Muscle

A prominent organ situated in the posterior region of the oyster body, consisting of an anterior translucent part and a smaller, white crescent-shaped region. It functions to close the oyster shells (relaxation of the adductor muscle allows the shells to gape open).
Anus

The opening of the rectum into the cloacal chamber.
Bacteria

Diverse group of organisms composed of a single prokaryotic cell without a nucleus or membrane bound organelles whose most important biological roles are decomposition, nitrogen fixation, and disease agents.
Biotic

All living factors within an environment.

Also see abiotic.
Bivalve

Marine or freshwater mollusk that has two shells.
Cilia

Hair-like structures used for motility in some protozoans and for the movement of particles or fluids in certain cells of more advanced organisms.
Cloacal Chamber

A chamber which passes excess water and waste from the oyster into the environment. In addition, it houses the adductor muscle and rectum.
Commensal Organisms

Organisms that rely on a host for a benefit but does not harm or benefit the host (i.e., an oyster bar provides protection for crabs and a hard substrate for barnacle settlement).


Diatoms

Major phytoplankton group whose organisms are enclosed within a secreted shell of silicon.
Digestive Gland

The gland responsible for the production of digestive enzymes.
Eggs

Haploid gametes produced by females.

Also see sperm.
Epibranchial Chambers

A chamber that is formed by the fusion of the mantle and visceral mass and the base of the gills and houses the gills, mouth and labial palps.
Esophagus

Tube that connects the mouth with the stomach.
Gills

The gills are the largest organ in the oysters body and consists of four folds of tissue. Along with the mantle it is the chief organ of respiration. They create water currents, collect food particles, and move food particles to the labial palps for further sorting. Also serve to separate masses of eggs released from the ovary during spawning into individual ova for efficient fertilization.
Granulocyte

A type of hemocyte that aides in the defense of an organism from foreign bodies and other materials.
Hemocyte

Blood cell found in the hemolymph. There are different types that perform a wide variety of functions from defense to nutrient transport.
Hemolymph

Circulatory fluid found in all mollusks and many other invertebrates.
Hermaphroditic

Possessing physiologically functioning male and female reproductive organs.
Hinge

The area formed by the joined valves at the anterior of the oyster.
Intestine

Organ used for the transport of undigested material and transport of nutrients.
Labial Palps

Consist of two pairs of large, soft flaps that have a roughly triangular shape and have a smooth surface and a rough surface. These specialized organs are known to control the total amount of food ingested, but may also sort food before ingestion, perhaps on the basis of particle size or chemical composition.
Mantle

Two fleshy folds of tissue that cover the internal organs of the oyster and are always in contact with the shells but not attached to them. Its principal role is the formation of the shells and the secretion of the ligament as well as playing a part in other biological functions (i.e., sensory reception, egg dispersal, respiration, reserve stores, and excretion).
Mollusk

Organisms in the phylum Mollusca - invertebrate animals with soft unsegmented bodies usually enclosed in a calcareous shell.
Mouth

The inverted U-shaped slit located between the inner and outer labial palps.
Omnivorous

Organisms that consume a variety of plant and animal materials.
Parasitic Organisms

Organisms that rely on a host for resources and as a result are harmful.
Pericardial Cavity

Cavity containing the heart.
Phytoplankton

Diverse group of minute plants that drift freely within the water column.
Protandrous Hermaphrodites

The development of maleness before the female phase with the ability to change sex throughout their life cycle.
Protozoans

Single celled eukaryotic organisms belonging to the kingdom Protista.
Psuedofeces

Particles which are not sorted as food and are rejected through the mouth.
Pseudopodia

"False feet" that extend from the hemocyte that enable mobility and capture of foreign bodies and other materials.
Rectum

Organ that is the continuation of the intestine; it runs dorsally over the adductor muscle and ends in the anus, and aborts water while consolidating feces.
Shucking

Opening an oyster.
Sperm

Haploid gametes produced by males.

Also see eggs.
Stomach

A large sac-like organ that is divided into two chambers used in the digestion and sorting of food particles.
Tentacles

Small sensory organs attached to the edge of the mantle used for the detection of environmental stimuli.
Umbo

The anterior end of the oyster. It is pointed and the oldest part of the oyster.
Valves

The two shells of the oyster.
Watermen

Individuals who earns an income from harvesting aquatic resources.
Zooplankton

Diverse group of minute animals that drift freely within the water column.