Glossary

Crassostrea gigas. Pacific oyster, originally imported by West Coast oyster growers from Japan; it is now cultured in hatcheries.

Crassostrea virginica. Eastern oyster (also referred to as American oyster); inhabits waters from Maine to the Gulf of Mexico.

Cultch. Oyster shell or other material on which free-swimming larvae set and grow.

Dermo, Perkinsus marinus. Protozoan parasite that thrives in high salinities and causes significant oyster dieoffs. Unlike MSX, Dermo is transmitted from one oyster to another.

Eyed larva. Last stage of a freely-swimming oyster that is ready to set, or attach to cultch and undergo metamorphosis to juvenile oyster, or spat.

Growout. The period between setting of oysters and maturity to market size, generally one to three years.

Hemocytes. Disease-fighting cells in the hemolymph of marine invertebrates; analogous to white blood cells in vertebrates.

Hemolymph. Circulatory fluid in invertebrates, comparable to the blood system in mammals.

Immunity. An organism's resistance, natural or acquired, to onset of disease resulting from infection.

Invertebrate. Animals lacking an internal skeleton or spinal column, such as the oyster and crab.

JOD (Juvenile Oyster Disease). An unidentified disease that has primarily affected young oysters cultivated in hatcheries in the northeast.Larva, larvae. Free-living, pre-adult stage of an organism; when first spawned, an oyster larva will swim and feed before it is developmentally ready to seek a permanent home.

MSX, Haplosporidium nelsoni. Parasite that flourishes in high salinity waters and is responsible for heavy oyster kills in mid-Atlantic waters.

Oyster seed. Young oysters that have successfully survived the larval stage and are planted by growers either on private or public grounds.

Parasite. An organism such as MSX or Dermo living on or in another host organism to its advantage and the disadvantage of the host.

Pathogen. Any disease-causing organism.

Protozoan. A single-cell organism, usually free living but sometimes parasitic like MSX.

Selective breeding. Process by which human beings rear animals and plants with particular traits that an organism will pass on to offspring. For example, in oysters, breeding for resistance to disease or for faster growth.

Spat. Young oyster larva that has metamorphosed to become a juvenile oyster.

Spat set. The attachment of oyster larvae to cultch and the successful completion of metamorphosis.

Summer mortality. Mass mortality of Pacific oysters occurring sporadically and inexplicably on west coast oyster grounds -- especially when water temperature rises; thought to be caused by bacteria populations such as Nocardia.