Oysters . . .
	In the Environment

Oyster Hemocytes
forms, function, and microscope techniques

Mollusks, like many other invertebrates, have an open circulatory system that does not confine blood to traditional vessels like veins, arteries, and capillaries. Instead, an open circulatory system will circulatory blood through a number of cavities and sinuses in various parts of the organism. In an oyster, the hemolymph (blood) is circulated in this way and can be readily found in the pericardial cavity that contains the heart. Within the hemolymph of the oyster there are three basic types of hemocytes that perform a wide variety of functions from defense to nutrient transport.

Oyster hemocyte (100x, oil immersion) with psudopodia extended.   A cell (upper right) is being engulfed.

A readily found hemocyte known as a granulocyte can make a very impressive showing under oil immersion light microscopy. These hemocytes appear to be filled with small "grains" and have long pseudopodia that extend from the outer surface of the cell. The pseudopodia are used for mobility and the capture of foreign bodies and disease causing organisms like dermo, Perkinsus marinus.

The procedure for harvesting hemocytes is simple and requires only a few pieces of equipment. Viewing hemocytes is best accomplished via oil immersion with a 100x objective lens. Lower magnification will allow you to see them but not in great detail. Follow the steps below and you will be able to see these cells live on a glass slide.

http://www.mdsg.umd.edu/Extension/msgsnn/msgsnn02_3/oysters_envi.html