Ultrastructurally different hemocytes in a spider

Hemocytes found, in association with the heart of the tarantula spider, Eurypelma marxi Simon, were examined with a transmission electron microscope. Three main ultrastructural types were described. These were designated as granular, oenocytoid, and plasmatocytoid on the basis of similarities to insect hemocytes. In addition, two presumed transitional hemocytes were found. One showed characteristics of both plasmatocytoids and granular hemocytes; the other possessed features common to both plasmato-cytoids and oenocytoids.