Hagfish Blood Cells and their Formation

Abstract

Hagfishes have a large volume of extracellular fluid. The plasma is iso-osmotic to sea-water and contains organic components in similar concentrations as in other vertebrates. However, the composition of the plasma proteins is poorly known. Suspended free cells in the blood are erythrocytes and leukocytes. Prominent among the latter are granu-locytes, spindle cells, lymphocyte-like cells and immature blood cells (blast cells). Spindle cells and lymphocyte-like cells may to a limited extent resemble lymphocytes but also seem to be progenitors of other blood cells. Erythropoiesis goes on mainly in the circulating blood while granulopoiesis occurs extravascularly around portal vein branches in the intestinal submucosa. The blood coagulates by similar mechanisms as in other vertebrates, but the coagulation factors are insufficiently known. Some kind of thrombocytes are involved.