Morphological features of sessile and circulating hemocytes in the cephalon of Gammarus setosus dementieva (Crustacea: Amphipoda) by light and electron microscopy

An aggregation of sessile spherulocytes in the cephalon of female Gammarus setosus surrounds the ramifications of the dorsal aorta and the peripheral ganglion of the frontal organ nerve. It is not a hemopoietic organ. The spherulocytes are of three distinct varieties that may represent phases of a secretory cycle possibly synchronized with molting or reproduction. In addition, four other hemocyte types were identified in the cephalic blood sinuses: prohemocyte, plasmatocyte, granulocyte, and adipohemocyte. The cellular and nuclear dimensions of these hemocytes were analyzed. They were shown to be uniform in cell size with average cell area of 69.27 μm², and average maximum cell diameter of 11.75 μm. The mean nuclear area and mean maximum nuclear diameter of the prohemocyte are significantly larger than those of the other cell types. The structure of the hemocyte types is described and compared to those of other crustaceans and insects.