Morphological and Cytochemical Studies of the Hemocytes of Squilla Mantis (Stomatopoda)

Abstract

ABSTRACT The blood cells of the stomatopod Squilla mantis were examined by light and transmission electron microscopy (TEM). Three hemocyte types were identified: hyaline cells (HC), small granule hemocytes (SGH), and large granule hemocytes (LGH). HC are the smallest cells and are easily recognized by their high nucleocytoplasmic ratio. TEM analyses show that these cells sometimes have a well-developed rough endoplasmic reticulum and always contain numerous small electron-dense granules. Two classes of small granule hemocytes (SGH-A and SGH-B) are distinguished. SGH-A have a dense cytoplasm which usually contains dictyosomcs and numerous granules with a striated substructure. SGH-B are ultrastructurally very similar to the LGH, but their granules are smaller and less electron-dense. SGH are especially rich in lysosomes. LGH are characterized by a high content of large electron-dense granules and characteristic electron-lucent cytoplasmic masses. These scattered masses are also observed in SGH-B. The granules of SGH and LGH are rich in carbohydrates. HC is the predominant cell type in circulation (approximately 40%) while LGH (approximately 20%) and SGH (SGH-A 12% and SGH-B 28%) are less abundant. The total hemocyte number was estimated in males (23,430 cells/mm') and females (35,760 cells/mm3). Most of the studies on the identification of crustacean hemocytes have been carried out in decapods. Studies on the blood cells of other crustacean orders, such as the stomatopods, are needed for the establishment of a more unified hemocyte classification within crustaceans.