Morphological and cytochemical characterization of female Anopheles albimanus (Diptera : Culicidae) hemocytes

Hemocytes of 2- to 3-d-old female Anopheles albimanus Wiedemann are describ ed by morphology, cytochemistry, and functional criteria. Supplemented Grac e's insect medium in a modified Foley's perfusion method was used to obtain hemolymph from An. albimanus. Morphological analysis indicated 3 types of hemocytes were present, prohemocytes, plasmatocytes, and granular cells. Pr ohemocytes were small round cells with a high nuclear/cytoplasmic ratio. Pl asmatocytes were the most abundant cell type in the hemolymph, and appeared as small to large and spindle-shaped cells with round or elongate nucleus, variable number of vacuoles, small granules, and pseudopodia. Granular cel ls were small to large and round with a large number of cytoplasmic granule s, vacuoles, and numerous filopodia. Ultrastructurally, prohemocytes were u ndifferentiated with abundant free ribosomes and a with few small electron- dense granules. Plasmatocytes were rich in mitochondria, rough endoplasmic reticulum, free ribosomes, small electron-dense granules, numerous peripher al vacuoles and with an important organelle polarization. Granular cells co ntained numerous large electron-dense granular inclusions and vacuoles. Cyt ochemical studies showed that plasmatocytes and granular cells have cationi c bactericidal proteins. Only granular cells showed phenoloxidase and proba bly lysosomal activities. In vitro functional studies demonstrated that bot h plasmatocytes and granular cells were able to attach to glass slides, and only plasmatocyte had phagocytic activity and motility. These results char acterize the hemocytes of An. albimanus and suggest that plasmatocytes and granular cells may have a role in defense responses to foreign organisms.