Morphological characterization of the hemocytes of the pulmonate snail Biomphalaria tenagophila

Abstract

The blood cells of the pulmonate snail Biomphalaria tenagophila, an important transmitter of the trematode Schistosoma mansoni in Brazil, were examined by light and transmission electron microscopy (TEM). Two hemocyte types were identified: hyalinocytes and granulocytes. Hyalinocytes are small young (immature), poorly spreading cells, which have a high nucleocytoplasmic ratio and are especially rich in free ribosomes. They do not appear to contain lysosome-like bodies and represent less than 10% of the circulating hemocytes. Granulocytes are larger hemocytes which readily spread on glass surface and which strongly react to the Gomori substrate, indicating the enzyme acid phosphatase usually found in lysosomes. Ultra-structurally, they contain a well-developed rough endoplasmic reticulum, dictyosomes and some lysosome-like dense bodies. Granulocytes do not exhibit a characteristic granular aspect and the few granules observed in the cytoplasm should correspond to a lysosome system. They were named granulocytes instead of amoebocytes to use the same terminology adopted for Biomphalaria glabrata in order to make easier comparative studies. This is a preface study for more specific investigations on the functional activities of the blood cells of B. tenagophila and their interactions with the trematode parasite.

Primary culture of the region of the amebocyte-producing organ of the snail Biomphalaria glabrata, the intermediate host of Schistosoma mansoni

“…The youngest cells are rounded and highly active for mitoses, whereas the mature ones display cytoplasmatic indentations, low mitotic and high phagocytic activities. The presence of two sub-populations of hemocytes mainly differing in size, phagocytic activity and ability to emit pseudopods, was demonstrated by others (Cheng & Auld 1977, Van der Knaap & Loker 1990, Barraco et al 1993, Johnston & Yoshino 2001. On the other hand, three hemocyte cell types were described by Matricon-Gondran and Letocart (1999).…”

“…A significant number of authors have reported the presence of two sub-populations of hemocytes, the so called granulocytes and hyalinocytes (Cheng & Auld 1977, Van der Knaap & Loker 1990, Barraco et al 1993. With 5 to 8 µm in diameter and a large nucleus to cytoplasm ratio, the hyalinocytes have a circular contour when in contact with polished glass surfaces, little tendency to form pseudopods and scarce lysosomal structure.…”

“…On the other hand, the granulocytes have diameters between 7 and 11 µm with more cytoplasm. They emit pseudopods, are active in phagocytosis and represent more than 90% of the circulating cells (Barraco et al 1993). This observation explains why a single cell population, was observed in the hemolymph of B. glabrata, most probably corresponding to this major population (granulocytes).…”

Extra-cellular matrix changes in Schistosoma mansoni-infected Biomphalaria glabrata

“…Probably, the round and spreading cells distinguished in stained preparations are the hyalinocytes and granulocytes described by various authors (Cheng 1975, Yoshino 1976. In peripheral lymph preparations, these cells differ greatly with respect to the development of their organelles (pseudopodia, Golgi bodies, lysosomes) (Barracco et al 1993).…”

Hemocyte production in Biomphalaria glabrata snails after exposure to different Schistosoma mansoni infection protocols

“…bacteria ; their cytoskeletal mobility and the adaptations of their plasma membranes encapsulate foreign 15 organisms , and these cells also cooperate with several humoral defense factors. There have been many studies that have attempted to elucidate the complex parasite/host 16,17,18,19 interaction in this model .…”