On the origin of the Biomphalaria glabrata hemocytes

Abstract

A histologic, morphometric and ultrastructural study performed on Biomphalaria glabrata submitted to infection with Schistosoma mansoni miracidia failed to provide significant evidences that the so-called amebocyte-producing organ (APO) is really the central organ for hemocyte production. In infected snails no general reactive changes appeared in the APO, the mitoses were seen only occasionally, and the possibility of cellular hyperplasia was ruled out by morphometric measurements. Under the electron microscope the APO cells presented an essentially epithelial structure, without features indicative of transition toward hemocytes. On the other hand, the present findings pointed to a multicentric origin for the mollusck hemocytes, as earlier studies had indicated. Dense foci of hemocyte collections appeared sometimes around disintegrating sporocysts and cercariae in several organs and tissues of the infected snails, including a curious accumulation of such cells inside the ventricular cavity of the heart. In the heart and other sites, features suggestive of transformation of vascular space endothelial lining cells into hemocytes were apparent. To some extent, the postulated multicentric origin for B. glabrata hemocytes recapitulates earlier embryologic findings in vertebrates, when mesenchymal vascular spaces generate the circulating and phagocytic blood cells

Ultrastructural characterization of cells in primary cultures from different adult tissues of Biomphalaria tenagophila TAIM, a strain that is absolutely resistant to Schistosoma mansoni infection

“…12) were undistinguishable from those obtained in APO culture [Barbosa et al, 2006b]. Taking into account the close anatomical position of the APO and the SK within the reno-pericardial region, and difficulties inherent to APO dissection [Souza and Andrade, 2006], we cannot discard the possibility of contamination of previous APO cultures with SK tissue.…”

Insights from an Integrated View of the Biology of Apple Snails (Caenogastropoda: Ampullariidae)

“…Many authors have reported that gastropod hemocytes are generated in the circulation (Sminia, 1981;Monteil & Matricon-Gondran, 1991;van der Knaap et al, 1993;Souza & Andrade, 2006). However, "amoebocyteproducing organs" have also been reported in the pericardial wall of some heterobranchs (Lie et al, 1975;Rondelaud & Barthe, 1982;Jeong et al, 1983;Ruellan & Rondelaud, 1992) and in the roof of the lung of M. cornuarietis (see Yousif et al, 1980).…”

Haematopoiesis in molluscs: A review of haemocyte development and function in gastropods, cephalopods and bivalves

“…Souza and Andrade (2006, 2012) [63, 64] have proposed an alternative function for the APO in B. glabrata , i.e., renal absorption and filtration. This hypothesis is based in part on ultrastructural observations that there are no “transitional forms” between mantle epithelial cells and haemocytes [64], and that the APO “vaguely resembled the juxtaglomerular apparatus” of the vertebrate kidney [63].…”