Differences in the number of hemocytes in the snail host Biomphalaria tenagophila, resistant and susceptible to Schistosoma mansoni infection

Abstract

ABSTRACT. The relationships between schistosomiasis and its intermediate host, mollusks of the genus Biomphalaria, have been a concern for decades. It is known that the vector mollusk shows different susceptibility against parasite infection, whose occurrence depends on the interaction between the forms of trematode larvae and the host defense cells. These cells are called amebocytes or hemocytes and are responsible for the recognition of foreign bodies and for phagocytosis and cytotoxic reactions. The defense cells mediate the modulation of the resistant and susceptible phenotypes of the mollusk. Two main types of hemocytes are found in the Biomphalaria hemolymph: the granulocytes and the hyalinocytes. We studied the variation in the number (kinetics) of hemocytes for 24 h after exposing the parasite to genetically selected and non-selected strains of 2437 ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 9 (4): 2436-2445 (2010) Differences in the number of hemocytes in B. tenagophila Biomphalaria tenagophila, susceptible or not to infection by Schistosoma mansoni. The differences were analyzed referred to the variations in the number of hemocytes in mollusks susceptible or not to infection by S. mansoni. The hemolymph of the selected and non-selected snails was collected, and hemocytes were counted using a Neubauer chamber at six designated periods: 0 h (control, non-exposed individuals), 2 h, 6 h, 12 h, 18 h and, 24 h after parasite exposure. Samples of hemolymph of five selected mollusks and five non-selected mollusks were separately used at each counting time. There was a significant variation in the number of hemocytes between the strains, which indicates that defense cells have different behaviors in resistant and susceptible mollusks.

Resistance of Biomphalaria glabrata 13-16-R1 snails to Schistosoma mansoni PR1 is a function of haemocyte abundance and constitutive levels of specific transcripts in haemocytes

“…Among known facts are that snail size can influence infectivity rates: some strains of B. glabrata are susceptible as juveniles but resistant as adults (Richards et al, 1992), and larger snails exposed to S. mansoni have lower infection levels than smaller snails of the same age (Niemann and Lewis, 1990). Circulating snail haemocytes play a key role in immune surveillance (Oliveira et al, 2010) and will migrate from the haemolymph into the tissues after parasitic infection (Noda and Loker, 1989; Martins-Souza et al, 2009; Barçante et al, 2012). This change is most intense in resistant snails in which larger haemocytes nearly disappear from the haemolymph, while small cells gradually increase (Martins-Souza et al, 2009).…”

Hemocyte subpopulation changes in Bithynia snails infected with Opisthorchis viverrini in Thailand.

“…vasorum (Barcante et al, 2012). After that, the number of hemocytes was reestablished at 10-15 days after infection (Seta et al, 1996;Bezerra et al, 1997;Oliveira et al, 2010). This trend is possibly a result of the snail´s immune response, which is initiated with the first parasite infection and continued until parasites were eliminated, hence showing variation in the number of hemocytes in the hemolymph of infected snails.…”

“…Experimental studies have emphasized the positive effect of parasitic infections on the number of hemocytes in the hemolymph of various species (McReath et al, 1982;Bezerra et al, 1997;Ordas et al, 2000;Oliveira et al, 2010;Santos et al, 2011;Barcante et al, 2012). Furthermore, differences in the cell proportion occur often.…”

Morphological and structural characterization of haemocytes ofOncomelania hupensis(Gastropoda: Pomatiopsidae)

“…(S.M. Soomro et al 2005;Oliveira et al 2010), as well as in Lymnaea spp. (Monteil & Matricon-Gondran 1993; Van der Knaap et al 1993;Russo et al 2008), but very few reports regarding O. hupensis (H.M. Zhang et al 2007), calling for more research.…”