Comparative Studies on the Internal Defense System of Schistosome-Resistant and -Susceptible Amphibious Snail Oncomelania nosophora: 1. Comparative Morphological and Functional Studies on Hemocytes from Both Snails

Abstract

Two morphologically distinct blood cell types (hemocytes), Type I and Type II were found coexisting in hemolymph from two kinds of snails, Oncomelania nosophora strain, viz. from the Nirasaki strain (schistosome-resistant snail) and the Kisarazu strain (schistosome-susceptible snail). Ten min after inoculation of SRBC, the majority of Type I cells from Nirasaki strain flattened and spread over the surface of the glass plate by extending pseudopodia. In the Kisarazu strain, Type I cells adhered to the surface of substrate with spike-like filopodia, but did not form spreading lamellipodia. Type I cell from the Nirasaki strain phagocytosed SRBC but that from the Kisarazu strain did not. The starting time of recognition of foreign materials was slightly different in the Type I hemocytes from the two strains. Type II cells from both strains were round and lymphocyte-like. Ten or sixty min after incubation, Type II cells from neither strain adhered to the surface of substrate or SRBC, and did not phagocytose SRBC. Type II cells from the Nirasaki strain were quite similar to those from the Kisarazu strain. We concluded that Type I cells from the schistosome-resistant snail, Nirasaki strain, possessed higher phagocytic activity than those from the susceptible snail, Kisarazu strain, despite the morphological similarities of the hemocytes from both strains.

Identification of differentially expressed genes in Oncomelania hupensis chronically infected with Schistosoma japonicum

“…The lack of an appropriate schistosome-resistant O. hupensis strain is another reason for the lack of efficient comparative studies. Although O. nosophora from Japan, showed schistosome-resistant (Nirasaki isolate) and schistosome-susceptible (Kisarazu isolate) responses to the S. japonicum Philippines strain (Sasaki et al, 2003, both isolates of O. nosophora showed high susceptibility to Japanese strain of S. japonicum . Considering local adaptation in host-parasite systems (Kaltz and Shykoff, 1998;Lively et al, 2004;Brandt et al, 2007), O. nosophora may not be representative of other natural Oncomelania populations including that from China, which is used as a schistosome-resistant and schistosome-susceptible strain in studies of the O. hupensis-S. japonicum interaction.…”

Histopathological study on susceptible and resistant Bulinus truncatus snails to infection with Schistosoma haematobium

“…Electron microscope studies of the relation between sporocysts and snail cells are limited and possibly rare. The general morphology of the body wall of the sporocysts of S. haematobium does not differ essentially from that of most sporocysts or radiae described in the ultrastructural level (Kirinoki et al, 2000;Sasaki et al, 2003;Remy and Arouna, 2005). However, some sporocysts have been described as possessing an external nucleated layer outside the tegument.…”

“…The speed and severity of encapsulation responses against trematode larvae have been hypothesized to reflect the degree of host resistance, with rapid encapsulation and destruction being interpreted as evidence of strong resistance (Kirinoki et al, 2000;Sasaki et al, 2003;Azevedo et al, 2006). Accordingly, resistance in B. truncatus has not been deemed strong because the hemocytic reaction is unimpressive and dead parasites persist for some time.…”

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

“…Haemolymph was collected by removing the tail portion of the snail at first, and then a pair of pliers was used to gently crush the snail shell. The total dregs were placed into a small beaker (5 mL) to which an equal volume of saline-antibiotic (SA) solution pH 7.2 (1.16M NaCl, 0.15M Na 2 HPO 4 , 0.15M KH 2 PO 4 , 100U/mL penicillin and 100 µg/mL streptomycin) was added (Sasaki et al 2003) and stirred to suspend haemolymph. The haemolymph suspension was transferred into a 1.5-mL filter micro-tube (sieve diameter: 30 µm) and centrifuged at 2000 rpm for 10 minutes.…”

“…(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. Morphological classification of gastropod haemocytes has been based on optical and electron microscopy studies (Sasaki et al 2003;Walker et al 2010;Cavalcanti et al 2012), flow cytometry (Travers et al 2008;Donaghy et al 2010;Barçante et al 2012), functional studies (Cheng 1984), density gradient centrifugation (Adema et al 1994), antibody binding (Yoshino & Granath 1985) and enzyme markers (Granath & Yoshino 1983).…”