Abstract
The development of cercariae from Schistosoma mansoni strains BH and SJ in Biomphalaria glabrata and Biomphalaria tenagophila treated with saccharose was studied. The molluscs were maintained in dechlorinated tap water containing 0.01% saccharose. After one week of treatment with saccharose, B. glabrata and B. tenagophila were exposed to ten S. mansoni miracidia, from BH and SJ strains respectively. Control snails of both species were maintained in dechlorinated tap water without saccharose and exposed to the same number of miracidia. There was no significant difference between the infection rates of snails treated or not with saccharose. However, the two groups of B. glabrata had significantly greater infection rates than the corresponding B. tenagophila groups. Molluscs treated with saccharose had a lower survival rate, with the greatest mortality occurring immediately before and at the beginning of cercariae release. Treatment with saccharose did not result in the release of more cercariae, but larvae from molluscs so treated showed a greater capacity to penetrate mouse skin, which was attributed to the greater energy supply during larval development in the mollusc.
Highlights
Adult schistosomes accumulate a considerable amount of glycogen, which is continuously produced by the worms in alternating cycles of synthesis and degradation
Pinheiro & Amato (1994) observed that in Bradybaena similaris infected with Eurytrema coelomaticum, the hemolymph glucose levels were lower and there was a reduction in the glycogen content of the digestive gland and cephalopodal mass
We examined the influence of saccharose exposure on the susceptibility of B. glabrata and B. tenagophila to infection by two strains (BH and SJ) of S. mansoni
Summary
Adult schistosomes accumulate a considerable amount of glycogen, which is continuously produced by the worms in alternating cycles of synthesis and degradation. High glycogen consumption is observed in miracidia and cercariae. Cheng & Snyder (1962) showed that glycogen is important for the development of trematode larvae in the snail host since stored glycogen is the main energy source, especially for motility of the cercariae. Christie et al (1974a, b) reported that S. mansoni larvae caused nutritional drainage, including a decrease in glycogen levels, in the intermediate host Biomphalaria glabrata. Release of cercariae by the snails decreased the host’s glucose requirements by 7.5%, which corresponded to the amount of glucose used by the cercariae for the synthesis of proteins, nucleic acids, and lipids. Pinheiro & Amato (1994) observed that in Bradybaena similaris infected with Eurytrema coelomaticum, the hemolymph glucose levels were lower and there was a reduction in the glycogen content of the digestive gland and cephalopodal mass Release of cercariae by the snails decreased the host’s glucose requirements by 7.5%, which corresponded to the amount of glucose used by the cercariae for the synthesis of proteins, nucleic acids, and lipids. Pinheiro & Amato (1994) observed that in Bradybaena similaris infected with Eurytrema coelomaticum, the hemolymph glucose levels were lower and there was a reduction in the glycogen content of the digestive gland and cephalopodal mass
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