Carbohydrate metabolism alterations in Biomphalaria glabrata infected with Schistosoma mansoni and exposed to Euphorbia splendens var. hislopii latex

Abstract

Biomphalaria glabrata is the main intermediate host involved in schistosomiasis in Brazil. Studies have shown that physiological stress conditions, such as infection with Schistosoma mansoni, starvation, aestivation and exposure to molluscicides, can alter its carbohydrate metabolism (Schwartz & Carter 1982, Becker 1983, Bezerra et al. 1999, Alcanfor 2001, Mello-Silva et al. 2006a). These changes can alter the glycogenesis, gluconeogenesis and glycolysis in the snail.One of most promising Brazilian molluscicides is the crude extract of Euphorbia splendens (Sin. Euphorbia milii), which under laboratory and field conditions meets the recommendations of the WHO for use as a natural molluscicide (Vasconcellos & Amorim 2003). Mello-Silva et al. (2006a, 2007 studied the influence of sublethal doses of the latex of this plant on the carbohydrate and protein metabolism and reproductive biology of B. glabrata and found strong metabolic changes leading to a reduction in its population and consequently in the transmission of the parasite. In spite of this potential, there are no studies of the influence of this product on the physiology of Biomphalaria infected with S. mansoni.The present paper examines the action of the latex of E. splendens var. hislopii on the glucose content of the haemolymph and on the carbohydrate (glycogen) deposits of B. glabrata (BH strain) infected with S. mansoni (BH strain). MATERIALS AND METHODSObtaining the latex of E. splendens var. hislopiiSamples of E. splendens var. hislopii latex were collected in the autumn from plants cultivated in plots near the Biology Department, Fiocruz, in Rio de Janeiro, Brazil. The latex was collected as described by Vasconcellos and Amorim (2003) on the same day the tests were conducted.Lethal dose experiment -Using the recently collected latex, an aqueous stock solution at a concentration of 100 mg/L was prepared and, from this, solutions of different concentrations were prepared for use in the bioassays. The lethal (LC 90 ) and sublethal (LC 50 ) concentrations were determined according to Vasconcellos and Amorim (2003), as recommended by the World Health Organization (1983) and Mott (1987). The LC 50 and LC 90 values were, respectively, 1.0 mg/L and 2.3 mg/L (Mello-Silva et al. 2006a).Balloon flasks (1000 mL) were used and the latex solution was divided into two 500 mL glass beakers. The groups of B. glabrata (BH lineage), infected and uninfected, respectively, were placed in LC 50 solutions and exposed for 24 h (Vasconcellos & Amorim 2003) at 21ºC. Two glass beakers received 500 mL of distilled water without latex as a control group. None of the snails was fed during this period.After the latex exposure period, the snails were removed from the flasks and rinsed in distilled water to remove the residues. The number of dead specimens was noted. (1990). The snails were grouped according to their infection stage (1 day and 1, 2, 3 and 4 weeks post exposure). In each period analysed, 100 infected and 20 uninfected snails (control) were used. Sixty infected sn...

Total protein and carbohydrate content and protease and disaccharidase activities in the hemolymph of Lymnaea stagnalis naturally infected with digenean larvae

“…According to the reports by other researchers we expected a decreased level of carbohydrates in the hemolymph of infected snails as compared to uninfected ones (after El-Ansary 2003; Jarusiewicz et al 2006;Mello-Silva et al 2010). We obtained such a result but only during week 4 for the snails infected with O. ranae or P. elegans.…”

New scope on the relationship between rotifers and Biomphalaria alexandrina snails

“…Nevertheless, this didn't cause any lethal effect on the snail. This is most probably because glycogen is used to a much lesser extent than lipids to maintain the metabolism of gastropods, thus is not of such significant importance as a reserve [35] . The pathological impact of rotifers isolated from snails has been reported to affect egg masses and newly hatched snails, rather than mature snails [22] .…”

“…Four weeks post infection, histological examination of snails belonging to the SG II-B subgroup revealed several profound changes; the first was the presence of a host tissue reaction of hemocytes enclosing degenerated rotifers, associated with diminution of snail's glycogen. It is well known that rapidly developing cercariae depends on the snail's glycogen stores [35] . Hence, it seems that rotifers entered the snail tissues and consumed the host's glycogen and this is assumed to have hindered the proper establishment of S. mansoni parasites within the snail tissue, as proved by the presence of few developed cercariae together with some malnourished degenerated ones.…”

“…This coincided with the presence of many well developed cercariae together with some degenerated ones. Apparently, the two weeks interval-lapsed before rotifers contamination-allowed the establishment of infection within the snails as nothing competed with the rapidly developing S. mansoni parasites on the snail host's glycogen stores [35] . We assume that upon invasion of the snail tissues with rotifers, the latter started to consume a portion of the snail's glycogen at the expense of the growing parasites.…”

Changes in energetic metabolism of Biomphalaria glabrata (Mollusca, Planorbidae) in response to exogenous calcium

“…Under physiological stress, such as estivation, parasitic infections or exposure to molluscicides, the snails use sources alternative to glucose, like lipids and proteins (Mello-Silva et al, 2010;Tunholi et al, 2013).…”