The behavioral effects of antibiotic treatment on the snail Biomphalaria glabrata

Snail microbiota and snail-schistosome interactions: axenic and gnotobiotic technologies

The microbiota in the intermediate snail hosts of human schistosomes can significantly affect host biology. For decades, researchers have developed axenic snails to manipulate the symbiotic microbiota. This review summarizes the characteristics of symbiotic microbes in intermediate snail hosts and describes their interactions with snails, affecting snail growth, development, and parasite transmission ability. We focus on advances in axenic and gnotobiotic technologies for studying snail-microbe interactions and exploring the role of microbiota in snail susceptibility to Schistosoma infection. We discuss the challenges related to axenic and gnotobiotic snails, possible solutions to address these challenges, and future research directions to deepen our understanding of snail-microbiota interactions, with the aim to develop microbiota-based strategies for controlling snail populations and reducing their competence in transmitting parasites.

Heat shock increases hydrogen peroxide release from circulating hemocytes of the snail Biomphalaria glabrata

Planorbid freshwater snails are important intermediate hosts for parasitic diseases caused by parasitic worms, most notably schistosomiasis. There are numerous reports of snails, specifically Biomphalaria glabrata, having compromised defences against schistosomes after being exposed to thermal stress. Environmental modifications to the defenses of schistosome transmitting snails could have negative ramifications for human disease risk in the context of climate change. Here the effects of heat shock on the production of hydrogen peroxide, a primary anti-microbial effector in many molluscs, were examined. The present findings show that heat shock increases NADPH oxidase 2 mRNA levels and hydrogen peroxide produced by snail hemocytes, and that both of these phenotypes could be reversed by an HSP-90 inhibitor. These findings indicate that snail defense systems are altered by heat shock at a molecular level in B. glabrata, and that snail immunity to many pathogens may be altered by the rapid variations in temperature that are associated with global climate change.

Neither heat pulse, nor multigenerational exposure to a modest increase in water temperature, alters the susceptibility of Guadeloupean Biomphalaria glabrata to Schistosoma mansoni infection

There are increasing concerns regarding the role global climate change will have on many vector-borne diseases. Both mathematical models and laboratory experiments suggest that schistosomiasis risk may change as a result of the effects of increasing temperatures on the planorbid snails that host schistosomes. Heat pulse/heat shock of the BS90 strain of Biomphalaria glabrata was shown to increase the rate of infection by Schistosoma mansoni, but the result was not replicable in a follow up experiment by a different lab. We characterised the susceptibility and cercarial shedding of Guadeloupean B. glabrata after infection with S. mansoni under two temperature regimes: multigenerational exposure to small increases in temperature, and extreme heat pulse events. Neither long-term, multigenerational rearing at elevated temperatures, nor transient heat pulse modified the susceptibility of Guadeloupean B. glabrata to infection (prevalence) or shedding of schistosome cercaria (intensity of infection). These findings suggest that heat pulse-induced susceptibility in snail hosts may be dependent on the strain of the snail and/or schistosome, or on some as-yet unidentified environmental co-factor.

Acute exposure to physiological doses of triiodothyronine does not induce gonadal caspase 3 activity in goldfish in vitro

Seasonally spawning fish rely on a dynamic and complex hormonal interplay to regulate cycles of gonadal development and the regression. Thyroid hormones have been shown to be a key player during gonadal development, and can regulate the activity of a number of essential reproductive hormones. Apoptosis is a vital cellular process that contributes to the hormonal control of gonadal development and regression, but the roles of thyroid hormones on gonadal apoptosis in goldfish have not been explored. The present study examines the role of acute T3 exposure on caspase 3-dependent apoptosis in dispersed goldfish gonadal tissue in vitro. We examined the levels of caspase 3 activity in early, mid, and late recrudescent gonadal tissue after exposure to physiological doses of T3 for up to 24 h. Acute treatment with T3 did not alter basal caspase 3 activity in goldfish gonads in vitro in these reproductive stages. This initial study suggests that transient increases in T3 levels are unlikely to directly contribute to basal caspase 3-dependent apoptosis in the gonadal tissue of goldfish, although we cannot rule out an interaction of T3 with other hormones involved in the control of apoptosis in the testis and ovary.

Allelic variation in a single genomic region alters the hemolymph proteome in the snail Biomphalaria glabrata

Freshwater snails are obligate intermediate hosts for numerous parasitic trematodes, most notably schistosomes. Schistosomiasis is a devastating human and veterinary illness, which is primarily controlled by limiting the transmission of these parasites from their intermediate snail hosts. Understanding how this transmission occurs, as well as the basic immunobiology of these snails may be important for controlling this disease in the future. Allelic variation in the Guadeloupe resistance complex (GRC) of Biomphalaria glabrata partially determines their susceptibility to parasitic infection, and can influence the microbiome diversity and microbial defenses in the hemolymph of these snails. In the present study, we examine the most abundant proteins present in the hemolymph of snails that are resistant or susceptible to schistosomes, as determined by their GRC genotype. Using proteomic analysis, we found that snails with different GRC genotypes have differentially abundant hemolymph proteins that are not explained by differences in transcription. There are 13 revealed hemolymph proteins that differ significantly between resistant and susceptible genotypes, nearly 40% of which are involved in immune responses. These findings build on the mounting evidence that genes in the GRC region have multiple physiological roles, and likely contribute more extensively to the general immune response than previously believed. These data also raise the intriguing possibility that the GRC region controls resistance to schistosomes, not directly, but indirectly via its effects on the snail's proteome and potentially its microbiome.