Comparison of the toxic effects of two duncecap larkspur (Delphinium occidentale) chemotypes in mice and cattle.
ABSTRACT To compare the toxic effects of a Delphinium occidentale chemotype containing N-(methylsuccinimido) anthranoyllycoctonine (MSAL)-type alkaloids and a D occidentale chemotype lacking MSAL-type alkaloids in mice and cattle.
225 male Swiss Webster mice and 11 Black Angus steers.
4 collections of larkspur containing MSAL-type alkaloids and 4 collections of larkspur lacking MSAL-type alkaloids were used. From each collection, total alkaloid extracts (0.05 to 0.20 mL) were administered via tail-vein injection in 27 to 29 mice. Dried, finely ground plant material from 1 collection with and 1 collection without MSAL-type alkaloids (doses equivalent to 37.6 mg of total alkaloids/kg) were each administered to 8 cattle via oral gavage in a crossover experiment; 3 cattle received a single dose equivalent to 150.4 mg of total alkaloids/kg (no MSAL-type alkaloids). In mice, clinical effects were monitored; in cattle, heart rate was monitored before (baseline) and 24 hours after treatment. At the 24-hour time point, cattle were exercised as a measure of muscle weakness.
In mice, mean LD(50) associated with alkaloid extracts prepared from plants that did or did not contain MSAL-type alkaloids was 2.3 and 54.2 mg/kg, respectively. In cattle at 24 hours after treatment, plant material containing MSAL-type alkaloids significantly increased heart rate from baseline and was associated with exercise-induced collapse; plant material lacking MSAL-type alkaloids had no similar effects.
Taxonomic classification of D occidentale alone was not a good indicator of the toxic risk to grazing cattle.
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ABSTRACT: Although secondary metabolites are prevalent in floral nectar, the ecological consequences for pollinators and pollination remain relatively unexplored. While often deterrent to pollinators at high concentrations, secondary metabolite concentrations in nectar tend to be much lower than secondary metabolite concentrations in leaves and flowers; yet, they may still affect the maintenance of pollination mutualisms.Delphinium barbeyi, a common montane herb, contains norditerpene alkaloids in its nectar but at concentrations that are substantially lower than those found in its leaves or flowers. By manipulating nectar alkaloid concentrations in the field and laboratory, we assessed the degree to which varying concentrations of alkaloids in nectar influenced pollinator behaviour and activity and plant reproduction.In the field, nectar alkaloids significantly reduced both the number of flower visits and the time spent per flower by free-flying bumblebee pollinators, but we only observed effects at alkaloid concentrations 50 times that of natural nectar. When we supplemented D. barbeyi nectar with alkaloids at concentrations almost 15 times that of natural nectar, we found no evidence for direct or pollinator-mediated indirect effects on female plant reproduction.In the laboratory, the direct consumptive effects of nectar alkaloids on bumblebee pollinators were also concentration dependent. Bumblebees exhibited reduced mobility and vigour but only at alkaloid concentrations more than 25 times higher than those found in natural nectar.Synthesis. We found that nectar alkaloids have dose-dependent effects on pollinator behaviour and activity. While concentrations of nectar alkaloids rivalling those found in leaves would negatively affect pollinator behaviour and pollination services, the natural concentrations of nectar alkaloids in D. barbeyi have no negative direct or pollinator-mediated indirect effects on plant reproduction. These results provide experimental insight into the dose-dependent ecological consequences of nectar secondary metabolites for pollinators and pollination, suggesting that low nectar alkaloid concentrations incurred no ecological costs for D. barbeyi.Journal of Ecology 11/2013; 101(6). · 5.69 Impact Factor
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ABSTRACT: Microorganisms frequently colonize the nectar of angiosperm species. Though capable of altering a suite of traits important for pollinator attraction, few studies exist that test the degree to which they mediate pollinator foraging behavior. The objective of our study was to fill this gap by assessing the abundance and diversity of yeasts associated with the perennial larkspur Delphinium barbeyi (Ranunculaceae) and testing whether their presence affected components of pollinator foraging behavior. Yeasts frequently colonized D. barbeyi nectar, populating 54-77% of flowers examined depending on site. Though common, the yeast community was species-poor, represented by a single species, Metschnikowia reukaufii. Female-phase flowers of D. barbeyi were more likely to have higher densities of yeasts in comparison to male-phase flowers. Pollinators were likely vectors of yeasts, as virgin (unvisited) flowers rarely contained yeasts compared to flowers open to pollinator visitation, which were frequently colonized. Finally, pollinators responded positively to the presence of yeasts. Bombus foragers both visited and probed more flowers inoculated with yeasts in comparison to uninoculated controls. Taken together, our results suggest that variation in the occurrence and density of nectar-inhabiting yeasts have the potential to alter components of pollinator foraging behavior linked to pollen transfer and plant fitness.PLoS ONE 10/2014; 9(10):e108214. · 3.53 Impact Factor
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ABSTRACT: Low larkspurs have different toxic potentials to livestock due to variation in the individual alkaloids present in the plants. Two species, Delphinium nuttallianum and Delphinium andersonii were dosed to 10 Holstein steers at 10mg and 12mg toxic alkaloids/kg, respectively. Blood samples were collected periodically for 96h, analyzed for serum alkaloid concentrations and toxicokinetic parameters calculated for 16-deacetylgeyerline, 14-deacetylnudicauline, methyllycaconitine and geyerline/nudicauline which co-eluted in the serum analysis. The maximum serum alkaloid concentrations and area under the curve values for 16-deacetylgeyerline and geyerline/nudicauline were significantly different between the two groups due to the concentrations of the alkaloids in each larkspur species. The alkaloid elimination half-lives were similar for the two larkspur species. These results suggest the elimination rates of norditerpene alkaloids from different larkspur species in cattle are similar regardless of plant alkaloid composition. The determining factor for larkspur toxicity is the individual alkaloid composition of the plant.Research in Veterinary Science 05/2013; · 1.51 Impact Factor