Increased response to cadmium and Bacillus thuringiensis maize toxicity in the snail Helix aspersa infected by the nematode Phasmarhabditis hermaphrodita

Abstract

To determine the effect of nematode infection on the response of snails to selected toxins, we infected Helix aspersa with 0-, 0.25-, 1-, or 4-fold the recommended field dose of a commercial nematode application for agricultural use. In the first experiment, the snails also were exposed to cadmium via food and soil at concentrations of 0, 30, 60, 120, or 240 mg/kg in a full-factorial design. In the second experiment, snails were infected with nematodes and also fed either Bt (expressing Bacillus thuringiensis toxin) maize or non-Bt maize. The snails were weighed at the beginning and end (after four weeks) of the experiments, and mortality was checked daily. Neither exposure of snails to nematodes nor exposure of snails to cadmium or Bt toxin affected the survival rates of snails. The number of dead snails was highest for combinations of nematode treatments with cadmium concentrations of 120 and 240 mg/kg. In both experiments (Bt and cadmium), the growth rate decreased with increasing nematode dose. The Bt maize was not harmful to the snails in the absence of nematodes, but infected snails grew faster when fed non-Bt maize. The growth rate of snails exposed to cadmium decreased with exposure to increasing Cd concentrations and differed significantly between the no-nematode treatment and the treatments with nematode doses of one- and fourfold the recommended field dose. Snails treated with the highest dose of nematodes accumulated the highest cadmium concentrations.

Possible health impacts of Bt toxins and residues from spraying with complementary herbicides in genetically engineered soybeans and risk assessment as performed by the European Food Safety Authority EFSA

“…There are several publications pointing out that Bt proteins are highly likely to show synergies and interactions with other stressors and plant enzymes (for overview see [20]). For example, it is known that co-stressors, such as cadmium and nematodes, can cause toxicity of Cry toxins in slugs [21, 22], which can be taken as a relevant model organism. These experiments are of general relevance for risk assessment since they show that even organisms that are not known to be susceptible to Cry proteins can be impacted if exposed to other stress factors.…”

“…Thus, the combinatorial effects between the effects of glyphosate and the Bt toxins need to be assessed in more detail. For example, Kramarz et al [21] show interaction with co-stressors can render toxicity of Bt proteins to organisms that are not susceptible to Bt toxins alone. In addition, Bøhn et al [85] show that additive effects of several Cry toxins and Cry toxins interact with Roundup/glyphosate when co-exposed.…”

A controversy re-visited: Is the coccinellid Adalia bipunctata adversely affected by Bt toxins?

“…There is no reason to believe that such microbe, matrix, and toxin interactions do not apply to insects of higher trophic levels, too. Kramarz et al [43] found that nematode-infected snails grew significantly slower when raised on Bt maize compared to its non-Bt maize. Van Frankenhuyzen [44] recently reported that there are an increasing number of Bt toxin families with cross-order activity.…”

Specificity and Combinatorial Effects of Bacillus Thuringiensis Cry Toxins in the Context of GMO Environmental Risk Assessment

“…When studying the singular effect of microbially produced, activated Cry toxin Cry1Ab or via Cry1Ab producing GM maize in snails (Helix aspera), Kramarz et al (2007a) found no negative effect on H. aspersa during the observed life stages. However, when snails were infected with nematodes, the growth of the snails was significantly slower than when fed control maize (Kramarz et al, 2007b). The authors concluded that "long-term exposure is needed to reveal an effect of Bt maize.…”