July 2012
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| Ladybird. Kirsty Coghill [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons |
Ladybirds are predators of many small
insects, and therefore provide and important natural pest-control
service to agriculture. In 2008, Angelika Hilbeck and her colleagues
at the Swiss Federal Institute of Technology published a study on the
effects of Bt-toxins on ladybirds.
Noting that the assessments of GM crops
have attracted criticism because they're based on the those used for
chemicals, Hilbeck aimed to develop a more appropriate method.
Her team improved the protocol by using Bt toxins in activated form
(which is what Bt crops are supposed to produce) and by testing
ladybird larvae (grubs) rather than the much less vulnerable adult
insect.
Purified, activated Bt toxin was accordingly sprayed onto eggs of the flour moth, which are considered a high-quality food for ladybird-type insects. Such eggs were supplied to the developing larvae as their sole food-source for the duration of their existence.
One of the toxins tested was Bt protein
'Cry1Ab' which is generated, for example, by MON 810 maize approved
for cultivation in the EU. When this was fed to the developing
ladybirds at various concentrations, up to 44.2% of the first-stage,
newly-hatched, larvae died (compared with 14.2% of control larvae
with no exposure to the toxin). The surviving later-stage grubs
weren't further affected.
Cry1Ab is claimed to be highly specific
against moths which are a major pest in maize and cotton, and
is marketed as 'environmentally-friendly' because it isn't supposed
to kill other types of insects. Hilbeck's finding was among some 30
other studies which raised questions about the environmental effects
of MON 810 and was used by the German government to ban the crop.
The paper was, therefore, very unwelcome in biotech-circles.
What happened next is a familiar
shoot-the-messenger story. Within weeks of the damning study
appearing in print, two letters appeared in the journal Transgenic
Research. These letters amounted to a lengthy, “disrespectful”
and “unnecessarily confrontational” attack by fellow scientists.
For example, the data were referred to as “alleged” and
“supposedly showing a negative impact”*, the research was
categorised as “ill-conceived and shoddy”, and the title of one
even suggested the study was “pseudo science”. Hilbeck's team
were not offered any opportunity to respond.
Barely a year later, Transgenic
Research published a rushed study by another Swiss team led by
Fernando Alvarez-Alfageme. This succeeded in demonstrating that Bt
toxins had no adverse effects on ladybird larvae, declaring Hilbeck's
results to be “artifacts of poor study design and procedures”,
and the German decision-makers guilty of failing to evaluate the
quality of the individual scientific studies used in its
decision-making process on GM maize.
The lynch-pin of Alvarez-Alfageme's
investigation was that ladybird grubs “do not consume entire prey
items but instead puncture the prey and suck out the contents”.
Visual observations, verbally reported, indicted that no parts of the
moth egg shells were consumed, therefore the larvae “cannot be
dosed with test compounds deposited on the outside of the eggs”.
To present the ladybirds with “more realistic routes of exposure”
to the toxins, this team used a Bt-laced sugar solution in one
feeding experiment, and spider mites which had been fed on Bt maize
leaves in another.
Aware of what seemed like a concerted
attempt to discredit her research in these three publications (all
appearing in the same scientific journal), Hilbeck carried out a
further set of experiments using a further improved technique and
designed to disprove the Alvarez-Alfageme's effort.
Hilbeck first subjected European corn
borer, a pest which MON 810 maize is actually designed to
kill, to Alvarez-Alfageme's protocol. The Bt-sensitive worms were
affected only slightly or not at all. There was no need to look far
for an explanation for this discrepancy: Alvalrez-Alfageme had
exposed his ladybirds to the Bt toxin for only 24 hours, followed by
a long (in lady-bird terms) toxin-free recovery period. This aspect
of the method wasn't mentioned in the abstract.
When an attempt was made to repeat the
toxic sugar solution feeding study as described, the liquid simply
dried up rendering it unavailable to the test larvae.
No attempt was made by Hilbeck to
repeat Alvarez-Alfageme's Bt-fed spider mite feeding study. The
presence and nature of other proteins and gut microbes are known to
interact with Bt proteins and can yield unexpected effects:
introducing a layer of complexity in the form of a third
organism-species as food simply raises more questions than it can
possibly answer.
Important new data on the feeding
habits of ladybird larvae was presented in photographic form: these
grubs have short biting mouth-parts which they sink “deeply into
the eggs” afterwards “biting their way through the egg shells ...
the egg content leaks out of the eggs and the larvae lick and suck up
whatever they can get out of it”. In other words, ladybird young
are messy eaters, bound to be in contact with anything on the outside
of their food. Hilbeck went on to confirm that her larvae had in
fact ingested Bt toxin while eating the moth eggs by chemical
analysis of their bodies.
OUR COMMENT
It's unclear why the journal,
Transgenic Research, should have become a platform for this
concerted attack on science. Trangenic Research is associated
with the International Society of Transgenic Technology established
in Spain in 2006: the Society website specifies its aims as to
“encourage knowledge generation ... used for the genetic
modification of animals, in particular ... in the biology,
biomedicine and biotechnology disciplines”. The journal isn't so
restricted and publishes any type of GM research, animal, plant, or
microbes. Perhaps its access to expertise in the fields of
environmental science and toxicology are inadequate to evaluate such
submissions adequately: indeed this may be part of the bigger picture
of why GM development and its safety assessment have become so
polarized. However, since there are signs here, the Transgenic
Research is being used by the pro-biotech lobby for political
ends, it might be worth remembering the name: it might well crop up
again next time someone publishes GM-unfriendly results.
The most interesting thing to come out
of all this is how little is known about the environmental
interactions of any Bt toxin, and that “even in target pests the
mode of action of Bt toxins is not fully understood” (Schmidt).
All these warring scientists did
agree on one thing: Bt toxins generated in GM plants end up inside
the animals living on and around them (including humans). So, what
happens when you stack up six different Bt toxins in the same plant,
like Monsanto's super-duper insect-killing GM maize machine,
'SmartStax'?
If you're wondering about the increased
presence of ladybirds recorded in Bt cotton fields in China (see
APHID-FRIENDLY COTTON - July 2012), this crop generates a
different Bt protein from the one tested by Hilbeck. However, the
next generation of GM cotton there will likely have Cry1Ab stacked on
top of what it has now, and Chinese ladybirds might be cut off in
their prime.
If the name 'Ricroch' seems familiar,
this is the same French scientists who cobbled together a review of
long-term and multigenerational GM feeding studies in 2011. The
timing and nature of this review looked suspiciously like a
counter-attack on other scientists whose earlier reviews had not been
favourable towards GM. Check out THREE REVIEWS OF GM SAFETY - March 2012.
Remember these stories. If GM was safe
to eat and safe for the environment, scientists would be able to
prove it without resorting to ungentlemanly behaviour.
SOURCES:
- Jörg E. U. Schmidt et al., 2009, Effects of Activated Bt Transgene Products (Cry1Ab, Dry3Bb) on Immature Stages of the Ladybird Adalia bipunctata in Laboratory Ecotoxicity Testing, Archives of Environmental Contamination Toxicology, 56
- Lethal Effects of Genetically Modified Bt Toxin Confirmed On Young Ladybird Larvae, www.sciencedaily.com, 27.02.12
- Bt Toxicity Confirmed: Flawed Studies Exposed, Institute of Science in Society Report 11.07.12
- Agnès Ricroch et al., 2010, Is the German suspension of MON810 maize cultivation scientifically justified?, Transgenic Research 19
- Stefan Rauschen, 2010, A case of “pseudo science”? A study claiming effects of the Cry1Ab protein on larvae of the two-spotted ladybird is reminiscent of the case of the green lacewing, Transgenic Research 19
- Fernanado Alvarez-Alfageme et al., 2011, Laboratory toxicity studies demonstrate no adverse effects of Cry1Ab and Cry3Bb1 to larvae of Adalia bipunctata coleoptera Coccinellidae): the importance of study design, Transgenic Research, 20
- Angelika Hilbeck et al., 2012, A controversy re-visited: is the coccinellid Adalia bipunctata adversely affected by Bt toxins?, Environmental Sciences Europe, 24:10
- Angelika Hilbeck et al., 2012, Underlying reasons of the controversy over adverse effects of Bt toxins on lady beetle and lacewing larvae, Environmental Sciences Europe, 24:9
- Snell Chelsea et al., 2011, Assessment of the health impact of Gm plant diets in long-term and multigenerational animal feeding trials: A literature review, Food Chemical Toxicology
- International Society for Transgenic Technologies, www.transtechsociety.org
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