AChE as a biomarker to detect sub- lethal impacts of neonicoinoids on honeybees.

Transcription

1 AChE as a biomarker to detect sub- lethal impacts of neonicoinoids on honeybees.. Madeleine Chagnon Ph.D. Environmental sciences Assistant Professor at Université du Québec à Montréal Associated researcher at Centre de recherche en sciences animales de Deschambault Monique Boily, Ph.D. Environmental sciences Assistant Professor at Université du Québec à Montréal Symposium: The Canadian Pollina4on Ini4a4ve Guelph, Ontario 23 October 2013 Monique Boily, Benoit Sarrasin, ChrisIan Deblois, Philippe Aras & Madeleine Chagnon (2013). Ache as a biomarker to detect sub- lethal impacts of neonicoinoids on honeybees acetylcholinesterase in honey bees (apis mellifera) exposed to neonicoinoids, atrazine and glyphosate: laboratory and field experiments. Environmental Science and Pollu2on Research.

2 Acetylcholinesterase ( AChE) is an enzyme that degrades the neurotransmiter acetylcholine. What we already knew: Decrease in AChE is an indicator of exposure to organophosphorus or carbamate pesicides. NeonicoInoids and their metabolites are agonists of acetylcholine (Nauen et al. 2001). They bind to the post- synapic nicoinic receptors nachers triggering a coninuous signal leading to the death of the insect. Their high efficiency is atributed to the irreversible link with the nachers receptors Consequently, AChE acivity was evaluated as a biomarker for exposure to neonicoinoid pesicides.

3 Laboratory and Field trials

4 Laboratory trials Honey bees were taken on frames without brood from a healthy beehive Placed in acrylic cages (13 X 14 x 18 cm) in groups of 30. Maintained in a temperature- controlled room (darkness, 25±1 C with 55±5 % relaive humidity). Four replicates for each treatment. Fed (50 % s/w) ad libitum for 24 h before experiment

5 Laboratory trials The lowest exposure levels were based on analyzed in- field pollen and nectar concentraions (BonmaIn et al. 2005; Chauzat et al. 2006) in order to represent field- realisic exposures. Bees were offered 1: 2 sugar soluions spiked with nominal concentraions of imidacloprid (0.08, 0.16, 0.24, 0.30 ng per bee) clothianidin (0.03, 0.06, 0.12 and 0.24 ng per bee) Oral LD50 = ug a.i./bee.

6 Field trials Two regions In maize fields, foraging bees are exposed to residual concentraions of insecicides such as neonicoinoids used for seed coaing. In Québec, coated seeds count for more than 99 % of maize crops and 30 % to 50 % of soya crops (Giroux and PelleIer 2012).

7 At the same Ime, approximately 30 to 40 acive foragers were captured in front of each hive, using a collector s net Field trials In each region, three field condiion, were tested : 1. organically grown maize, 2. convenionally grown maize and 3. non- culivated fields (situated at least 3 km away from any crop using coated seeds). A total of 18 honey bee colonies (3 hives per condiion X 3 condiions X 2 regions) All colonies were equalized in brood surface (larvae) and bee populaion before the beginning of the experiment. The hives were placed a few days before maize pollen shedding, from August 5 to September 5 (2009) One hive per field was equipped with a pollen trap. Once a week, all colonies were checked for diseases and pests Mortality was assessed by couning the number of dead bees accumulated on a 1 X 1 m white sheet placed in front of the hive.

8 Heads of honeybees were homogenised for use by a micro plate method and measures with colorimeters. 8 to 10 heads were use for one analysis. From 5 to 15 replicates were made for each sample. Were compared AChE acivity umol/h/g Issue AChE acivity umol/h/per gr protein Protein concentraion mg/g Bee weight g

9 Pollen in traps were hand sorted Percentage of maize pollen was recorded Pellets were idenified on microscope slides

10 RESULTS FROM LABORATORY TRIALS Effects of chronic exposure (10 days) of imidacloprid on honey bee s survival and hyperac4vity. a Survival. Values represent the cumulated number of events (death) of four replicates (cages) per dose and the control group X 100. Survival for each dose was compared to the control group using χ2 test. b. Hyperac4vity. Values represent the cumulated behaviour observaions (tumbling and trembling) of four replicates (cages) per dose X 100 HyperacIvity was compared to the control group using Fisher s exact test

11 RESULTS FROM LABORATORY TRIALS

12 RESULTS FROM FEILD TRIALS Organic ConvenIonal maize fields nonculivatedfields

13 FEILD RESULTS It is possible that the higher AChE acivity found in bees during week 2 corresponded with the maize pollen emission peak. Maize pollen may contain residual concentraion of pesicides, e.g. imidacloprid: 2 to 3 ng/g (BonmaIn et al. 2005),

14 In the field study, honeybees were exposed to a NeonicoInoid pesicide (Clothianidin or Thiamethoxam), probably at very low doses. This was probably not the only pesicides that they were. potenially exposed to. The fact that AChE acivity was not found to be inhibited shows that Carbamates or Organophosphorus pesicides were not the cause of observed honeybee mortality.

15 Many laboratory experiments have been conducted to test the toxicity of neonicoinoids on honey bees. To our knowledge, this is the first Ime that an increased AChE acivity is reported for both in- field and laboratory data implicaing. honey bees. Honeybees from colonies with high mortality showed similar abnormality in biomarkers as those feed pesicides in experimental cages while honeybees from healthy hive were comparable to those from the control cages..

16 Thank you Philippe Aras Arnaud Villier Isabelle Ferland Stéphane Laramée André Pepgrew Émile Houle Geneviève Beaunoyer Dieynaba Diop Hannan Alami François Gouin Legault Mikael Benoit