Pesticides reduce pollination

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Close-up of a bee with pollen flying by a flower. Credit: Jon Sullivan. License: PD

Bees have difficult times these days, what with that mysterious colony collapse disorder on top of various viral, bacterial and parasitical diseases. Of course, the widespread use of pesticides did not help the thriving of the hive, as many pesticides have various deleterious effects on the bees, from poor foraging or less reproduction to even death.

The relatively new (’90s) class of insecticide – the neonicotinoids – has been met with great hope because has low toxic effects on birds and mammals, as opposed to the organophosphates, for example. Why that should be the case, is a mystery for me, because the neonicotinoids bind to the nicotinic receptors present in both peripheral and central nervous system in an irreversible manner, which does not put the neonicotinoids in a favorable light.

Now Stanley et al. (2015) have found that exposure to the neonicotinoid thiamethoxam reduces the pollination provided by the bumblebees to apples. They checked it using 24 bumblebee colonies and the exposure was at low levels over 13 days, trying to mimic realistic in-field exposure. The apples visited by the bumblebees exposed to insecticide had 36% reduction in apple seeds.

Almost 90% of the flowering plants need pollination to reproduce, so any threat to pollination can cause serious problems. Over the paste few years, virtually all USA corn had been treated with neonicotinoids; EU banned the thiamethoxam use in 2013. And, to make matters worse, neonicotinoids are but only one class of the many toxins affecting the bees.

Related post: Golf & Grapes OR Grandkids (but not both!)

Reference: Stanley DA, Garratt MP, Wickens JB, Wickens VJ, Potts SG, & Raine NE. (Epub 18 Nov 2015). Neonicotinoid pesticide exposure impairs crop pollination services provided by bumblebees. Nature, doi: 10.1038/nature16167. Article

By Neuronicus, 21 November 2015

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Golf & Grapes OR Grandkids (but not both!)

Pesticides may be bad for you, but they are devastating for your great grandchildren, because there will be no great great grandchildren. Photo Credit: JetsandZeppelins from Flickr under CC BY 2.0 license
Pesticides may be bad for you, but they are devastating for your great grandchildren, because there will be no great great grandchildren. Photo Credit: JetsandZeppelins from Flickr under CC BY 2.0 license

Transgenerational epigenetic inheritance (TGI) refers to the inheritance of a trait from one generation to another without altering the DNA code (normally, evolution is driven by changes in the DNA itself). Instead, it happens by modifying the proteins that wrap around the DNA, the histones; these histones, in turn, control what genes will be expressed and when. Until a decade ago, TGI was considered impossible, nay, a scientific heresy since it had too close of a resemblance to Lamarckian evolution. But, true to its guiding principles, the scientific endeavor had to bite the bullet in front of amassing evidence and accept the fact that it may have been a kernel of truth to the so called ‘soft inheritance’.

Anway et al.’s paper was one of the first to promote the concept, ten years ago. They exposed pregnant rats to the pesticides vinclozolin or methoxychlor (only vinclozolin is still used widely in U.S.A. and several EU countries, particularly in agriculture, wine production, and turf maintenance; methoxychlor was banned in the early noughts). The authors found out that more than 90% of the male offspring had “increased incidence of male infertility”. These effects were transferred through the male germ line to nearly all males of all subsequent generations examined” up to great great grandsons, inclusively (Anway et al., 2005). (I don’t want to speculate how they managed to breed the low fertility males…). That doesn’t mean that the F5 generation was OK (the great great great gransons); it means that they stopped investigating after the F4 generation (or they couldn’t breed the F4s). Moreover, the mechanism of inheritance seems to be altered methylation of the DNA histones of the male germline, and not alteration of the DNA itself. Females were affected too, but they didn’t have enough data on that experiment (the Ph.D. student that did the work had to graduate sometime…).

Although the authors used higher amounts of pesticides than they suspected back then, in 2005, to be found in the environment, the study still gives pause for thought. After all, it has been 10 years since this paper plus the previous 20 years of use of the stuff. And no, you cannot get rid of it by washing your grapes and vegetables really thoroughly.

Reference: Anway, M. D., Cupp, A. S., Uzumcu, M., & Skinner, M. K. (3 June 2005). Epigenetic transgenerational actions of endocrine disruptors and male fertility. Science, 308(5727): 1466-1469. DOI:10.1126/science.1108190. Article + Science Cover + FREE PDF

by Neuronicus, 25 September 2015