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How does the impermeable protection of insects develop?

Insects are highly susceptible to dehydration, against which they protect themselves thanks to a thin, impermeable layer of hydrocarbons.  The mechanism underlying the formation of this coating has been revealed by an INRA team, and may be very similar from one insect to another.

Grasshopper. © INRA, Christian Slagmulder
By Clément Delorme, translated by Vicky Hawken
Updated on 08/13/2013
Published on 07/22/2013

In both summer and winter, insects tend to lose water from their bodies at a considerable rate.  This desiccation phenomenon is due to a very high surface/volume ratio, which favours dehydration.  But hexapods have found a means of avoiding such fatal desiccation.  They are coated with a thin layer of impermeable hydrocarbons which prevent the escape of water from their bodies.

A key enzyme: CYP4G

Although the existence of this hydrocarbon protection was already well known in all insects, the mechanism underlying its formation had never previously been elucidated.  This has now been achieved with the publication in PNAS (1) in September 2012 of the findings of studies by INRA researchers. Working in collaboration with colleagues at Université Paris Sud and the University of Nevada, a team from Institut Sophia Agrobiotech managed to identify the enzyme responsible for the synthesis of these protective hydrocarbons: CYP4G.

Active within large, specialised cells called oenocytes, situated on the surface of the insect,  CYP4G is indeed capable of great things.  Using long-chain aldehydes arising from fatty acids (which are available in large quantities in all living organisms), it is capable of producing alkanes or alkenes, the important molecules that render the insects impermeable. To do this, the enzyme triggers the rupture of a carbon-carbon bond at the end of the chain (a chemical reaction called decarbonylation) which is normally very difficult to achieve.

A turning point in insect evolution

Even more interesting is the fact that this mechanism may be almost the same in all insects, despite their considerable diversity.  This factor has led the scientists to think that formation of the hydrocarbon layer in insects marked one of the turning points in evolution of the largest group of organisms present on Earth.  This evolution may constitute the biochemical innovation that enabled insects to distinguish themselves from their ancestor crustaceans, and thus conquer terrestrial environments.

In the longer term, this discovery may open the way to new families of insecticides that could target the type of CYP4G enzyme that is specific to each pest that must be controlled.  Indeed, any molecule that is likely to fix the enzyme, and thus block its activity, would deprive the hexapod of its protective cuticle, leading to certain death due to dehydration.

Another prospect is to obtain biofuels from fatty acids.  By controlling the functioning of this enzyme, it would become possible to run our engines using plant-based hydrocarbons that at present cannot be used to manufacture petrol (2).

(1) Proceedings of the National Academy of Science of the United States of America.
(2) Petrol is a mixture of hydrocarbons, including alkanes and alkenes.  At present, the only hydrocarbons we know how to produce from plants are biodiesel and ethanol.

Scientific contact(s):

Associated Division(s):
Plant Health and Environment, Environment and Agronomy
Associated Centre(s):
Provence-Alpes-Côte d'Azur


Yue Qiu, Claus Tittiger, Claude Wicker-Thomas, Gaëlle Le Goff, Sharon Young, Eric Wajnberg, Thierry Fricaux, Nathalie Taquet, Gary J. Blomquist and René Feyereisen. 2012. An insect-specific P450 oxidative decarbonylase for cuticular hydrocarbon biosynthesis. Proceedings of the National Academy of Sciences of the United States of America. Sep 11;109(37):14858-63. doi:10.1073/pnas.1208650109.