This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers at the Francis Crick Institute have identified a specialized lipid barrier in the fruit fly pupa that protects against dehydration in dry and hot environments. Their findings also expose the lipid barrier's limit, suggesting that insects in some regions of the world may struggle to adapt to climate change.
The fruit fly, or Drosophila, is widely used in research and can provide insights into how insects protect themselves from environmental stresses. Drosophila spends its early days as a larva in a humid environment, feeding and burrowing in decomposing fruit. It then crawls to a drier place and becomes an immobile pupa.
The pupa develops into an adult fly through a complex transformation called metamorphosis. The pupal and adult stages of insects like Drosophila occupy dry-land environments and are therefore particularly vulnerable to dehydration. To help prevent this, the adult fruit fly is covered with a barrier of lipid (fat): a hydrophobic coating made of long hydrocarbon molecules that blocks water loss.
Until now, researchers didn't know how the pupa protects itself from dehydration or what kind of hydrocarbon barrier it might have. As many of the known hydrocarbons in Drosophila are similar to those found in crude oil, the team at the Crick analyzed them by adapting methods from the petroleum industry and by using state-of-the-art molecular imaging. Published in Science Advances, these findings revealed a surprise: the pupa doesn't have any hydrocarbons on the surface of its outer body casing (cuticle), whereas the adult has them in abundance.
Instead, the pupa's lipid barrier is internal, coating the underside of the cuticle, and it is made of hyper-long hydrocarbons, much longer than those of the adult. Next, the team traced the origin of the hyper-long hydrocarbons, finding that they are premade by specialized cells in the larva and then stored until needed in the larva's fat reserve. The researchers think that this anticipatory strategy may allow hyper-long hydrocarbons to be deployed very quickly to the underside of the cuticle during the rapid transition from larva to pupa.
By looking at the expression of genes involved in producing hydrocarbons, the team identified a specific elongase enzyme that makes hyper-long hydrocarbons. However, removing this enzyme in standard laboratory conditions didn't have a huge impact, suggesting that other elongase enzymes also contribute to the production of hyper-long hydrocarbons. The researchers then recreated high-temperature and low-humidity conditions, similar to those of some subtropical and Mediterranean climates.
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