Insects use antibacterial secretions to protect young

Burying beetle Without the anti-bacterial secretions, the beetle's young fail to gain weight and die

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Scientists have confirmed that so-called burying beetles coat their young's food with an antibacterial substance to guarantee their survival.

Burying beetles lay their eggs on the carcasses of small animals, such as birds and rodents.

The researchers show that without the anti-microbial secretions the young fail to gain weight and die.

The results were presented the 13th Congress of the European Society for Evolutionary Biology.

Most animals try to do the best for their young, but burying beetles, in the genus Nicrophorus, which are found in temperate regions in Europe and North America, are truly doting parents.

As a prospective parent, burying beetles find a dead animal, such as a mouse or bird, and roll the carcass into a ball.

They then bury the carcass, hiding it from predators that might eat it or fancy it for a nursery for their own young - no small feat for a beetle that is only 15mm long.

The beetles then lay their eggs in the flesh of the animal and wait to welcome their young into the world.

But a buried carcass is not going to stay fresh for very long, and the bacterial communities that colonise it are likely to threaten the beetle's developing larvae.

Germ-free

So burying beetles use secretions from their anal glands to coat the fur or feathers with substances that guarantee the carcass stays germ-free and fresh for longer.

Now scientists from the University of Manchester have worked out what makes these secretions so good at killing germs.

The researchers extracted secretions from the anal glands of a species of burying beetle called Nicrophorus vespilloides, and showed that when this substance was added to bacterial cells, they were destroyed.

Evolutionary biologists Andres Arce, who led the study, and his colleagues, suspecting that they were dealing with a enzyme that "chops up microbial cell walls", investigated and confirmed that the secretions were rich in lysozymes.

These are anti-microbial enzymes, and a common component of animals' immune systems.

Lysozymes are also secreted in mammals' breast milk and in human tears.

The team showed that larva raised in the absence of either their parents secretions were 40% more likely to die before adulthood.

Dr Arce explained that for a non-social insect, these burying beetles are already known to show quite substantial levels of parental care.

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