Monday, 30 July 2012

Big horned rhinoceros beetles are healthiest


The size of a male rhinoceros beetle's horn is a genuine indicator of its health, according to researchers.
The horns vary in size from small bumps to two-thirds of the insect's body length and are used in fights.
Investigating the variation, US scientists found cells in the horn are more sensitive to "nutrition signals" than cells in other parts of the body.
They suggest their findings could explain the evolution of super-sized body parts in the natural world.
The study, led by Dr Douglas Emlen from the University of Montana, US, is published in the journal Science.
Although scientists have long assumed that exaggerated body parts accurately represent the ability of a male to survive and reproduce, the link has not been proven.
To understand the relationship, Dr Emlen and colleagues compared the beetle's horn with other body parts including the wings and genitalia.
They found that the horn's cells were much more sensitive to "nutrition signals": fluctuations in insulin due to diet quality and resistance to illness.
This discovery explained the differences in horn sizes between high and low quality males but it also offered an explanation of how the horns grow to such impressive sizes.
Dr Emlen explained that these insulin pathways are also known to regulate tissue growth and body size. Therefore if a body part contains cells that are more sensitive to these signals it will grow to reflect the health of the beetle.

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