Comment »Posted on Sunday 30 May 2010 at 4:31 pm by Mia Kukathasan
In Biology, Evolution

Male crickets that grow up surrounded by the songs of many potential competitors, grow up bigger and stronger than counterparts reared in silence. It seems that the sound of masculine chirps ends up masculinising young crickets within hearing range.

Researchers from The University of California, Riverside, measured the testicular tissue mass of young male crickets that had been played cricket song, and found that they grew up to have nearly 10% more testicular mass than the youths without such auditory cues of competition. A big part of the male crickets’ mating strategy involves a long-range call. The song can be ‘parasitized’ by other males, who lurk nearby, taking credit for the masculine calls to impress arriving females. But, the males that grew up surrounded by the songs of other males were less likely to use such underhand tactics. Instead they were generally bigger, noisier and in overall better shape.

It seems mating matters to crickets, in fact so fixated are decorated crickets that they will sacrifice their health to impress the females. As part of the mating process, males offer their mates an adorably named ‘nuptial food gift’, a gummy blobby concoction that they synthesize and transfer to the females along with sperm. Scientists from Illinois State University managed to coerce some decorated crickets into producing larger food packages, which they did, despite it lowering their immune systems.

After all that effort, when the deed has been done, mating mission accomplished, there’s still no guarantee that the sperm that entered the female cricket will be the sperm that fertilises her eggs. Of course some of it will be, but with the promiscuity of female crickets, and the aggressive mating tactics of males, multiple matings with the same female are common. So, who becomes the daddy?

Researchers from Exeter university found that even after mating with up to ten males, promiscuous female field crickets can control the amount of sperm that they store from each mate, regardless of the order they mated in. Although crickets don’t avoid mating with relatives, they do reduce the chances of producing unfit inbred offspring, by using their abdominal muscles to keep hold of more of the sperm from unrelated males. Scientists from Australia and Switerland went further and found that a male’s chances of fathering “increases with its attractiveness and decreases with the size of the female”.

In the harsh world of insect reproduction, once the eggs have been laid, the little ones are on their own. Although the mothers don’t stick around, researchers at the University of South Carolina Upstate, have found that they can leave hidden maternal messages in their unborn babies, to prepare them for the harsh realities of existence. Storm and Lima (researchers, with names like comic superheros), placed pregnant crickets in enclosures with predatory wolf spiders whose fangs were tipped with wax. This meant the spiders could stalk the crickets, make them extremely frightened, but not actually kill them.

The offspring of mothers born to the spider-stalked mothers were faster to react to the danger of predators, than the control offspring from mothers kept more cushy circumstances. These offspring of ‘stalked’ mothers ran for cover more quickly and stayed in hiding for more than twice as long. They would also freeze when coming across signs of their predators, signs such as spider silk or spider faeces. Having this fear, unsurprisingly meant that they ended up with higher survival rates.

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