(HOST) Lightening bugs offer an impressive display this time of year, but commentator Ruth Page says another little beetle can actually choose to light up either of two colors, yellowy-green or bright orange, to announce its presence to potential mates.
(PAGE) Bugs, as we all now realize, do the darnedest things. Some dig (there are even some little bees in the American south- west that do so). Some, like the useful dung beetles, eat dung, thus saving us from a fate worse than death. Some eat dead crea- tures like the now rare burying beetle, and many others, such as bees that pollinate our crops, are essential to human health and comfort.
Recently, I read of one that may not be useful to us, but is so unusual it’s irresistible. It doesn’t only glow with color – which isn’t too rare in nature – but, like an artist, can create different colors with different organs.
It’s the Jamaican click beetle, and it’s the only bioluminescent creature that can do so; it’s unique on earth so far as is known. Care to attempt its name, which is rather longer than the beetle? It’s Pyrophorus plagiophthalamus. It has a pair of light organs on its back that can produce yellow-green or green light, and a pair on its belly that can glow yellow-green or orange.
With the patience of Job and true scientists, a biologist formerly
at the University of Notre Dame and his colleagues have learned which gene the belly organ “turns on” or activates to make luci- ferase, the enzyme that allows creatures to emit light.
What they don’t know is what caused the evolutionary change that led to the shift toward orange light. The change was in the lucifer- ase, but why? As they do so often, the researchers think it’s sex, always first among the usual suspects. Perhaps choice of color helps the beetles attract mates. That’s just a guess, though pro- bably a good one. Sex, with its ability to pass on one’s genes to off-spring, is a common reason for new adaptations.
During mating season the male beetles fly overhead, just as light- ning bugs do, to signal to mates below. Pyrophorus males use their belly lights, of course, to signal downward. Females that are attracted to them turn on their back lights to signal a response. It appears that nowadays the fellas that glow orange are getting the go-ahead light from below more often than do those that stick with the old yellow-green glows.
The scientific article published about this curious discovery had a very precise, descriptive, title: “Darwinian natural selection for orange bioluminescent color in a Jamaican click beetle”. The paper first appeared in December 2003.
This is Ruth Page, once again expressing surprise at the accomp- lishments of tiny creatures and their intricate responses to environ- mental changes.