“(BBC, 26 April 2012) Tiny sharks in South East Asia have helped scientists to understand the origins of glowing shark species.
A number of deep-dwelling sharks have special light-emitting organs on their undersides that allow them to glow.
A study of pygmy sharks now suggests the ability to control the trick evolved from a shallow water ancestor.
Dr Julien Claes from the Catholic University of Louvain in Belgium led the research.
He said: "bioluminescence remains one of the most mysterious areas of shark biology."
The findings are published in the Journal of Experimental Biology.
According to Dr Claes more than 10% of currently described shark species are luminous.
Scientists refer to the glow as "counter-illumination": without it, anything looking upwards for a meal would easily see the sharks' bodies silhouetted against the bright sky above.
Previous studies have shown that lantern sharks, named for their glow, also use this ability to communicate.
By producing a hormone called prolactin, the sharks can exhibit bursts of blue light, which they use to communicate with others in dark water, where visual clues are minimal…”