Box jellyfish, which have no brain and only a basic nervous system, are enjoying newfound evolutionary status with research revealing they have surprisingly sophisticated eyes.
And it appears Australian jellyfish may have the most sophisticated visual systems of all.
Researchers from Lund University in Sweden studied a small Caribbean species of jellyfish, Tripedalia cystophora, found in mangrove swamps in Puerto Rico.
They report in today's issue of the journal Nature that the jellyfish boast impressive optical apparatus: a total of 24 eyes clustered at each of the creature's four corners.
While 16 eyes are simple 'pigment pits' to collect light, the remaining eight, a pair in each eye cluster, have complex lenses.
Despite this complexity the position of the retinas means the images the jellyfish receive are blurred.
But researchers believe the sophisticated optical set-up is designed to give jellyfish a wide field of vision to help them navigate, rather than to focus on prey.
Sophisticated stingers
"This research is groundbreaking. It really drives jellyfish up the evolutionary tree," says Dr Jamie Seymour, director of the Tropical Australian Stinger Research Unit at James Cook University in Queensland.
While he says all species of box jellyfish have a visual system similar in structure, Australian box jellyfish appear to have the most sophisticated eyes of all.
Seymour says recent research conducted in the waters of Far North Queensland by Dr Dan Nilsson from the Swedish research team suggests that Australian jellyfish can see "pretty much across the entire light spectrum".
He says their vision even appears to outdo that of birds, who are at the top of the 'visual' ladder.
"Having said that, they are not capable of producing nice crisp images because the images are actually focussed behind the retina, which causes them to blur."
Needing to see
Seymour says Australian box jellyfish need superior vision "because they are active, visual hunters" compared to the Caribbean variety that live in murky waters and fed primarily on plankton.
These Caribbean species use their vision mainly to position themselves in one spot in water currents to receive their food.
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