Saturday, March 10, 2012

Twenty- four eyed jellyfish

Time for a boring post, everyone. They're my specialty.


This may seem rather pathetic, but for a blob of gelatin with no brain it's actually pretty impressive.


"Box jellies are the Lamborghinis of the jellyfish world. While their better-known brethren—the true jellyfish—often just drift on ocean currents with slowly undulating bells, box jellies have a need for speed. These four-sided jellies, called cubozoans, not only dart about but can spin on a dime, executing 180ยบ turns and careening around obstacles. Dr. Anders Garm of Lund University in Sweden and his colleagues wondered how these simple-looking creatures avoided slamming into objects in their paths. The answer turned out to be straightforward enough—the jellies use their eyes. Garm presented his findings at the Society of Experimental Biology's Annual Meeting (2007) in Glasgow.
Surprisingly, these translucent animals with no central nervous system to speak of are actually quite well endowed in the vision department. Biologists have long known that box jellies possess not just one or two but 24 eyes clustered on four "sensory clubs," one on each side of their bells.
For the most part, these eyes are uncomplicated organs—just a slit or a pit with some photoreceptor cells and a smudge of pigment inside. In the last few years, however, it became clear that the optics of two sets of the eyes approach the sophistication of those of higher animals. Box jellies may lack a central brain to do the processing, but they do have corneas, retinas, and fishlike spherical lenses that form images.
Even with this information, it was unclear what the jellies needed to see with such a fancy apparatus. Some have suggested that these formidable predators need eyes to chase down fast-moving prey, but many Cubozoans also live in complex habitats. Garm tested the reactions of Tripedalia cystophora, a cubozoan denizen of Caribbean swamps, to objects in its path. It turns out the jelly's lower set of camera eyes make it keenly aware of vertical barriers, presumably an important skill when swerving to avoid mangrove roots in the gloom.
Garm compared T. cystophora to an Australian cubozoan that only has to skirt large rocks and tree stumps in its natural habitat. It also perceives contrast between light intensities but can't see quite as well. Both jellies are utterly color-blind, however, so neither will be stopping for red lights on their underwater raceways any time soon." 
                                                              - Article and Image from Access Science

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