Blurred vision for brainless jellyfish, according to an article in news@nature, 11 May 2005. Box jellyfish, or cubozoans, are cube shaped creatures that actively chase prey and swim around obstacles, unlike most jellyfish which just drift in ocean currents and eat whatever gets trapped in their tentacles. Cubozoans have an eye-stalk on each corner that contains six eyes. Four of the eyes are simple pits filled with light sensitive pigments. The other two eyes have a lens with a finely graded refractive index that enables it to focus light onto a point. This type of lens is used to produce sharp images in fish, squid and octopi, but the retina (the light sensitive layer) in the cubozoan eye is behind the point where the light is focussed, which means the image falling on the retina is blurry. Researchers at Lund University in Sweden who have been studying cubozoan eyes suggest that this is a useful feature because the jellyfish don’t have brain that can sort and filter visual information. The blurry image enables the jelly fish to find its way around large objects in its environment without being distracted by fine particles floating in the water.
Editorial Comment: These complex ponderings by highly qualified scientists remind us that eyes do not work in isolation – they must function in line with the rest of the creature and according to its needs. Therefore, it is not enough for evolutionists to speculate how an eye could form in graduated steps from simple to complex. In this case they have to explain how the cubozoan eye developed in a precise way to work without a brain, but at the same time provide the information needed for the jellyfish to navigate and find food. (Ref. design, optics, eyes)