Frog eye change described in Journal of Experiment Biology (JEB), 21 April 2016, doi: 10.1242/jeb.141127. When animals and people move, their eyes have to compensate for the movement in order to keep a steady view of the world. Without this the world would appear to be constantly moving like a bad case of “camera shake”. This compensation is achieved by brain circuits that monitor the control signals from the nervous system to the muscles and move the eyes in a complementary way.

When tadpoles metamorphose into frogs their method of swimming changes from a fish-like wriggle to a thrust forward by the movement of their back legs. This means the compensatory eye movements have to change in order to keep their gaze steady. When they swim like a fish their eyes swivel from one side to the other with the body movement. This is controlled by brain circuits that monitor the nervous system control of the body muscles. When a frog swims the eyes have to move in and out, opposite to one another, like crossing and uncrossing the eyes, to compensate for the forward thrusting movement of the back legs.

Scientists at University of Bordeaux, France, and Ludwig-Maximilians-University Munich, Germany monitored the brain function and muscle movement of tadpoles undergoing metamorphosis into frogs. They found the eye control signals gradually changed from the swivelling to the crossing movement as brain circuits that control the movement became less attuned to the movement of the body muscles and more attuned to the control of the developing leg muscles. During metamorphosis the eyes could both swivel and cross, so that the animals experienced a seamless change from one type of movement to another.


Editorial Comment: All vertebrates, including we humans, have a system of complementary eye movements to keep our gaze steady. You can know how well it works because this editor is working on the ENEWS in a rocking train on the way to Scotland. You can also compare your experience of seeing the world when you walk and move, compared with the results you get when you walk holding a video camera, unless you have been trained to compensate for your movement while holding a camera.

Many modern digital cameras include a device that can compensate for some movement when the camera is held in your hands, rather than on a tripod. The electronic circuit that does this required creative design and engineering. The brain circuits that control eye movements are far more sophisticated and process much more information than a camera does.

To have such circuits set up so they can change from one form of movement to another during frog metamorphosis, is a reminder that the metamorphosis of amphibians requires inbuilt planning and coordination. The drastic transformation involved in changing a tadpole into a frog involves far more than just growing legs and lungs and losing a tail and gills. The whole organism must be changed in a co-ordinated way, and that involves plan and purpose, not chance evolution.

Keeping the brain circuits functioning in line with the muscle changes requires clever re-programming of its brain. If the metamorphosing frog was unable to control its eye movements in a way suitable for all stages of the process it would be unable to swim properly, or move onto land, and would be vulnerable to predators in an evolutionary struggle for existence.

In fact, the whole process of metamorphosis, with its drastic changes in body form and function makes no sense unless the whole life cycle was built into the organism from the start. A tadpole can survive quite well but cannot reproduce, but why change its body structure so radically in order to reproduce, unless it was already designed to do so by the Creator who designed the whole life cycle. (Ref. amphibians, vision, locomotion)

Evidence News vol. 16, No.8
4 May 2016
Creation Research Australia