Octopuses feel the light, according to reports in Inside JEB and Live Science 5 March 2021 and Journal of Experimental Biology 5 March 2021, doi:10.1242/jeb.237529.
Whilst studying the response of octopus skin to bright lights scientists at Ruppin Academic Center, Israel, researchers noticed that the animals moved their arms away from the light in a rapid reflex-like movement. They then studied this response more closely by keeping an octopus in a chamber in a dark covered tank and training it to reach out with one tentacle through a hole in the chamber to retrieve a piece of food. When they shone a light on the tentacle it retracted, even though the octopus could not see the light with its eyes. After a number of further studies they worked out the tips of the octopus arms were sensitive to light, and the reflex movement was controlled by the octopus’ brain receiving input from the tentacles and sending signals to the muscles in its arms.
The researchers suggest this light sensitive reflex is used by the octopus to ensure that all its arms are folded safely out of harm’s way when it folds itself into shaded a crevice or hole in order to rest.
To understand why this is a useful function, think of how you know where your arms and legs are and what position their joints are in. You do not have to look at them to know this because there are sensory receptors in your joints and muscles constantly sending signals to the brain. When you move masses of information are being sent to the brain, processed, and appropriate signals sent back to your muscles, without you having to think about it. This sense of body position is called proprioception, and involves a lot of nervous system processing to collate the information from joints and muscle and send appropriate signals to muscles to move. As the JEB article explains, “we only have four limbs to keep track of, so spare a thought for octopuses. With eight infinitely manoeuvrable limbs, how do these cephalopods keep track of them all?”
Nir Nesher commented: ‘Such a system would require a huge computational load’. The researchers concluded their study shows “how the octopus controls its arms using a cost-effective computational load and prevents its exposure to risk given its limited proprioceptive abilities.”
The JEB article is accompanied by a cartoon depicting an octopus telling a fish “Its lucky I’ve got a light sensitive reflex that stops my tentacles from creeping outside, otherwise they might get nibbled”.
Links: JEB, Live Science
Editorial Comment: The light sensitive reflex may keep the octopus tentacles away from predators who might want to take a bite out of them, but ‘luck’ did not set up this system. The combination of sensors and motor control needing only minimal computer power takes lots of intelligent planning and creative design, not luck or chance random evolution. Just ask any engineer trying to design a self-controlled robot that needs to be aware of where its limbs are at any instance, and respond to changes in the surrounding environment.
As the old negro spiritual goes its time to “Give God the Glory, Glory – Children of the Lord!”
Creation Research News 7 April 2021
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