Natures wonders: the light dance of squid (Introduction)

by David Turell , Sunday, April 04, 2021, 15:44 (1327 days ago) @ David Turell

Amazing controls of of light reflection in their skin from brain connections:

http://oceans.nautil.us/feature/686/the-light-magic-of-squid?mc_cid=1196952500&mc_e...

{These schools of squids coordinate their movements through their lateral line receptors and their vision, enabling collective movement almost instantaneously.

"Squid intelligence is movement, in this sense of moving through the water, and in other ways as well. The flashing colors and shimmering of their skin heighten the dynamics of their continually changing and moving arms and mantle. Anyone who has seen living cephalopods has felt compelled to remark that their brilliant colors make them among the most beautiful of all animals,

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"The actual colour changes are caused by the chromatophores, complex organs numbering in the hundreds of thousands which can be described as sacs that are opened and closed by the surrounding muscles. Muscular contraction opens individual sacs to reveal the granular pigment within, and relaxation closes the sacs to make the colour disappear. The muscles and chromatophores are controlled by the same lobes of the brain that control the funnel, making for a direct connection between jet propulsion and colouration. The nervous control of the muscles also means that expansion and contraction can take place very rapidly, with some chromatophores expanded and others closed to create patterns in the skin that are impossible in other animals. Tracing the neurological line of control, scientists have learned that chromatophores are regulated by the eyes, which send information to the regulating lobe in the brain that ensures all parts of the squid’s body respond together, just as in the case of the muscular contractions in jet propulsion. The neural control can also determine the brightness, contrast and colour of the patterns, which means that they can appear, disappear or change almost instantly, enabling a squid to shift its physical appearance continually to confront predators and prey with completely different shapes. Not only are perception and motion intertwined, but they are also connected directly with body patterning.

"Their luminescence can be understood as light altered—digested, if you will—into intentional actions.

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"The brief acute patterns squids make are innumerable. Among them, ‘very dark’ occurs either as a single brief flash or as several flashes over the span of five seconds. The brief version appears to work as a warning of some threat coming from another squid or some other species (‘a person in the laboratory’), and the longer version appears aimed at startling the other creature. Another pattern, called the ‘blanch-ink-jet maneuver’, is believed to be universal among squids. The individual blanches clear, jets away, and ejects an inky ‘pseudomorph’, or decoy, that remains in the approximate position from which the squid swam off. This defensive action confuses an attacker that believes the ink cloud to be the squid, which has safely left the area.

"The chromatophores lie over reflective cells called iridophores, which change the wavelength of light bouncing off them. As chromatophores expand and contract, they cover and uncover the underlying reflective cells without extinguishing the reflected light, giving an effect of changing colors and iridescence all at once. The colors might create patterns, while the iridescence shifts the light from non-polarized to polarized, and towards the shorter wave length of blue light. The iridophores vary in thick- ness, which also affects the wavelengths that they each reflect. Structurally, they contain stacks of protein plates interspersed by cytoplasm, and the thicker the protein stack, the more reflected light moves towards the longer wavelengths of yellow and red, while the thinner stacks reflect short wavelengths of blue light. This reflecting mechanism has been compared to the iridescent surface of soap bubbles, in that the tone and quality of the light shifts so continually that identification of a particular colour is impossible.

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"The control of the photophores comes from photosensitive receptors lying close to the olfactory lobe in the brain. Two groups of receptors appear to operate: one dorsally, which scientists believe registers downwelling light, and the other ventrally, which would register the light emitted by the ventral photophores. Generally, the photophores emit a weak blue light, matching the intensity of the light filtered through the water. On the basis of this detail, scientists surmise that the photophores on the underside function to blend individuals into the down-streaming light, so that predators from below cannot see them."

Comment: Amazing complex organs force reflecting light to make color patterns. The schooling is the same movement pattern as in masses of the Wildebeest migration pattern across the Serengeti Plaines and streams with predators working only on the edges of the mass. Great evidence of design. I can't imagine stepwise development of the reflectors by chance.