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Mäthger et al., 2003 ). Neurotransmitter receptors are mediators of changes in the
distance between platelets. The shifts in the light wavelengths reflected by gua-
nine platelets is determined by corresponding changes (increases and decreases) in
the length of microtubules and, consequently, of the distance between reflecting plate-
lets ( Kasukawa et al., 1987 ). Thus, the change in the length of interplate microtu-
bules changes the wavelength and the color of light reflected by the skin. This is the
“Venetian blind model” of adaptive color change ( Yoshioka et al., 2011 ). The instan-
taneous change of body color is not instinctive in the classical meaning of the word,
i.e., it does not result from any “fixed action pattern.” Far from a standard indivis-
ible response, it implies a practically infinite number of responses (i.e., the ability to
change its body color in a multitude of ways so that it matches the perceived back-
ground or body color and patterns of other animals).
How does the animal translate the perceived color and pattern into its own body
color and pattern? How does it verify whether the induced change matches the per-
ception? While the neurobiological mechanism of processing of these stimuli and
their “translation” in the brain is still unknown, we do know the neural pathway that
leads to this form of astonishing adaptive pigmentless coloration.
The visual input from the retina is transmitted, via the optic nerve, to the CNS,
where its processing results in an adaptive neural response that determines the adap-
tive coloration and pattern of the fish. The CNS selects the adaptive response, with
the sympathetic nervous system acting as the mediator of the adaptive changes of
skin color ( Goda and Fujii, 1998 ). Severance of the sympathetic nerves prevents the
fish from displaying the adaptive change of color and pattern, leading to the dark-
ening of skin, typical of depression of the sympathetic activity, and the activation
instead of the parasympathetic system in chromatophores ( Fujii, 2000 ).
If the nervous system adaptively regulates the length of microtubules in the skin
cells of fish to accomplish finely tuned adaptive coloration, is there any reason why
it could not adaptively regulate the length of egg microtubules, and, consequently,
the spatial arrangement of maternal factors in the egg?
References
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Amberg, D.C., 1998. Three-dimensional imaging of the yeast actin cytoskeleton through the
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Aristotle, 1910. The History of Animals. Book V. Part 1 (D'Arcy Wentworth Thompson, Trans.).
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prolactin release changes during pregnancy in pony mares. J. Endocrinol. 169, 511-518.
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