Studies on the light- and dark-adaptation of the colour of the crayfish, Astacus leptodactylus Eschscholz (Decapoda) controlled by the secretory activity of the central nervous system. II. Histomorphological picture of the neuroendocrine system related to the changes of illumination

Konok, István (1962) Studies on the light- and dark-adaptation of the colour of the crayfish, Astacus leptodactylus Eschscholz (Decapoda) controlled by the secretory activity of the central nervous system. II. Histomorphological picture of the neuroendocrine system related to the changes of illumination. A Magyar Tudományos Akadémia Tihanyi Biológiai Kutatóintézetének évkönyve, 29. pp. 27-37. ISSN 0365-3005

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Abstract

The histological assessment of various experiments on the light-adaptation of the Astacus leptodactylus on the basis of brain and eyestalk sections has led to the following conclusions: 1. The number of the granular cells in the blood and their saturation with granules varies in the hemolymph according to the phases of adaptation. 2. The granular cells should in fact be regarded as hyaline cells which, among other things, play an active part in the transportation of the chromactivating hormones in the hemolymph. 3. The circulation of granular cells below the basilar membrane, in the subretinal blood vessels is conspicous. Hence it seems probable that they have something to do with the hormonal regulation of the motion of the retinal pigments. 4. Granular cells and hyaline cells accumulate in the basal part of the eyestalks, immediately below the epithelium, and also on the periphery of the brain, outside and also below the neurilemma. 5. The stream of granular cells in the brain and in the capillaries of the individual medullae of the eyestalks, as well as within the individual groups of secretory cells between the cells can clearly be observed. 6. The changes in the histomorphological picture of the sinus gland closely follow the course of the release of hormones corresponding to darkadaptation. 7. In the A- and В-type cells of the brain and the eysetalk the chromatophorotropic factors of a dark-adapting character and capable of being isolated, could not be localized. The secretion of certain hormones presumably goes on incessantly, the rate of secretion may, however, accelerate or decelerate according to the prevailing conditions. 8. The secretory cells of the eyestalk are not condensed on the medulla terminális but, both groups of A- and В-type cells can be observed on the medulla interna as well as is on the medulla externa, in a lateral or intermedullar position, what is more, even between the sinus gland axon fibre terminations. 9. Also within the morphologically uniform major groups of secretory cells clearly isolated minor cell groups can be seen near each other. These groups are in a synchronous functional phase. It may be presumed that even in the morphologically identical В-type cells various hormones may be produced. 10. The results of the experiments with ligated eyestalks indicate that hormones are released into the hemolymph directly from the brain, too. 11. On the chiasma externa a formation situated in one layer below the lamina ganglionaris and reminiscent of the terminations of axon fibres can be observed. It shows an activity similar to, and synchronous with, that of the sinus gland. 12. The fibres running from the retinal cells to the lamina ganglionaris assume a violet colour after the withdrawal of the proximal retinal pigment above the basilar membrane. The axon tissue arranged perpendicularly to the axis of the eyestalk below the lamina ganglionaris stains in a similar way. 13. The movement of the proximal retinal pigments of the ocelli and the pigment migration in the chromatophores indicate that light-adaptation is a slower process than dark-adaptation. 14. The hypothesis that light-adaptation (unlike the mechanism of darkadaptation) is due to the constant hormonal concentration, at a given level, of the hemolymph, seems to be supported in different respects. The hormonal concentration becomes active when the secretion by factors inducing darkadaptation of an antagonistic character is suspended.

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