An Edentate From The Oligocene Of Wyoming

Author : Priscilla Rasquin
Publisher :
ISBN 13 :
Total Pages : 468 pages
Book Rating : 4.3/5 ( download)

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Download or read book Studies in the Control of Pigment Cells and Light Reactions in Recent Teleost Fishes written by Priscilla Rasquin and published by . This book was released on 1959 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pt. 1. "The histomorphology of the pineal area is described for 33 species of teleosts. The pineal organ is composed of an end-vesicle, a stalk, and a short pedicle, but variations in size and development of the vesicle and stalk create great differences in the morphology of the organ in different species. 2. In general, those species in which the pineal organ is exposed to light passing through transparent overlying tissues, or in which the pineal area can be exposed to light by concentration of pigment granules in over-lying chromatophores, show a specialization of the pineal organ. The end-vesicle in particular covers a wide area, spreading over parts of the forebrain and optic lobes, with the surface area of pineal cells greatly increased by invaginations and convolutions of the walls. Those species in which the pineal organ is deeply buried under many tissue layers are found to have a more simplified structure, with the vesicle limited to a simple sac. 3. Cytological study shows that the pineal is a complex organ probably having both sensory and secretary functions. Nerve endings seen near the pineal cells are connected with ganglion cells. Fibers from the ganglion cells progress down the walls of the stalk and enter the habenular commissure. Two types of epithelioid cells form the inner walls of the pineal vesicle and stalk, resting on a connective-tissue, basement membrane. These epithelioid or pineal cells either are sloughed off into the lumen, or parts of them are broken off into the lumen to form an apocrine secretion. 4. The apocrine secretion of the pineal can be delivered to the cerebrospinal fluid through the opening in the base of the stalk or pedicle that connects the lumen of the pineal stalk with the third ventricle of the diencephalon. 5. The pineal secretion in teleosts is composed, at least in part, of glycogen and glyco-protein. In some species, as Atherina stipes, the pineal cells accumulate glycogen during hours of darkness. The quantity of glycogen decreases during hours of light. 6. Intraperitoneal implantation of fresh Atherina pineals caused no observable effect on pigmentation in Cyprinodon. 7. Pinealectomy in Astyanax had no effect on pituitary, thyroid, or gonads and no observable effect on pigmentation. No significant changes in phototaxis were observed, owing perhaps to the dense pigmentation over the top of the head in this species. 8. Although no specific sensory cells were discovered in the teleost pineals, the behavior of fishes shows a sensory influence of this area of the brain. Other results of this report indicate that there is no evidence for an endocrine function of the secretion of the teleost pineal gland" -- pt. 2. "Thirty-five species of teleosts were injected with adrenalin or with intermedin or with both hormones at different times. 2. Fishes can be grouped in three categories according to the reaction of the melanophore system to adrenaline: (1) fishes in which adrenalin causes concentration of pigment granules within all the melanophores, (2) fishes in which only the internal melanophores show pigment concentration, and (3) fishes in which none of the melanophores is affected by adrenalin injection. 3. In some species, dermal melanophores are not concentrated by the effects of adrenalin injection but are responsive to the direct application of the hormone to the skin. 4. The lipophores respond to adrenalin either by dispersion or concentration of pigment granules, depending upon the species. 5. Leucophores respond to adrenalin injection by dispersion of guanin granules. 6. Dispersion of melanin granules in chromatophores as a response to intermedin was confined to Ameiurus, Gambusia, Astyanax, and Atherina among the species used for this report. All other species showed no reaction of melanophores to intermedin. 7. All species responded to intermedin by dispersion of lipophores. 8. Six mammalian anterior pituitary preparations were tested for their effects on the pigmentation of the fresh-water characin Astyanax mexicanus and the marine goby Bathygobius soporator. These hormones were FSH, LH, TSH, MSH, prolactin, and growth hormone. In addition, ACTH was used on Bathygobius. 9. MSH administration caused dispersion of melanin granules in the melanophores of Astyanax. No pigmentary reactions were noted in this species after injection of any other pituitary fractions. 10. Administration of all the anterior lobe preparations caused dispersion of pigment granules in the xanthophores of Bathygobius. No reaction was noted in the melanophores. 11. MSH was administered to eight other species with the following results: in fresh water, Ameiurus nebulosus, dispersion of melanophores; in sea water, Gambusia sp. and Atherina stipes, dispersion of melanophores; Cyprinodon baconi and Monacanthus ciliatus, no reaction; Gambusia sp., Lutianus apodus, Irideo bivitatta, and Chaetodon striatus, dispersion of xanthophores or erythrophores"--P. 64-65.