Migration Of Pigment Granules Research Articles

Photomechanical changes in the ommatidia of theLimulus lateral eye during light and dark adaptation

1. The photomechanical changes which occur inLimulus lateral eye during long-term (8 hours or longer) dark-light adaptation were studied via light microscopy. 2. The results indicated that, in addition to the migration of protective pigment granules previously observed, morphological changes occur in cone cells, retinular cell rhabdomeral membranes and eccentric cell dendrites during adaptation (Figs. 1, 2 and 3). These changes were confined to the illuminated (or light-deprived) portion of the eye and did not depend on intact neural connections with the brain. 3. Eyes excised during daylight hours from animals maintained in darkness appeared partially “light-adapted” suggesting circadian effects (Fig. 4). 4. Large vacuole-Iike structures formed in retinular cells during prolonged (24–48 hour) exposure to fluorescent room light and disappeared during a subsequent dark period (Fig. 5). 5. It is possible that the changes which occur in the rhabdomeral membranes of retinular cells and the eccentric cell dendrite during light-dark adaptation affect the electrotonic coupling which exists between these cells.

The comparative effects of teleost and beef pituitary on chromatophores of cold-blooded vertebrates.

1. Fish and beef acetone-desiccated pituitaries cause a distal migration of pigment granules in melanophores when injected into the elasmobranch Urobatis halleri, the teleost Ameiurus melas, the amphibians Hyla regilla and Rana pipiens, and the reptile Anolis carolinensis. These preparations not only disperse melanin but also induce a proximal migration of the white granules in leucophores of Rana pipiens larvae.2. Fish pituitary injected into the teleosts Gambusia affinis, Fundulus parvipinnis, Girella nigricans, Gillichthys mirabilis, Lepomis cyanellus and Leuresthes tenuis causes a proximal migration of melanin and, at least in the first three species, a distal migration of pigment in the xanthophores. Desiccated fish brain, beef whole gland, beef posterior lobe and commercial pituitrin have no obvious effect on their chromatophores.3. There is an opposite migration of melanin in certain different species of teleosts treated with fish pituitary. The diverse chromatic reaction of teleosts may have phylogenetic significance. The more primitive teleosts appear to react like other classes of cold-blooded vertebrates, whereas the higher teleosts, which have diverged more from the common line of vertebrate evolution, do not.4. There is a differential in reaction of different types of chromatophores in a single species to treatment with the same pituitary preparations.5. Pituitary material from different sources may have unlike chromatophorotropic action. Beef and fish pituitary have a similar action (expansion) on melanophores of Urobatis, Ameiurus, Rana and Anolis. However, on such teleosts as Fundulus and Girella, fish extracts have the opposite effect and mammalian extracts have no apparent effect.