Mammalians process their photoreceptions through lateral eyes; however, non-mammalian vertebrates and invertebrates possess additional extraretinal photoreceptors over their bodies to detect light stimuli. Chromatophores, i.e. dermal specialized pigment cells, play important roles in the regulation of body patterns. Since chromatophores derive from neural crest, they share the common embryonic origin with retina. Recent evidence shows that they are light-sensitive due to opsin expression. In the present study, the expression of seven cone opsins was detected in tilapia caudal fin tissues. Moreover, distinct photoresponses were found in two chromatophore types. Regardless of stimulating wavelengths, melanophores tend to disperse and maintain cell shape at dispersion stage by shuttling pigment granules. Conversely, erythrophores respond to light in a wavelength-dependent manner. The opsin expression profiles of melanophores and erythrophores imply SWS1 and RH2 group genes may play important roles in chromatophore photoresponses. Through measuring photosensitivity, I suggest the two opsins play opposite roles in light-induced translocations of pigment granules within erythrophores: SWS1 for aggregations at UV and short wavelength regions and RH2b for dispersion in middle/long wavelengths. An antagonistic interaction occurs in the overlapping of the absorbance spectra of the two opsins. I also found that the photoresponses take place along with the occurrence of the change of cell membrane potential. In addition, the effect of different light backgrounds (broad spectrum, short wavelength-rich, and red-shifted light conditions) on the photosensitivity of tilapia erythrophores was investigated. I found that the major opsin classes (SWS1 and RH2b) responsible for photoresponses remain constant in three groups of erythrophores. Together, I postulate that melanophores may serve as a light filter in integumentary tissues, and the chromatically antagonistic mechanism enables tilapia erythrophores to sense the subtle change of environmental photic condition and to fine-tune pigmentation. I also investigated the ontogenetic change of photoresponses of rainbow trout melanophores. Distinct photoresponses were found in parrs and smolts. Furthermore, smolt melanophores responded to light in a wavelength-dependent manner. Since the change of coloration and visual system during smoltification of salmonids is regulated by thyroid hormone (TH), I suggest that the development of melanophore photosensitivity is associated to TH as well. / Thesis (Ph.D, Biology) -- Queen's University, 2013-08-27 09:57:22.907

Mammalians process their photoreceptions through lateral eyes; however, non-mammalian vertebrates and invertebrates possess additional extraretinal photoreceptors over their bodies to detect light stimuli. Chromatophores, i.e. dermal specialized pigment cells, play important roles in the regulation of body patterns. Since chromatophores derive from neural crest, they share the common embryonic origin with retina. Recent evidence shows that they are light-sensitive due to opsin expression. In the present study, the expression of seven cone opsins was detected in tilapia caudal fin tissues. Moreover, distinct photoresponses were found in two chromatophore types. Regardless of stimulating wavelengths, melanophores tend to disperse and maintain cell shape at dispersion stage by shuttling pigment granules. Conversely, erythrophores respond to light in a wavelength-dependent manner. The opsin expression profiles of melanophores and erythrophores imply SWS1 and RH2 group genes may play important roles in chromatophore photoresponses. Through measuring photosensitivity, I suggest the two opsins play opposite roles in light-induced translocations of pigment granules within erythrophores: SWS1 for aggregations at UV and short wavelength regions and RH2b for dispersion in middle/long wavelengths. An antagonistic interaction occurs in the overlapping of the absorbance spectra of the two opsins. I also found that the photoresponses take place along with the occurrence of the change of cell membrane potential. In addition, the effect of different light backgrounds (broad spectrum, short wavelength-rich, and red-shifted light conditions) on the photosensitivity of tilapia erythrophores was investigated. I found that the major opsin classes (SWS1 and RH2b) responsible for photoresponses remain constant in three groups of erythrophores. Together, I postulate that melanophores may serve as a light filter in integumentary tissues, and the chromatically antagonistic mechanism enables tilapia erythrophores to sense the subtle change of environmental photic condition and to fine-tune pigmentation. I also investigated the ontogenetic change of photoresponses of rainbow trout melanophores. Distinct photoresponses were found in parrs and smolts. Furthermore, smolt melanophores responded to light in a wavelength-dependent manner. Since the change of coloration and visual system during smoltification of salmonids is regulated by thyroid hormone (TH), I suggest that the development of melanophore photosensitivity is associated to TH as well. / Thesis (Ph.D, Biology) -- Queen's University, 2013-08-27 09:57:22.907

Detection of both biological and chemical environmental toxicants is essential in the assessment of risk to human health. Cell-based biosensors are capable of activity- based detection of toxicity. Chromatophore cells, responsible for the pigmentation of poikilothermic animal, have shown immense potential as cell-based biosensors in the detection of a broad range of environmental toxicants. Chromatophore cells possess the motile pigment granules that intracellularly aggregate or disperse in response to external stimuli. Previous studies have assessed chromatophore cells isolated from red Betta splendens and grey Oncorhynchus tschawytscha fish for use as a biosensor. The objective of this study was to describe blue B. splendens chromatophore cells in tissue culture. Blue B. splendens chromatophore cells were assessed for their longevity in tissue culture and their responses to previously established control agents. Blue B. splendens chromatophore cells were exposed to select chemicals and pathogenic bacteria to assess their ability to respond to environmental toxicants. Three concentrations of mercuric chloride, methyl mercuric chloride, paraquat, sodium arsenite, sodium cyanide chemicals were tested. Bacillus cereus, Bacillus subtilis, Salmonella enterica serovar Enteritidis, and Salmonella enterica serovar Typhimurium were tested. Red B. splendens chromatophore cells were subjected to the select chemical and bacterial toxicants, and observed for their responses. The data collected in this and previous studies were compiled to compare chromatophore cell responses to a broad range of environmental toxicants. Chromatophore cells isolated from both blue and red B. splendens were responsive to methyl mercuric chloride and sodium arsenite. Grey O. tschawytscha chromatophore cells have shown responsiveness to mercuric chloride and sodium arsenite. Blue and red B. splendens chromatophore cells were both responsive to B. cereus and both Salmonella serovars. Grey O. tschawytscha have previously been shown to respond to B. cereus as well. In conclusion, this study reports the chromatophore cells isolated from blue B. splendens in tissue culture and showed similar responsiveness to the selected chemical and bacterial environmental toxicants as chromatophore cells isolated from red and grey colored fish. This study provides compelling evidence that the chromatophore response is not dependent on fish color and that chromatophore cells used for a cell-based detection system may be isolated from different colored fish. / Graduation date: 2012

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19530号 / 理博第4190号 / 新制||理||1601(附属図書館) / 32566 / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 朝倉 彰講師宮崎 勝己, 教授 曽田 貞滋 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM