Apoptosis in skin pigment cells of the medaka, Oryzias latipes (Teleostei), during long-term chromatic adaptation: the role of sympathetic innervation

Abstract

Many teleost fish can adapt their body color to a background color by changing the morphology and density of their skin pigment cells. Melanophore density in fish skin decreases during long-term adaptation to a white background. Although cell death, especially apoptosis, is thought to be involved in these morphological changes, there are no data clearly supporting this mechanism. Using medaka fish, Oryzias latipes, we observed that, on a white background, melanophore size was reduced first and this was followed by a decrease in melanophore density caused by gradual cell death. The process of cell death included loss of cell activity, cell fragmentation, phagocytosis of the fragments, and clearance via the epidermis. Apoptosis was assessed by the appearance of phosphatidylserine on the cell surface of melanophores that had lost motile activity, and DNA fragments involved in cell fragmentation were detected by the TUNEL (TDT-mediated dUTP-biotin nick end-labeling) assay. However, when chemically denervated fish were used, although melanophore size was reduced as expected, cell death was suppressed even on a white background. In skin tissue culture, apoptosis in melanophores was stimulated significantly by norepinephrine, but not by melanin-concentrating hormone. These results indicate that melanophore density decreases by apoptosis, and suggest that sympathetic innervation has an important role in the regulation of apoptosis in melanophores. In analogous fashion, leucophores showed a significant decrease in density with an increase of cell death on a black background. We suggest that apoptosis regulates the balance of pigment cells in the skin of medaka fish to adapt their body color to a particular background.

Larvicultura de piabanha-do-pardo em aquários de cores diferentes

“…Algumas espécies de peixes, como os teleósteos, ajustam sua pele em resposta a mudanças na cor de fundo (Sugimoto et al, 2000), o pode ocorrer como resultado final de mecanismos de defesa (Bond, 1996). Este processo de mudança de cor, denominado de adaptação de fundo, é usado para estudar comunicações neuroendócrinas (Rotllant et al, 2003).…”

“…Este processo de mudança de cor, denominado de adaptação de fundo, é usado para estudar comunicações neuroendócrinas (Rotllant et al, 2003). Segundo Sugimoto (2000) e Van der Salm et al (2006), estas mudanças de cor são decorrentes da agregação e da dispersão de pigmento, e das alterações na quantidade de pigmento e no número de cromatóforos.…”

“…A cor do ambiente está relacionada à reprodução (Volpato et al, 2004), à visão e a aspectos adaptativos, como mudanças na pigmentação da pele dos peixes (Sugimoto et al, 2000). Muitos animais marinhos adéquam a cor da sua pele à do ambiente em que vivem, como a espécie Pagrus pagrus (pargo-vermelho) (Rotllant et al, 2003;Van Der Salm et al, 2004).…”

Possible Involvement of Cone Opsins in Distinct Photoresponses of Intrinsically Photosensitive Dermal Chromatophores in Tilapia Oreochromis niloticus

“…For example, when medaka Oryzias latipes are adapted to white background, their body colors become paler due to the aggregation, reduced cell size, or even melanophore apoptosis [19], [50]. These results highlight the importance of environmental photic factors on body color patterns; however, how animals coordinate visual cues with their body color performances remains unclear.…”

“…They are capable of responding morphologically (in number or size) or physiologically (through translocation of inner pigment granules, i.e. aggregation or dispersion) in order to execute long-term or immediate color pattern changes, respectively [18], [19]. Integumentary color change is achieved in three ways: 1) through pigment granule motility, 2) through reflective plates within chromatophores, and 3) through coordination of different chromatophore classes and/or other tissues [20], [21].…”