Sensitivity of winter flounder melanophores after removal of the epidermis from in vitro preparations

Abstract

Winter flounder Pleuronectes americanus has a thick epidermis which was removed from scale slips by incubation in a medium including 1% ethylenediaminetetraacetic acid (EDTA) for up to 2 h. Neurally mediated responses of dermal melanophores to K + and Na + , and to exogenous noradrenaline (10 5 ) were 1·5 to three times faster without the epidermis-mucus barrier; -melanophore stimulating hormone (MSH) evoked extensive pigment dispersion only without the epidermis. Thus, cellular viability after epidermal removal is not restricted to melanophores, nerve terminals can provide an additional indicator. The sensitivity to -MSH in vitro, is an important observation since in vivo reports have not indicated that this hormone has a role in the physiological responsiveness of these melanophores in flatfish. 1998 The Fisheries Society of the British Isles

The relative in vitro responsiveness of melanophores of winter flounder to α-MSH and MCH

“… melanophores with AF alone, the subsequent pattern-related differences in dispersion with increasing concentrations of -MSH reflect variation in density and/or affinity of adrenoceptors as well as of MSH receptors. The general background melanophores were the most sensitive to -MSH and those from the white spots least in the presence of catecholamine, released by AF, indicating a higher -adrenoceptor density (Vokey & Burton, 1998) relative to MSH receptors in the white spots. Adrenaline from chromaffin tissue may be important in the stress-related paling of white spots which can be observed (Osborn, 1939) in otherwise dark flounder.…”

“…Experiments involving hypophysectomy, spinal section and MSH injections (Burton, 1981(Burton, , 1993 provided little evidence for MSH involvement in the control of flounder melanophore responsiveness, although in vitro experiments (Vokey & Burton, 1998) do provide evidence for the occurrence of -MSH receptors on these effectors in this species, although the experiments involved only the general background melanophores.…”

The relative in vitro responsiveness of melanophores of winter flounder to α-MSH and MCH

“… melanophores with AF alone, the subsequent pattern-related differences in dispersion with increasing concentrations of -MSH reflect variation in density and/or affinity of adrenoceptors as well as of MSH receptors. The general background melanophores were the most sensitive to -MSH and those from the white spots least in the presence of catecholamine, released by AF, indicating a higher -adrenoceptor density (Vokey & Burton, 1998) relative to MSH receptors in the white spots. Adrenaline from chromaffin tissue may be important in the stress-related paling of white spots which can be observed (Osborn, 1939) in otherwise dark flounder.…”

“…Experiments involving hypophysectomy, spinal section and MSH injections (Burton, 1981(Burton, , 1993 provided little evidence for MSH involvement in the control of flounder melanophore responsiveness, although in vitro experiments (Vokey & Burton, 1998) do provide evidence for the occurrence of -MSH receptors on these effectors in this species, although the experiments involved only the general background melanophores.…”

The physiology of flatfish chromatophores

“…Concentration-response data for noradrenaline Ͼ10 -8 M indicate that white spot melanophores are the least sensitive, with a high concentration threshold, compared with the other two pattern components that show no difference (Vokey and Burton, 1998). Noradrenaline response rates are the fastest for the white spot melanophores and slowest for those from dark bands (Vokey and Burton, 1998).…”

“…Although white spot melanophores demonstrate the most rapid aggregation rate in response to K ϩ ions and noradrenaline, they also have the highest concentration thresholds with noradrenaline and ␣-adrenoceptor agonists. The melanophores of the white spots and dark bands, which display excitement responses counter to background-related responses, may have additional regulatory factors and receptors (Vokey and Burton, 1998). Such regulatory factors could include a separate innervation (Hewer, 1926) for the white spots, in addition to that from the central processing and pigmento-motor neural pathway for background-related paling.…”

Pigmentation development in hatchery-reared flatfishes

“…This capacity is based on neurotransmitter-mediated changes in the melanophores. These cytological adjustments, which affect the concentration of pigment granules in different areas of the skin (Baker, 1991;Fujii, 1993;Vokey & Burton, 1998), are dynamic and reversible. In contrast, ontogenetic changes in flatfish pigmentation are based primarily on the differentiation or disappearance of chromatoblasts and are generally not reversible (though exceptions have been reported: Benetti, 1997;Denson & Smith, 1997).…”

The relative in vitro responsiveness of melanophores of winter flounder to α-MSH and MCH

“… melanophores with AF alone, the subsequent pattern-related differences in dispersion with increasing concentrations of -MSH reflect variation in density and/or affinity of adrenoceptors as well as of MSH receptors. The general background melanophores were the most sensitive to -MSH and those from the white spots least in the presence of catecholamine, released by AF, indicating a higher -adrenoceptor density (Vokey & Burton, 1998) relative to MSH receptors in the white spots. Adrenaline from chromaffin tissue may be important in the stress-related paling of white spots which can be observed (Osborn, 1939) in otherwise dark flounder.…”

“…Experiments involving hypophysectomy, spinal section and MSH injections (Burton, 1981(Burton, , 1993 provided little evidence for MSH involvement in the control of flounder melanophore responsiveness, although in vitro experiments (Vokey & Burton, 1998) do provide evidence for the occurrence of -MSH receptors on these effectors in this species, although the experiments involved only the general background melanophores.…”

The physiology of flatfish chromatophores

“…Concentration-response data for noradrenaline Ͼ10 -8 M indicate that white spot melanophores are the least sensitive, with a high concentration threshold, compared with the other two pattern components that show no difference (Vokey and Burton, 1998). Noradrenaline response rates are the fastest for the white spot melanophores and slowest for those from dark bands (Vokey and Burton, 1998).…”

“…Although white spot melanophores demonstrate the most rapid aggregation rate in response to K ϩ ions and noradrenaline, they also have the highest concentration thresholds with noradrenaline and ␣-adrenoceptor agonists. The melanophores of the white spots and dark bands, which display excitement responses counter to background-related responses, may have additional regulatory factors and receptors (Vokey and Burton, 1998). Such regulatory factors could include a separate innervation (Hewer, 1926) for the white spots, in addition to that from the central processing and pigmento-motor neural pathway for background-related paling.…”

Pigmentation development in hatchery-reared flatfishes

“…This capacity is based on neurotransmitter-mediated changes in the melanophores. These cytological adjustments, which affect the concentration of pigment granules in different areas of the skin (Baker, 1991;Fujii, 1993;Vokey & Burton, 1998), are dynamic and reversible. In contrast, ontogenetic changes in flatfish pigmentation are based primarily on the differentiation or disappearance of chromatoblasts and are generally not reversible (though exceptions have been reported: Benetti, 1997;Denson & Smith, 1997).…”

The relative in vitro responsiveness of melanophores of winter flounder to α-MSH and MCH

“… melanophores with AF alone, the subsequent pattern-related differences in dispersion with increasing concentrations of -MSH reflect variation in density and/or affinity of adrenoceptors as well as of MSH receptors. The general background melanophores were the most sensitive to -MSH and those from the white spots least in the presence of catecholamine, released by AF, indicating a higher -adrenoceptor density (Vokey & Burton, 1998) relative to MSH receptors in the white spots. Adrenaline from chromaffin tissue may be important in the stress-related paling of white spots which can be observed (Osborn, 1939) in otherwise dark flounder.…”

“…Experiments involving hypophysectomy, spinal section and MSH injections (Burton, 1981(Burton, , 1993 provided little evidence for MSH involvement in the control of flounder melanophore responsiveness, although in vitro experiments (Vokey & Burton, 1998) do provide evidence for the occurrence of -MSH receptors on these effectors in this species, although the experiments involved only the general background melanophores.…”

The physiology of flatfish chromatophores

“…Concentration-response data for noradrenaline Ͼ10 -8 M indicate that white spot melanophores are the least sensitive, with a high concentration threshold, compared with the other two pattern components that show no difference (Vokey and Burton, 1998). Noradrenaline response rates are the fastest for the white spot melanophores and slowest for those from dark bands (Vokey and Burton, 1998).…”

“…Although white spot melanophores demonstrate the most rapid aggregation rate in response to K ϩ ions and noradrenaline, they also have the highest concentration thresholds with noradrenaline and ␣-adrenoceptor agonists. The melanophores of the white spots and dark bands, which display excitement responses counter to background-related responses, may have additional regulatory factors and receptors (Vokey and Burton, 1998). Such regulatory factors could include a separate innervation (Hewer, 1926) for the white spots, in addition to that from the central processing and pigmento-motor neural pathway for background-related paling.…”

Pigmentation development in hatchery-reared flatfishes

“…This capacity is based on neurotransmitter-mediated changes in the melanophores. These cytological adjustments, which affect the concentration of pigment granules in different areas of the skin (Baker, 1991;Fujii, 1993;Vokey & Burton, 1998), are dynamic and reversible. In contrast, ontogenetic changes in flatfish pigmentation are based primarily on the differentiation or disappearance of chromatoblasts and are generally not reversible (though exceptions have been reported: Benetti, 1997;Denson & Smith, 1997).…”