Adrenoceptors in cryptic patterning of a flatfish, Pleuronectes americanus

Abstract

Cryptic patterns of winter flounder, Pleuronectes americanus, possess general background, dark band and white spot components that display differential chromatic responsiveness which has been studied pharmacologically in the current work. In vitro experiments with catecholamines and phentolamine demonstrate that a-adrenoceptors mediate melanosome aggregation in each pattern component. There was pattern-related differential responsiveness to noradrenaline, with ec50 values between 5.2 x 10-7 m for dark bands and 2.6 x 10"6 m for white spots. Phentolamine (1CT4 m) completely dispersed melanosomes, previously aggregated by noradrenaline (10_om), in 9 min for the white spots compared with approximately 82.5% dispersion in 15 min for the other two components. High degrees of melanosome aggregation induced in vitro by isoproterenol (3.15 x 10-5 m) were reversed differentially by propranolol (1CT4 m) indicating (3-adrenoceptor involvement, white spots displaying complete melanosome dispersion in 15 min with partial or no dispersion in the other two components. Phentolamine (1CT4 m) also reversed the effect of isoproterenol, so that the apparent (3-adrenoceptor synergism can be explained in terms of pattern-related presynaptic neuromodulation.

Flatfish (Pleuronectiformes) chromatic biology

“…In flatfish a-adrenoceptors mediate melanosome aggregation, based on relative potencies of catecholamines in accordance with Ahlquist's (1948) criteria, i.e., noradrenaline [ adrenaline [ isoproterenol, further supported by melanophore pharmacology (Fernando and Grove 1974a, b;Burton et al 1995). Such studies also indicate a 1 and a 2 subtypes, a 2 adrenoceptors being predominant in Pseudopleuronectes americanus (Burton and Vokey 2000b).…”

“…Physiological responses to substrate texture and colour Accounts of differential physiological changes in flatfish patterns have been grouped (Healey 1999) into those based on their major components observed in fish on black and white backgrounds (Burton 1975(Burton , 1981Burton et al 1995;Hewer 1926Hewer , 1931Kuntz 1915;Osborn 1939;Polimanti 1912), and those based on whole pattern changes in response to fine or coarse divisions of light and dark backgrounds, or to black and white or gradations of grey (Healey 1999;Mast 1914;Sumner 1911). Analyses of major components have provided a pragmatic model for experimentation, in vivo and in vitro, to facilitate a better understanding of physiological characteristics of overall chromatic behaviour.…”

“…High levels of b-adrenoceptor agonists can also have an inhibitory effect on the melanosome aggregation produced by noradrenaline or by electrical stimulation (Mayo and Burton 1998b). Melanophores of Pseudopleuronectes americanus display pattern-related ''transition ranges'' in noradrenaline concentrations between those inducing b-adrenoceptor mediated melanosome dispersion and those stimulating a-adrenoceptor mediated aggregation (Burton 2008), with distinct threshold values for individual pattern components (Burton et al 1995;Burton 2008). The relative extent of the noradrenaline ''transition range'' concentrations can be presented as dark bands [ general background [ white spots (Burton 2008).…”

“…The white spot melanophores of Pseudopleuronectes americanus display an a 1 -adrenoceptor bias, relative to the other components. Interestingly, melanophores from white spots display the highest noradrenaline concentration threshold for pigment aggregation in vitro (Burton et al 1995), yet their movements can also be the most rapid. Experimental manipulation of cAMP activity in vitro with forskolin, an adenyl-cyclase activator (Seamon and Daly 1981), results in reduced melanosome dispersion times (Burton 2005).…”

“…Such experiments with forskolin, together with those with a 1 -and a 2 -adrenoceptor agonists and antagonists (Burton and Vokey 2000b), both indicate that in Pseudopleuronectes americanus the white spot melanophores possess a different a 2 -/a 1 -adrenoceptor balance, with an a 1 bias. The possibility that white spot melanophores may also have an additional, non-background related, control mechanism has been suggested (Burton et al 1995), or these spots may constitute a separate basic pattern (Kelman et al 2006). However, differences in melanophore adrenoceptor subtypes, and associated intracellular secondary messenger, appear to be integral in flatfish white spot activity.…”

Flatfish (Pleuronectiformes) chromatic biology

“…In flatfish a-adrenoceptors mediate melanosome aggregation, based on relative potencies of catecholamines in accordance with Ahlquist's (1948) criteria, i.e., noradrenaline [ adrenaline [ isoproterenol, further supported by melanophore pharmacology (Fernando and Grove 1974a, b;Burton et al 1995). Such studies also indicate a 1 and a 2 subtypes, a 2 adrenoceptors being predominant in Pseudopleuronectes americanus (Burton and Vokey 2000b).…”

“…Physiological responses to substrate texture and colour Accounts of differential physiological changes in flatfish patterns have been grouped (Healey 1999) into those based on their major components observed in fish on black and white backgrounds (Burton 1975(Burton , 1981Burton et al 1995;Hewer 1926Hewer , 1931Kuntz 1915;Osborn 1939;Polimanti 1912), and those based on whole pattern changes in response to fine or coarse divisions of light and dark backgrounds, or to black and white or gradations of grey (Healey 1999;Mast 1914;Sumner 1911). Analyses of major components have provided a pragmatic model for experimentation, in vivo and in vitro, to facilitate a better understanding of physiological characteristics of overall chromatic behaviour.…”

“…High levels of b-adrenoceptor agonists can also have an inhibitory effect on the melanosome aggregation produced by noradrenaline or by electrical stimulation (Mayo and Burton 1998b). Melanophores of Pseudopleuronectes americanus display pattern-related ''transition ranges'' in noradrenaline concentrations between those inducing b-adrenoceptor mediated melanosome dispersion and those stimulating a-adrenoceptor mediated aggregation (Burton 2008), with distinct threshold values for individual pattern components (Burton et al 1995;Burton 2008). The relative extent of the noradrenaline ''transition range'' concentrations can be presented as dark bands [ general background [ white spots (Burton 2008).…”

“…The white spot melanophores of Pseudopleuronectes americanus display an a 1 -adrenoceptor bias, relative to the other components. Interestingly, melanophores from white spots display the highest noradrenaline concentration threshold for pigment aggregation in vitro (Burton et al 1995), yet their movements can also be the most rapid. Experimental manipulation of cAMP activity in vitro with forskolin, an adenyl-cyclase activator (Seamon and Daly 1981), results in reduced melanosome dispersion times (Burton 2005).…”

“…Such experiments with forskolin, together with those with a 1 -and a 2 -adrenoceptor agonists and antagonists (Burton and Vokey 2000b), both indicate that in Pseudopleuronectes americanus the white spot melanophores possess a different a 2 -/a 1 -adrenoceptor balance, with an a 1 bias. The possibility that white spot melanophores may also have an additional, non-background related, control mechanism has been suggested (Burton et al 1995), or these spots may constitute a separate basic pattern (Kelman et al 2006). However, differences in melanophore adrenoceptor subtypes, and associated intracellular secondary messenger, appear to be integral in flatfish white spot activity.…”

Flatfish (Pleuronectiformes) chromatic biology

“…In flatfish a-adrenoceptors mediate melanosome aggregation, based on relative potencies of catecholamines in accordance with Ahlquist's (1948) criteria, i.e., noradrenaline [ adrenaline [ isoproterenol, further supported by melanophore pharmacology (Fernando and Grove 1974a, b;Burton et al 1995). Such studies also indicate a 1 and a 2 subtypes, a 2 adrenoceptors being predominant in Pseudopleuronectes americanus (Burton and Vokey 2000b).…”

“…Physiological responses to substrate texture and colour Accounts of differential physiological changes in flatfish patterns have been grouped (Healey 1999) into those based on their major components observed in fish on black and white backgrounds (Burton 1975(Burton , 1981Burton et al 1995;Hewer 1926Hewer , 1931Kuntz 1915;Osborn 1939;Polimanti 1912), and those based on whole pattern changes in response to fine or coarse divisions of light and dark backgrounds, or to black and white or gradations of grey (Healey 1999;Mast 1914;Sumner 1911). Analyses of major components have provided a pragmatic model for experimentation, in vivo and in vitro, to facilitate a better understanding of physiological characteristics of overall chromatic behaviour.…”

“…High levels of b-adrenoceptor agonists can also have an inhibitory effect on the melanosome aggregation produced by noradrenaline or by electrical stimulation (Mayo and Burton 1998b). Melanophores of Pseudopleuronectes americanus display pattern-related ''transition ranges'' in noradrenaline concentrations between those inducing b-adrenoceptor mediated melanosome dispersion and those stimulating a-adrenoceptor mediated aggregation (Burton 2008), with distinct threshold values for individual pattern components (Burton et al 1995;Burton 2008). The relative extent of the noradrenaline ''transition range'' concentrations can be presented as dark bands [ general background [ white spots (Burton 2008).…”

“…The white spot melanophores of Pseudopleuronectes americanus display an a 1 -adrenoceptor bias, relative to the other components. Interestingly, melanophores from white spots display the highest noradrenaline concentration threshold for pigment aggregation in vitro (Burton et al 1995), yet their movements can also be the most rapid. Experimental manipulation of cAMP activity in vitro with forskolin, an adenyl-cyclase activator (Seamon and Daly 1981), results in reduced melanosome dispersion times (Burton 2005).…”

“…Such experiments with forskolin, together with those with a 1 -and a 2 -adrenoceptor agonists and antagonists (Burton and Vokey 2000b), both indicate that in Pseudopleuronectes americanus the white spot melanophores possess a different a 2 -/a 1 -adrenoceptor balance, with an a 1 bias. The possibility that white spot melanophores may also have an additional, non-background related, control mechanism has been suggested (Burton et al 1995), or these spots may constitute a separate basic pattern (Kelman et al 2006). However, differences in melanophore adrenoceptor subtypes, and associated intracellular secondary messenger, appear to be integral in flatfish white spot activity.…”

Flatfish (Pleuronectiformes) chromatic biology

“…In flatfish a-adrenoceptors mediate melanosome aggregation, based on relative potencies of catecholamines in accordance with Ahlquist's (1948) criteria, i.e., noradrenaline [ adrenaline [ isoproterenol, further supported by melanophore pharmacology (Fernando and Grove 1974a, b;Burton et al 1995). Such studies also indicate a 1 and a 2 subtypes, a 2 adrenoceptors being predominant in Pseudopleuronectes americanus (Burton and Vokey 2000b).…”

“…Physiological responses to substrate texture and colour Accounts of differential physiological changes in flatfish patterns have been grouped (Healey 1999) into those based on their major components observed in fish on black and white backgrounds (Burton 1975(Burton , 1981Burton et al 1995;Hewer 1926Hewer , 1931Kuntz 1915;Osborn 1939;Polimanti 1912), and those based on whole pattern changes in response to fine or coarse divisions of light and dark backgrounds, or to black and white or gradations of grey (Healey 1999;Mast 1914;Sumner 1911). Analyses of major components have provided a pragmatic model for experimentation, in vivo and in vitro, to facilitate a better understanding of physiological characteristics of overall chromatic behaviour.…”

“…High levels of b-adrenoceptor agonists can also have an inhibitory effect on the melanosome aggregation produced by noradrenaline or by electrical stimulation (Mayo and Burton 1998b). Melanophores of Pseudopleuronectes americanus display pattern-related ''transition ranges'' in noradrenaline concentrations between those inducing b-adrenoceptor mediated melanosome dispersion and those stimulating a-adrenoceptor mediated aggregation (Burton 2008), with distinct threshold values for individual pattern components (Burton et al 1995;Burton 2008). The relative extent of the noradrenaline ''transition range'' concentrations can be presented as dark bands [ general background [ white spots (Burton 2008).…”

“…The white spot melanophores of Pseudopleuronectes americanus display an a 1 -adrenoceptor bias, relative to the other components. Interestingly, melanophores from white spots display the highest noradrenaline concentration threshold for pigment aggregation in vitro (Burton et al 1995), yet their movements can also be the most rapid. Experimental manipulation of cAMP activity in vitro with forskolin, an adenyl-cyclase activator (Seamon and Daly 1981), results in reduced melanosome dispersion times (Burton 2005).…”

“…Such experiments with forskolin, together with those with a 1 -and a 2 -adrenoceptor agonists and antagonists (Burton and Vokey 2000b), both indicate that in Pseudopleuronectes americanus the white spot melanophores possess a different a 2 -/a 1 -adrenoceptor balance, with an a 1 bias. The possibility that white spot melanophores may also have an additional, non-background related, control mechanism has been suggested (Burton et al 1995), or these spots may constitute a separate basic pattern (Kelman et al 2006). However, differences in melanophore adrenoceptor subtypes, and associated intracellular secondary messenger, appear to be integral in flatfish white spot activity.…”