Differential light intensity and spectral sensitivities of Atlantic salmon, European sea bass and Atlantic cod pineal glands ex vivo

Jun 9, 2009General and comparative endocrinology

Different light brightness and color sensitivities of the pineal glands in Atlantic salmon, European sea bass, and Atlantic cod tested outside the body

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Abstract

Atlantic cod exhibits 100 to 1000 times greater sensitivity to light intensity compared to European sea bass and Atlantic salmon.

Different species of temperate teleosts show unique responses to light intensity and spectral composition in melatonin suppression.
Cod's sensitivity to light intensity is significantly higher than that of sea bass and salmon.
Red light is less effective at suppressing melatonin in salmon compared to blue and green light.
The study provides the first evidence of relative photoreception in cod, indicating that day intensity influences night-time melatonin suppression.
A substantial change in day intensity can significantly alter the intensity response curve for melatonin suppression.

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Photoperiod is perceived by pineal photoreceptors and transduced into rhythmic melatonin signals. These rhythms can be influenced by light intensity and spectral content. In this study we compared the light sensitivity of Atlantic salmon, European sea bass and Atlantic cod by testing ex vivo the effect of different intensities and narrow bandwidth lights on nocturnal melatonin suppression by isolated pineal glands in a flow-through culture system. Using combinations of neutral density and bandpass interference filters we tested a range of light intensities (ranging from 1.22x10(13) to 3.85x10(6) photons s(-1) cm(-2)) and three wavelengths of 80 nm width (472, 555 and 661 nm corresponding to blue, green and red, respectively). Results showed clear species specific light intensity and spectral sensitivities, with cod being from 100 to 1000 times more sensitive than sea bass and salmon. Regarding the influence of spectrum, red light was less efficient on suppressing melatonin than blue and green in salmon but results were not as clear in the two other species studied. Finally, the first evidence of relative photoreception in teleosts was obtained in cod suggesting that the definition of illuminance thresholds (day/night perception) would depend on the day intensity. Indeed, a single order of magnitude increase or decrease in day intensity was shown to elicit a significant shift in the intensity response curve of night-time melatonin suppression. Taken together, this study demonstrated species specific light intensity and spectral sensitivities within temperate teleosts.

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Differential light intensity and spectral sensitivities of Atlantic salmon, European sea bass and Atlantic cod pineal glands ex vivo

Abstract

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