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Endocrine control of skin colour - the role of stress

The MSH release mechanisms from the pituitary of both wild and reared red porgy was identified. Dopamine (DA) and Melanocyte-concentrating hormone (MCH) have an inhibitory effect on the release of MSH from the pituitary of red porgy.

DA shows a biphasic response, in which the 10{-11} concentration has a slightly stimulatory effect while the other concentrations are inhibitory. The concentrations measured in wild fish show a similar response. MCH shows an inhibition of the release at all concentrations except at very low concentrations, when no response is visible. Wild fish pituitaries show a similar range of inhibition. CRH has no effect at most concentrations, except for very high concentrations when a strong stimulatory effect can be observed. In wild fish, the effects are exactly the same. TRH shows stimulation at all concentrations tested. At low concentrations, this effect is fairly small, while at high concentrations a strong stimulatory effect is visible.

A similar result was obtained with the concentrations tested for wild fish. However, in wild fish the effect is about 40-50% lower than in cultured fish. For all secretagogues tested and for both the highest and lowest concentrations, mono-acetylated á-MSH was the dominant form.

Concerning the role of husbandry stress on skin colour results show that there was no significant effect of background colour, lighting spectrum & intensity and stocking density on the circulating stress indicators determined (cortisol, áMSH, glucose, lactate, osmolality, electrolytes). In addition, there was no correlation between chromaticity parameters and the used stress indexes.

Reported by

Katholieke Universiteit Nijmegen
Toernooiveld 1
6500 GL Nijmegen
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