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First published online November 17, 2005
Journal of Experimental Biology 208, 4391-4397 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01925

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Chromatic interaction between egg pigmentation and skin chromatophores in the nuptial coloration of female two-spotted gobies

Per Andreas Svensson^1,*, Elisabet Forsgren¹, Trond Amundsen¹ and Helen Nilsson Sköld²

¹ Department of Biology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
² Kristineberg Marine Research Station, Royal Swedish Academy of Science, 450 34 Fiskebäckskil, Sweden

^* Author for correspondence (e-mail: andreas.svensson{at}bio.ntnu.no)

Accepted 12 October 2005

In two-spotted gobies (Gobiusculus flavescens Fabricius 1779), females develop an orange belly as they approach sexual maturity. Bright belly coloration is preferred by males and has been suggested to act as a female ornament. This coloration is unusual in that it originates partly from pigmentation of the abdominal skin but also from strongly pigmented gonads directly visible through the skin. In addition, females have been observed to temporarily become more colourful during courtship and competition. To understand how gonad and skin pigmentation interact in this nuptial coloration, the potential for colour modification via regulation of skin chromatophores was investigated. Noradrenaline caused aggregation of chromatophore pigment and was used to experimentally reduce the contribution of skin chromatophores to the nuptial coloration. Chromatophore pigment aggregation caused bellies to become less colourful and abdominal skin biopsies to become less colourful and more transparent. There was a strong positive relationship between belly coloration and the coloration of the underlying gonads. This shows that belly coloration honestly reflects egg pigmentation, mainly because the transparency of the abdominal skin allows other fish to see the gonads directly. Interestingly, when noradrenaline caused pigment to aggregate and thereby increased the transparency of the skin, the relationship between belly and gonad coloration weakened. We conclude that female G. flavescens have a potential to use skin chromatophores to rapidly alter their nuptial coloration, thereby affecting the efficacy with which information about gonad coloration is conveyed.

Key words: sexual selection, nuptial signal, female ornament, courtship, Gobiusculus flavescens