Sexual dichromatism in the marbled salamander, Ambystoma opacum

Authors: Todd, Brian D.; Davis, Andrew K.

Source: Canadian Journal of Zoology, Volume 85, Number 9, September 2007 , pp. 1008-1013(6)

Publisher: NRC Research Press

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Abstract:

Reports of sexual dichromatism in salamanders are rare and have been generally restricted to a few species in the families Hynobiidae and Salamandridae. We used image analysis techniques to examine sexual dichromatism in the marbled salamander, Ambystoma opacum (Gravenhorst, 1807). We measured the average hue of white saddles on male and female marbled salamanders (n = 118), as well as the proportion of white dorsal surface area relative to the black dorsal surface area, to determine the extent of sexual dichromatism in this species. We also tested whether patterning and coloration were correlated with body size or relative body mass. Males had significantly whiter saddles and higher relative proportions of white coloration on their dorsal surfaces than did females. Furthermore, the relative proportion of white areas on the dorsum was positively correlated to body condition in both males and females. Body size was not correlated with hue or proportion of white area on the dorsum. To our knowledge, we report the first confirmation of sexually dimorphic coloration in the ambystomatid salamander family, extending the known distribution of sexual dichromatism in the order Caudata.

On a rarement signalé le dichromatisme sexuel chez les salamandres et généralement seulement chez quelques espèces des familles Hynobiidae et Salamandridae. Nous avons utilisé des techniques d'analyse d'images pour étudier le dichromatisme sexuel chez la salamandre marbrée, Ambystoma opacum (Gravenhorst, 1807). Afin de déterminer l'importance du dichromatisme sexuel chez les salamandres marbrées, nous avons mesuré la teinte moyenne des selles blanches sur les mâles et femelles (n = 118), ainsi que la proportion de surface blanche par rapport à la surface noire sur le dos. Nous avons vérifié si les patrons et la coloration sont en corrélation avec la taille corporelle ou la masse relative du corps. Par rapport aux femelles, les mâles possèdent des selles significativement plus blanches et une proportion relativement plus élevée de coloration blanche sur leur surface dorsale. De plus, la proportion relative des surfaces blanches sur le dos est en corrélation positive avec la condition corporelle tant chez les mâles que les femelles. La taille corporelle n'est reliée ni à la teinte, ni à la proportion de surface blanche dorsale. À notre connaissance, c'est la première fois qu'on signale une coloration sexuellement dimorphique chez des salamandres de la famille des ambystomatidés, ce qui élargit la répartition du dichromatisme sexuel dans l'ordre des Caudata.

Document Type: Research article

Publication date: 2007-09-01

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