NOTE / NOTE Sexual dichromatism in the marbled salamander, Ambystoma opacum

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 dor-sal 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 dimor-phic coloration in the ambystomatid salamander family, extending the known distribution of sexual dichromatism in the or-der Caudata. Résume ́ : On a rarement signale ́ le dichromatisme sexuel chez les salamandres et généralement seulement chez quelques espèces des familles Hynobiidae et Salamandridae. Nous avons utilise ́ des techniques d’analyse d’images pour étudier le dichromatisme sexuel chez la salamandre marbrée, Ambystoma opacum (Gravenhorst, 1807). Afin de déterminer l’impor-tance du dichromatisme sexuel chez les salamandres marbrées, nous avons mesure ́ la teinte moyenne des selles blanche