Ornamentation and Characteristics of the Tail in the Male Guppy
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- Institutt for biologi 
Male guppies (Poecilia reticulata) show great variation in both shape and coloration of the caudal fin. In some males, an elongation of the caudal fin is present, referred to as a sword. This thesis will mainly focus on the sword and how it is related to other properties in the male guppy. Here, the first part is a description of the sword. Then we analyze allometric relationship of different sexual traits, including the sword, and their correlations. We then test whether sworded and non-sworded males differ in terms of their characteristics and the ones of their offspring. Finally, we estimate the heritability of the different traits. Our results show that the caudal fin length (excluding the sword) and the gonopodium length both present negative allometry and are correlated. On the other hand , sword length and the length of the color length of the caudal fin do not show any relationship to standard length. However, the sword is always associated with a color band. Sworded males differ from non-sworded males in that they have a smaller body size but a larger total tail length, and they also sire offspring with different characteristics of their caudal fin. Furthermore, while we generally found substantially genetic variation in the studied sexual traits, the sword length did not seem to harbor any genetic variation.