Cloacal gaping in females.

<p>The graphs represent female Relative Cloacal Gaping (RCG) at t₀ and t_max in courtship water and aged tap water (negative control). RCG was measured as the cloacal width (cw) divided by the tail base width (tb). The width of the cloaca was measured orthogonal to the center of the cloacal length (cl). The tail base was measured at the hind limb initiation region. If the cloaca was closed, RCG was set to 0.00.</p

Love Is Blind: Indiscriminate Female Mating Responses to Male Courtship Pheromones in Newts (Salamandridae)

<div><p>Internal fertilization without copulation or prolonged physical contact is a rare reproductive mode among vertebrates. In many newts (Salamandridae), the male deposits a spermatophore on the substrate in the water, which the female subsequently takes up with her cloaca. Because such an insemination requires intense coordination of both sexes, male newts have evolved a courtship display, essentially consisting of sending pheromones under water by tail-fanning towards their potential partner. Behavioral experiments until now mostly focused on an attractant function, i.e. showing that olfactory cues are able to bring both sexes together. However, since males start their display only after an initial contact phase, courtship pheromones are expected to have an alternative function. Here we developed a series of intraspecific and interspecific two-female experiments with alpine newt (<em>Ichthyosaura alpestris</em>) and palmate newt (<em>Lissotriton helveticus</em>) females, comparing behavior in male courtship water and control water. We show that male olfactory cues emitted during tail-fanning are pheromones that can induce all typical features of natural female mating behavior. Interestingly, females exposed to male pheromones of their own species show indiscriminate mating responses to conspecific and heterospecific females, indicating that visual cues are subordinate to olfactory cues during courtship.</p> </div

Results of the statistical tests.

<p>Ia = alpine newt male courtship water, MW = water in which non-courting alpine newt males had been kept, W = control water, Lh = palmate newt male courtship water, N = number of different females used in the experimental design. <i>P</i>-values smaller than 0.05 are considered significant and are indicated with an asterisk. The values for Kruskal-Wallis tests were as follows: intraspecific tests (<i>P_f</i><0.05, <i>P_tt</i><0.05 and <i>P_w</i><0.05), interspecific tests for alpine newt females (<i>P_f</i><0.05, <i>P_tt</i><0.05 and <i>P_w</i><0.05), interspecific tests for palmate newt females (<i>P_f</i><0.05, <i>P_tt</i><0.05 and <i>P_w</i> = 0.096).</p

Comparison of natural and experimental mating behavior.

<p>(<b>A</b>) <i>Female natural mating behavior:</i> the female follows the tail-waving male, touches the male's tail to stimulate spermatophore deposition, and uses tail-waving to encourage a male to continue courtship (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0056538#s2" target="_blank">Materials and methods</a>). (<b>B</b>) <i>Equivalent female behavior in a two-female experiment:</i> after addition of male courtship water, one female follows the other one, or both females try to follow each other; the following female regularly touches the tail of the other one; a female uses tail-waving in trying to encourage the other female.</p