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

Abstract

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 (Ichthyosaura alpestris) and palmate newt (Lissotriton helveticus) 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.

Seasonal variation in environmental DNA in relation to population size and environmental factors

“…During the breeding season newts expend energy in courtship and reproduction, releasing pheromones4647, spermatophores and eggs into the environment, all potentially directly or indirectly releasing DNA with them. The release of these products into the environment will not only lead to an increase in eDNA but it will reduce the mass of an individual and lead to a reduction in body condition.…”

The use of bioacoustics in anuran taxonomy: theory, terminology, methods and recommendations for best practice

“…Evidence for reproductive isolation can be found through a variety of approaches, including postzygotic hybrid inviability, divergent morphological structure of genitals, or differences in behavioral characters mediating mate recognition. In amphibians, mechanisms of mate recognition and mate choice involve pheromones in salamanders and frogs (Malacarne & Giacoma 1986;Pearl et al 2000;Toyoda et al 2004;Kikuyama et al 2005;Byrne & Keogh 2007;Belanger & Corkum 2009;Poth et al 2012;Starnberger et al 2013;Treer et al 2013), visual signaling such as foot-waving (Hödl & Amézquita 2001;Toledo et al 2007;Boeckle et al 2009), elaborated nuptial displays in newts (Halliday 1977) or inflation of, sometimes colorful, vocal sacs (e.g., Rosenthal et al 2004;Hirschmann & Hödl 2006), water surface waves (Walkowiak & Münz 1985), surface vibrations (Narins 1990;Cardoso & Heyer 1995;Lewis et al 2001;Caldwell et al 2010), acoustic signals (most Sampling rate (R) Number of amplitude measurements taken per second when digitizing a sound wave (e.g., 44.1 kHz sampling rate results in 44,100 samples of amplitude measurement for every second).…”

Size does not matter for male Marbled Salamanders (Ambystomaopacum)

“…Of course, it remains possible that phenotypic variation in any of a number of additional traits could influence the fitness variance we observed. For example, arrival time at the breeding site, courtship interference, female mimicry, pheromone production, genetic compatibility, sperm competition, or some other morphological trait may play a role (Arnold 1976;Garner and Schmidt 2003;Tennessen and Zamudio 2003;Treer et al 2013). The lack of an effect shown here and mixed results offered by the few available data in other species highlight the need for more sexual selection studies to determine the factors that influence fitness variance in salamanders.…”