Indeed, studies in terrestrial plethodontids have mainly focussed on pheromone delivery using the mental gland, while studies in aquatically reproducing salamandrids (newts) have concentrated on pheromones that are produced by the male dorsal glands. Īt first sight, specific glands and associated courtship strategies seem to be tied to particular evolutionary lineages. Whatever the exact manifestation, it seems that SPF is a pheromone system that has been able to influence female receptivity in a wide range of salamanders, probably since early urodelan evolution. In newts, it was shown that a single SPF-isoform was able to induce female following behaviour, which is one of the necessary prerequisites for successful insemination. In the plethodontid Desmognathus ocoee, behavioural experiments have shown that a fraction containing SPF proteins was able to reduce the duration of courtship. In both plethodontids and salamandrids, proteins of the sodefrin precursor-like factor (SPF) system have been identified as pheromones in the male sexually dimorphic glands. During courtship, newts open their cloaca to secrete pheromones, and some species additionally tail-fan towards the female for an optimal delivery. These glands are highly derived skin glands that are covering the caudal portion of the cloaca. In aquatically reproducing newts (Pleurodelinae, Salamandridae), males of several species develop sexually dimorphic glands in their cloaca, known as the dorsal cloacal glands a, which in some species extent into the pleuroperitoneal coeloem (also referred to as abdominal cavity). some Plethodon species), or transdermally by scratching the females’ dorsum (e.g. The secretions of this gland are either delivered through olfactory stimulation by slapping the females’ nostrils (e.g. For example, in many terrestrial reproducing lungless salamanders (Plethodontidae), the mental gland hypertrophies during the mating season. These displays often go together with the admission of pheromones from sexual dimorphic glands that develop during the breeding season. Salamanders (Urodela) are known to have a wide variety of courtship dances that males use to persuade females into mating. Since several male salamandrids in other genera have comparable head glands, SPF application via other glands than the cloacal glands may be more widespread than currently appreciated in salamandrids. The similar SPF expression of cheek and cloacal glands suggests that this protein family is used for pheromone signalling through cheek rubbing in the red-spotted newt. viridescens expresses a combination of isoforms that stem from four highly diverged evolutionary lineages of SPF variants, that together form a basis for the broad diversity of SPF precursors in the breeding glands. Expression in other tissues was much lower, suggesting that both male-specific courtship glands secrete SPF pheromones during courtship. viridescens produce a similar amount and diversity of SPF isoforms as the cloacal glands in this species. Our analyses indicate that the cheek glands of male N. Here we combined transcriptomic and phylogenetic analyses to investigate the presence, diversity and evolution of SPF proteins in the cloacal and cheek glands of this species. Males of red-spotted newts ( Notophthalmus viridescens, Salamandridae) have both cloacal and cheek (genial) glands, and are known to apply secretions to the female’s nose by both tail-fanning and cheek-rubbing. However, similar to plethodontids, some newts also make use of subtle head glands during courtship, but few pheromones have been characterized from such structures. In both families, sodefrin precursor-like factor (SPF) proteins have been identified as major components of the courtship pheromone system. The mental gland of lungless salamanders (Plethodontidae) and dorsal cloacal glands (or abdominal glands) of newts (Salamandridae) have been particularly well studied in that respect. Male salamanders (Urodela) often make use of pheromones that are produced in sexually dimorphic glands to persuade the female into courtship and mating.
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