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Deterioration of the Gαo vomeronasal pathway in sexually dimorphic mammals.

Suárez R, Fernández-Aburto P, Manger PR, Mpodozis J - PLoS ONE (2011)

Bottom Line: We noted that the species that lost the Gαo pathway belong to Laurasiatheria and Primates lineages, both clades with ubiquitous sexual dimorphisms across species.We found that both species show uniform expression of Gαi2-protein throughout AOB glomeruli, while Gαo expression is restricted to main olfactory glomeruli only.Our results suggest that the degeneration of the Gαo-expressing vomeronasal pathway has occurred independently at least four times in Eutheria, possibly related to the emergence of sexual dimorphisms and the ability of detecting the gender of conspecifics at distance.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Neurobiología y Biología del Conocer, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile. rsuarezsaa@gmail.com

ABSTRACT
In mammals, social and sexual behaviours are largely mediated by the vomeronasal system (VNS). The accessory olfactory bulb (AOB) is the first synaptic locus of the VNS and ranges from very large in Caviomorph rodents, small in carnivores and ungulates, to its complete absence in apes, elephants, most bats and aquatic species. Two pathways have been described in the VNS of mammals. In mice, vomeronasal neurons expressing Gαi2 protein project to the rostral portion of the AOB and respond mostly to small volatile molecules, whereas neurons expressing Gαo project to the caudal AOB and respond mostly to large non-volatile molecules. However, the Gαo-expressing pathway is absent in several species (horses, dogs, musk shrews, goats and marmosets) but no hypotheses have been proposed to date to explain the loss of that pathway. We noted that the species that lost the Gαo pathway belong to Laurasiatheria and Primates lineages, both clades with ubiquitous sexual dimorphisms across species. To assess whether similar events of Gαo pathway loss could have occurred convergently in dimorphic species we studied G-protein expression in the AOB of two species that independently evolved sexually dimorphic traits: the California ground squirrel Spermophilus beecheyi (Rodentia; Sciurognathi) and the cape hyrax Procavia capensis (Afrotheria; Hyracoidea). We found that both species show uniform expression of Gαi2-protein throughout AOB glomeruli, while Gαo expression is restricted to main olfactory glomeruli only. Our results suggest that the degeneration of the Gαo-expressing vomeronasal pathway has occurred independently at least four times in Eutheria, possibly related to the emergence of sexual dimorphisms and the ability of detecting the gender of conspecifics at distance.

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Sexual dimorphisms in Laurasiatheria and Primates.Males and females differ in body size and/or shape (A, elephant seal Mirounga leonina, Phocidae; B, lion Panthera leo, Felidae), presence of accessories such as horns or tusks (C, Impala Aepyceros melampus, Bovidae) and/or fur pattern/colouration (D, Gibbon Nomascus leucogenys, Hylobatidae). Pictures by Mike Baird (A), Vince Smith (B,C), and Linda Brosens (D) under a creative commons license.
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pone-0026436-g001: Sexual dimorphisms in Laurasiatheria and Primates.Males and females differ in body size and/or shape (A, elephant seal Mirounga leonina, Phocidae; B, lion Panthera leo, Felidae), presence of accessories such as horns or tusks (C, Impala Aepyceros melampus, Bovidae) and/or fur pattern/colouration (D, Gibbon Nomascus leucogenys, Hylobatidae). Pictures by Mike Baird (A), Vince Smith (B,C), and Linda Brosens (D) under a creative commons license.

Mentions: We noticed that practically all species of Primates and Laurasiatheres show visually conspicuous sexual dimorphisms, expressed not only in body size and shape but also in secondary traits such as hair/fur colouration patterns, the presence of accessories like horns or tusks, and behavioural displays (Fig. 1) [30], [31]. This observation prompted us to ask whether and to which extent the association between the absence of the Gαo-expressing pathway and the presence of sexual dimorphisms can be generalised among mammals.


Deterioration of the Gαo vomeronasal pathway in sexually dimorphic mammals.

Suárez R, Fernández-Aburto P, Manger PR, Mpodozis J - PLoS ONE (2011)

Sexual dimorphisms in Laurasiatheria and Primates.Males and females differ in body size and/or shape (A, elephant seal Mirounga leonina, Phocidae; B, lion Panthera leo, Felidae), presence of accessories such as horns or tusks (C, Impala Aepyceros melampus, Bovidae) and/or fur pattern/colouration (D, Gibbon Nomascus leucogenys, Hylobatidae). Pictures by Mike Baird (A), Vince Smith (B,C), and Linda Brosens (D) under a creative commons license.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3198400&req=5

pone-0026436-g001: Sexual dimorphisms in Laurasiatheria and Primates.Males and females differ in body size and/or shape (A, elephant seal Mirounga leonina, Phocidae; B, lion Panthera leo, Felidae), presence of accessories such as horns or tusks (C, Impala Aepyceros melampus, Bovidae) and/or fur pattern/colouration (D, Gibbon Nomascus leucogenys, Hylobatidae). Pictures by Mike Baird (A), Vince Smith (B,C), and Linda Brosens (D) under a creative commons license.
Mentions: We noticed that practically all species of Primates and Laurasiatheres show visually conspicuous sexual dimorphisms, expressed not only in body size and shape but also in secondary traits such as hair/fur colouration patterns, the presence of accessories like horns or tusks, and behavioural displays (Fig. 1) [30], [31]. This observation prompted us to ask whether and to which extent the association between the absence of the Gαo-expressing pathway and the presence of sexual dimorphisms can be generalised among mammals.

Bottom Line: We noted that the species that lost the Gαo pathway belong to Laurasiatheria and Primates lineages, both clades with ubiquitous sexual dimorphisms across species.We found that both species show uniform expression of Gαi2-protein throughout AOB glomeruli, while Gαo expression is restricted to main olfactory glomeruli only.Our results suggest that the degeneration of the Gαo-expressing vomeronasal pathway has occurred independently at least four times in Eutheria, possibly related to the emergence of sexual dimorphisms and the ability of detecting the gender of conspecifics at distance.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Neurobiología y Biología del Conocer, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago, Chile. rsuarezsaa@gmail.com

ABSTRACT
In mammals, social and sexual behaviours are largely mediated by the vomeronasal system (VNS). The accessory olfactory bulb (AOB) is the first synaptic locus of the VNS and ranges from very large in Caviomorph rodents, small in carnivores and ungulates, to its complete absence in apes, elephants, most bats and aquatic species. Two pathways have been described in the VNS of mammals. In mice, vomeronasal neurons expressing Gαi2 protein project to the rostral portion of the AOB and respond mostly to small volatile molecules, whereas neurons expressing Gαo project to the caudal AOB and respond mostly to large non-volatile molecules. However, the Gαo-expressing pathway is absent in several species (horses, dogs, musk shrews, goats and marmosets) but no hypotheses have been proposed to date to explain the loss of that pathway. We noted that the species that lost the Gαo pathway belong to Laurasiatheria and Primates lineages, both clades with ubiquitous sexual dimorphisms across species. To assess whether similar events of Gαo pathway loss could have occurred convergently in dimorphic species we studied G-protein expression in the AOB of two species that independently evolved sexually dimorphic traits: the California ground squirrel Spermophilus beecheyi (Rodentia; Sciurognathi) and the cape hyrax Procavia capensis (Afrotheria; Hyracoidea). We found that both species show uniform expression of Gαi2-protein throughout AOB glomeruli, while Gαo expression is restricted to main olfactory glomeruli only. Our results suggest that the degeneration of the Gαo-expressing vomeronasal pathway has occurred independently at least four times in Eutheria, possibly related to the emergence of sexual dimorphisms and the ability of detecting the gender of conspecifics at distance.

Show MeSH
Related in: MedlinePlus