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Submitted by Edisangela Bastos (edisangela@ufpa.br) on 2013-03-05T21:17:38Z No. of bitstreams: 1 Dissertacao_DiversidadeEspeciesComplexo.pdf: 1354054 bytes, checksum: 488a49ce72ef48a66321024a1866b930 (MD5) / Approved for entry into archive by Ana Rosa Silva(arosa@ufpa.br) on 2013-03-11T14:42:32Z (GMT) No. of bitstreams: 1 Dissertacao_DiversidadeEspeciesComplexo.pdf: 1354054 bytes, checksum: 488a49ce72ef48a66321024a1866b930 (MD5) / Made available in DSpace on 2013-03-11T14:42:32Z (GMT). No. of bitstreams: 1 Dissertacao_DiversidadeEspeciesComplexo.pdf: 1354054 bytes, checksum: 488a49ce72ef48a66321024a1866b930 (MD5) Previous issue date: 2009 / O complexo de espécies M. brevicaudata possui distribuição reconhecida para o Norte da América do sul e compreende três espécies descritas ‐ M. brevicaudata, M. glirina, e M. palliolata ‐ e duas não descritas, reconhecidas em estudos prévios. A delimitação de espécies baseada somente em caracteres morfológicos é complicada, de forma que diversos táxons nominais já foram associados ao grupo e diversos arranjos taxonômicos foram propostos. Os poucos estudos baseados em dados moleculares que incluíram espécimes do complexo brevicaudata revelaram altas taxas de divergência genética. Este trabalho buscou elucidar a sistemática do complexo de espécies M. brevicaudata através do estudo dos padrões de variação morfológica e genética. Para tal, desenvolvemos análises filogenéticas baseadas em dois genes mitocondriais: citocromo b e 16 S rDNA. Adicionalmente, estudamos a morfologia externa e craniana dos espécimes, investigando a existência de congruência entre a variação genética e morfológica. As análises morfológicas foram, em geral, congruentes com as moleculares, as quais indicaram os mesmos clados em todas as análises filogenéticas. Foram formalmente reconhecidas nove espécies para o complexo. Monodelphis brevicaudata, M. palliolata e M. glirina são consideradas espécies válidas; M. touan é revalidado da sinonímia de M. brevicaudata e duas espécies novas são descritas e nomeadas; a espécie M. domestica provou ser intimamente relacionada a espécimes do grupo brevicaudata, sendo aqui considerada como integrante do referido grupo; duas espécies reconhecidas como distintas permanecem sem uma descrição formal; M. maraxina é sinonimizada com M. glirina. Foi observado dimorfismo sexual para as espécies estudadas, sendo que para as duas espécies estatisticamente testadas (teste T de student), M. glirina e M. sp. nov. “Trombetas”, os machos apresentaram crânios significativamente maiores que as fêmeas. Rios de grande porte parecem ter participado na diferenciação genética e estruturação filogeográfica das espécies. O padrão filogeográfico encontrado sugere ao menos dois centros de diversificação para o grupo, um no escudo das Guianas, envolvendo as espécies ao norte do rio Amazonas, e outro no escudo brasileiro, envolvendo M. glirina e M. domestica. / Short‐tailed opossums of the Monodelphis revicaudata complex inhabit northern South America, and comprise three described species ‐ M. brevicaudata, M. glirina, and M. palliolata ‐ and two undescribed forms already recognized in prior studies. Species delimitation based solely on morphological features is difficult, and because of that many nominal taxa have been associated with this species complex, and several taxonomic arrangements have been proposed. Previous molecular phylogenetic studies using specimens of this species complex revealed substantial genetic divergence rates. The present study aims to elucidate the systematics of the M. brevicaudata species complex through the analyses of molecular and morphological characters. We performed phylogenetic analyses on two mitochondrial genes (cyt b and 16S), studied the external and cranial morphology, and investigated whether observed genetic variation is congruent with morphological differences. Our morphological results were generally concordant with the molecular results. We recognize nine species in the species complex. M. brevicaudata, M. palliolata, and M. glirina are considered valid species; M. touan is re‐established from the synonymy of M. brevicaudata and two new species are described and named; the species M. domestica proved to be closely related to specimens of the M. brevicaudata complex, and thus are considered as part of that group; we also recognized two new species without formallly naming them; M. maraxina is considered a synonym of M. glirina. Sexual dimorphism is observed in the species, and in two species males showed skulls significantly larger than females. Major rivers seem to have played an important role in generating genetic differentiation and phylogeographical structure of the species. The phylogeographical pattern suggests at least two diversification centers for the group, one in the Guiana shield, comprising species ranging north of the Amazon river, and another in the Brazilian shield, comprising M. glirina and M. domestica.

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Les marsupiaux naissent très immatures, mais doivent atteindre une tétine, sans aide de la mère, à laquelle ils s’attachent pour poursuivre leur développement. Des informations sensorielles sont nécessaires pour s’orienter vers la tétine, la trouver, et s’y attacher. Le système vestibulaire, associé au sens de l’équilibre, a été proposé comme pouvant guider les petits marsupiaux vers la tétine en agissant sur les réseaux moteurs spinaux. Diverses études des marsupiaux suggèrent que le développement de ce système pourrait être suffisamment avancé pour influencer les comportements moteurs chez les nouveau-nés, mais son fonctionnement n’a jamais été testé. Pour le faire, nous avons soumis des opossums âgés de P0 (jour de la naissance; postnatal 0) à P21 à des stimulations vestibulaires et traité les tissus de la tête par immunohistochimie pour révéler c-Fos, utilisé comme indicateur d’activité neuronale. Du marquage dans les noyaux vestibulaires a été observé seulement à partir de P15. Pour confirmer ces résultats, nous avons effectué deux types d’expériences de stimulation sur des préparations in vitro d’opossums et enregistré les réponses motrices induites. Ainsi, des élévations de la tête n’ont pas permis de déceler de réponse suite aux stimulations aux âges étudiés (P4-P12). Par contraste, des pressions mécaniques directement appliquées sur le labyrinthe afin de stimuler les organes vestibulaires ont entrainé des réponses à tous les âges testés (P1-P9). Nos résultats suggèrent que la fonction du système vestibulaire est limitée par la maturité de ses organes sensoriels, et qu’il n’influence pas la motricité des nouveau-nés d’opossum en conditions physiologiques avant environ la fin de la 2e semaine de vie, même si les voies nerveuses entre les organes vestibulaires et la moelle épinière semblent déjà établies à la naissance. / Marsupials are born very immature, but must nevertheless find a teat, unaided by the mother, to which they attach to pursue their development. Sensory inputs are necessary to find the teat and attach to it, but the senses involved are still under discussion. The vestibular system, responsible for the sense of balance, was proposed as influencing motor behavior of newborns in various marsupial species by an action on spinal motor networks. Studies in the opossum Monodelphis domestica suggest that the development of the vestibular system could be advanced enough to influence locomotion at birth but its functionality has never been tested. To do that, we subjected intact opossums aged P0 (Postnatal day 0 ; day of birth) to P21 to vestibular stimulations and immunohistochemically processed their brain tissues to reveal c-Fos, used as a marker of neuronal activity. Immunoreactivity of neurons in the vestibular nuclei was observed only from P15 onwards. To confirm those results, we performed two series of experiments on in vitro preparations of newborn opossums, using stimulation of the vestibular apparatus and physiological recording of the induced motor responses Thus, vertical head tilts did not induce motor response at any of the ages studied (P4-P12). In contrast, mechanical pressure applied on the labyrinth to stimulate the vestibular organs induced motor responses at all ages studied (P1-P9). Our results suggest that the vestibular system’s function is limited by the maturity of its sensory organs and that it can’t influence motor activity in physiological condition before the end of the 2nd postnatal week, even if functional pathways from the labyrinth to the spinal cord seem to be already in place at birth.