Mosaic Convergence of Rodent Dentitions

BACKGROUND:Understanding mechanisms responsible for changes in tooth morphology in the course of evolution is an area of investigation common to both paleontology and developmental biology. Detailed analyses of molar tooth crown shape have shown frequent homoplasia in mammalian evolution, which requires accurate investigation of the evolutionary pathways provided by the fossil record. The necessity of preservation of an effective occlusion has been hypothesized to functionally constrain crown morphological changes and to also facilitate convergent evolution. The Muroidea superfamily constitutes a relevant model for the study of molar crown diversification because it encompasses one third of the extant mammalian biodiversity. METHODOLOGY/PRINCIPAL FINDINGS:Combined microwear and 3D-topographic analyses performed on fossil and extant muroid molars allow for a first quantification of the relationships between changes in crown morphology and functionality of occlusion. Based on an abundant fossil record and on a well resolved phylogeny, our results show that the most derived functional condition associates longitudinal chewing and non interlocking of cusps. This condition has been reached at least 7 times within muroids via two main types of evolutionary pathways each respecting functional continuity. In the first type, the flattening of tooth crown which induces the removal of cusp interlocking occurs before the rotation of the chewing movement. In the second type however, flattening is subsequent to rotation of the chewing movement which can be associated with certain changes in cusp morphology. CONCLUSION/SIGNIFICANCE:The reverse orders of the changes involved in these different pathways reveal a mosaic evolution of mammalian dentition in which direction of chewing and crown shape seem to be partly decoupled. Either can change in respect to strong functional constraints affecting occlusion which thereby limit the number of the possible pathways. Because convergent pathways imply distinct ontogenetic trajectories, new Evo/Devo comparative studies on cusp morphogenesis are necessary

Glial cell type-specific changes in spinal dipeptidyl peptidase 4 expression and effects of its inhibitors in inflammatory and neuropatic pain

Altered pain sensations such as hyperalgesia and allodynia are characteristic features of various pain states, and remain difficult to treat. We have shown previously that spinal application of dipeptidyl peptidase 4 (DPP4) inhibitors induces strong antihyperalgesic effect during inflammatory pain. In this study we observed low level of DPP4 mRNA in the rat spinal dorsal horn in physiological conditions, which did not change significantly either in carrageenan-induced inflammatory or partial nerve ligation-generated neuropathic states. In naive animals, microglia and astrocytes expressed DPP4 protein with one and two orders of magnitude higher than neurons, respectively. DPP4 significantly increased in astrocytes during inflammation and in microglia in neuropathy. Intrathecal application of two DPP4 inhibitors tripeptide isoleucin-prolin-isoleucin (IPI) and the antidiabetic drug vildagliptin resulted in robust opioid-dependent antihyperalgesic effect during inflammation, and milder but significant opioid-independent antihyperalgesic action in the neuropathic model. The opioid-mediated antihyperalgesic effect of IPI was exclusively related to mu-opioid receptors, while vildagliptin affected mainly delta-receptor activity, although mu- and kappa-receptors were also involved. None of the inhibitors influenced allodynia. Our results suggest pathology and glia-type specific changes of DPP4 activity in the spinal cord, which contribute to the development and maintenance of hyperalgesia and interact with endogenous opioid systems

Contributions in honor of Guy G. Musser.

450 p. : ill. (some col.), maps ; 26 cm. "Issued December 15, 2009." Includes bibliographical references.Contents: They sort out like nuts and bolts : a scientific biography of Guy G. Musser / Michael D. Carleton -- Taxonomy, distribution, and natural history of the genus Heteromys ‪(‬Rodentia: Heteromyidae‪)‬ in central and eastern Venezuela, with the description of a new species from the Cordillera de la Costa / Robert P. Anderson and Eliécer E. Gutiérrez -- Review of the Oryzomys couesi complex ‪(‬Rodentia: Cricetidae: Sigmodontinae‪)‬ in western Mexico / Michael D. Carleton and Joaquin Arroyo-Cabrales -- The antiquity of Rhizomys and independent acquisition of fossorial traits in subterranean muroids / Lawrence J. Flynn -- A new species of Reithrodontomys, subgenus Aporodon ‪(‬Cricetidae: Neotominae‪)‬, from the highlands of Costa Rica, with comments on Costa Rican and Panamanian Reithrodontomys / Alfred L. Gardner and Michael D. Carleton -- Phylogenetic relationships of harpyionycterine megabats ‪(‬Chiroptera: Pteropodidae‪)‬ / Norberto P. Giannini, Francisca Cunha Almeida, and Nancy B. Simmons -- A new genus and species of small ‪"‬tree-mouse‪"‬ ‪(‬Rodentia, Muridae‪)‬ related to the Philippine giant cloud rats / Lawrence R. Heaney, Danilo S. Balete, Eric A. Rickart, M. Josefa Veluz, and Sharon A. Jansa -- Biodiversity and biogeography of the moss-mice of New Guinea : a taxonomic revision of Pseudohydromys ‪(‬Muridae: Murinae‪)‬ / Kristofer M. Helgen and Lauren E. Helgen -- Systematic revision of sub-Saharan African dormice ‪(‬Rodentia: Gliridae‪)‬. Part 2, Description of a new species of Graphiurus from the central Congo Basin, including morphological and ecological niche comparisons with G. crassicaudatus and G. lorraineus / Mary Ellen Holden and Rebecca S. Levine -- Descriptions of new species of Crocidura ‪(‬Soricomorpha: Soricidae‪)‬ from mainland Southeast Asia, with synopses of previously described species and remarks on biogeography / Paulina D. Jenkins, Darrin P. Lunde, and Clive B. Moncrieff -- The six opossums of Félix de Azara : identification, taxonomic history, neotype designations, and nomenclatural recommendations / Robert S. Voss, Philip Myers, François Catzeflis, Ana Paula Carmignotto, and Josefina Barreiro -- Skull and dentition of Willeumys korthi, nov. gen. et sp., a cricetid rodent from the Oligocene ‪(‬Orellan‪)‬ of Wyoming / John H. Wahlert

Locomotory adaptations in entoptychine gophers (Rodentia: Geomyidae) and the mosaic evolution of fossoriality

Pocket gophers (family Geomyidae) are the dominant burrowing rodents in North America today. Their fossil record is also incredibly rich; in particular, entoptychine gophers, a diverse extinct subfamily of the Geomyidae, are known from countless teeth and jaws from Oligocene and Miocene-aged deposits of the western United States and Mexico. Their postcranial remains, however, are much rarer and little studied. Yet, they offer the opportunity to investigate the locomotion of fossil gophers, shed light on the evolution of fossoriality, and enable ecomorphological comparisons with contemporaneous rodents. We present herein a quantitative study of the cranial and postcranial remains of eight different species of entoptychine gophers as well as many contemporary rodent species. We find a range of burrowing capabilities within Entoptychinae, including semifossorial scratch-digging animals and fossorial taxa with cranial adaptations to burrowing. Our results suggest the repeated evolution of chisel-tooth digging across genera. Comparisons between entoptychine gophers and contemporaneous rodent taxa show little ecomorphological overlap and suggest that the succession of burrowing rodent taxa on the landscape may have had more to do with habitat partitioning than competition

Molecular systematics of dormice (Rodentia: Gliridae) and the radiation of Graphiurus in Africa.

The phylogenetic relationships among the Gliridae (order Rodentia) were assessed using 3430 nucleotides derived from three nuclear fragments (beta-spectrin non-erythrocytic 1, thyrotropin and lecithin cholesterol acyl transferase) and one mitochondrial gene (12S rRNA). We included 14 glirid species, representative of seven genera of the three recognized subfamilies (Graphiurinae, Glirinae and Leithiinae) in our analysis. The molecular data identified three evolutionary lineages that broadly correspond to the three extant subfamilies. However, the data suggest that the genus Muscardinus, previously regarded as falling within the Glirinae, should be included in the Leithiinae. Molecular dating using local molecular clocks and partitioned datasets allowed an estimate of the timing of cladogenesis within the glirids. Graphiurus probably diverged early in the group's evolution (40-50 Myr ago) and the three subfamilies diverged contemporaneously, probably in Europe. The radiation within Graphiurus is more recent, with the colonization of Africa by this lineage estimated at ca. 8-10 Myr ago