Showing papers on "Sigmodontinae published in 2019"

A new species of Oxymycterus (Rodentia: Cricetidae: Sigmodontinae) from a transitional area of Cerrado – Atlantic Forest in southeastern Brazil

Abstract: We describe a new species of the cricetid rodent Oxymycterus (Sigmodontinae), which inhabits a transitional area between the southern Cerrado and the Atlantic Forest in south-southeastern Brazil. Compared to other Oxymycterus, the new species is large-sized with a tawny-brown pelage coloration. The new species could be differentiated from other Oxymycterus species by a combination of cranial characteristics that includes markedly large and inflated auditory bulla; a narrow rostrum and large incisive foramen, with the posterior extremity reaching the posterior region of the M1 protocone or hypoflexus; a wide parapterygoid fossa; the presence of a foramen ovale in the posterior region of the parapterygoid plate; and a thin hamular process of the squamosal. Bayesian analysis based on the mitochondrial and nuclear genes (cytochrome-b and acid phosphatase type V—Intron 2, respectively) recovered from the Oxymycterus sp. nov. showed it to be phylogenetically closely related to O. amazonicus and O. delator, all three species associated with open vegetation. The lineage leading to this clade likely emerged around 1.14 million years ago during the Early-Middle Pleistocene. Genetic distances between the new taxa and these two species calculated from comparison of cytochrome-b sequences are 3.7% and 4.1%, respectively. Currently, Oxymycterus sp. nov. is known from only two unprotected sites, with the type locality inserted in an area under the process of conurbation. Our study raises the number of living species in the genus to 16.

The oldest sigmodontine rodent revisited and the age of the first South American cricetids

Abstract: New fossil material of Auliscomys formosus Reig 1978 allows restudy of the oldest known South American representative of the subfamily Sigmodontinae. Description of Auliscomys formosus was based on a fragmentary dentary exhumed from the Monte Hermoso Formation of central Argentina. Previous studies allocated A. formosus to the early Pliocene. A reevaluation of dental and cranial morphology, including for the first time the upper dentition, and the inclusion of A. formosus in a phylogenetic analysis of the tribe Phyllotini indicate that A. formosus represents a new genus, Kraglievichimys. Kraglievichimys shares a mosaic of characters with the living Auliscomys Osgood, 1915 and Loxodontomys Osgood, 1947. The taxonomic reassignment of A. formosus and the possibility that the Monte Hermoso Formation may be younger than early Pliocene in age provide a new understanding of cricetid diversification in South America. Estimates of sigmodontine ancestry by molecular approaches are biased toward older ages, whereas this new interpretation of the history of K. formosus suggests that the South American history of sigmodontines spans less than 4 million years.UUID: http://zoobank.org/49dd8f60-56b1-4e8a-a044-6cea3a1bd52b

Movement and use of environmental structures, climbing supports and shelters by Akodon montensis (Sigmodontinae, Rodentia) in the Atlantic Forest of southern Brazil

Abstract: Abstract Movements under environmental structures and on supports, and the use of shelters by Akodon montensis were assessed using the spool-and-line technique. Movements of a few individuals of Thaptomys nigrita, Brucepattersonius iheringi and Oligoryzomys nigripes were also assessed and briefly described. Akodon montensis often used fallen logs, lianas and ferns as climbing supports for movements. The species moved under different environmental structures with differing frequencies, with greater use of dense litter followed by lianas and fallen branches. The studied sigmodontine species used shelters of different compositions and structures, and differed in displacement behavior. This study is the first to contribute to understanding the movement and use of environmental structures, shelters and climbing supports by A. montensis.

Nematode Parasites of Rodents (Sigmodontinae) and Update of Those Recorded in Other Wild Mammals from Costa Rica

Abstract: Between June 1998 and July 1999, 3 Alfaro's rice rats (Handleyomys alfaroi) and 3 Bolivar rice rats (Transandinomys bolivaris) from the Area de Conservacion Guanacaste, Costa Rica, were examined for parasites. Adult nematodes representing 4 taxa were collected: Physaloptera calnuensis, Stilestrongylus hidalguensis, and Syphacia sp. (from H. alfaroi) and in T. bolivaris. This report represents the first record for P. calnuensis and S. hidalguensis in Costa Rica; furthermore, this is the first time these helminths have been documented infecting H. alfaroi and T. bolivaris. Based on this study and in the compilation of information related to the nematodes described in wild Costa Rican mammals, we determined that 68 helminth taxa have been registered so far (35 named species and 33 taxa) parasitizing 29 species of mammals.

Mesial hyperdontia in Sigmodontinae (Rodentia: Cricetidae), with comments on the evolution of the anteroconid in Myomorpha

Abstract: Abstract Supernumerary teeth are common dental anomalies reported in rodents, mainly occurring distally to molars. We report the first case of mesial hyperdontia in wild-caught sigmodontine: a simplified tooth anterior to the right first lower molar in Neacomys amoenus. It affected the first molar morphology, which exhibits an underdeveloped mesial region with a reduced anterior conulid, a similar pattern observed in early known myomorph fossils, including lineages that still possess the last premolar. However, only lineages without premolar display an elongated first lower molar with a large anteroconid, as observed in extant Myomorpha. During the odontogenesis in myomorphs, the posteriormost vestigial diastemal tooth bud, located at the same locus of the last lower premolar, has its development arrested and merges with the cap of the first molar. This process might have contributed to the development of an increased anteroconid in this lineage. The abnormal Neacomys’ atavistic phenotype corroborates the hypothesis that the absorption of the primordium of the last lower premolar had played an important role in the development of first molar’s mesial region. Additionally, it also might have promoted the evolutionary transition from a reduced conulid into an enlarged anteroconid, as deduced from the fossil record and developmental evidence

Calodium hepaticum (Trichuroidea: Capillariidae) Infection in Akodon azarae: First Description of Histopathological Lesions in Sigmodontinae

Abstract: Calodium hepaticum (Trichinellida: Capillaridae) is a parasitic nematode of mammals distributed worldwide. Although this parasite can infect the liver of a wide diversity of mammals (including humans), it is mostly associated with Muroidea hosts. Sigmodontinae rodents were recently recognized as important hosts of this parasite in Argentina, but the impact of this parasitism on these hosts has not been established. Here we report results of histopathological analyses of 40 livers of Akodon azarae infected with C. hepaticum. Lesions were classified into 4 categories: level 0, absence of lesions; level 1, with focal granulomatous hepatitis; level 2, presence of multifocal granulomatous hepatitis, fibrosis and focal necrosis with neutrophils, and level 3, absence of intact adult parasites, diffuse distribution, necrosis, and fibrosis. Most samples presented lesions of level 2 (55%), but all categories of lesions were found. This is the first study to describe the lesions caused by C. hepaticum in the liver of Sigmodontinae rodents, and the results suggest that infection by this parasite is costly to A. azarae populations.

First record of the Santa Marta mouse, Nephelomys maculiventer (Mammalia, Rodentia, Cricetidae), for Venezuela

Abstract: Abstract We report the first record of the Santa Marta mouse Nephelomys maculiventer in Venezuela based on a specimen from the Northern Andes in the Sierra de Perijá. This record increases the number of mammalian species documented in Venezuela to 404 and extends the geographic distribution range of N. maculiventer approximately 80 km northwest from the closest locality in Colombia. With this discovery, we update the ecological and conservation information for the species as well as the taxonomy of the genus Nephelomys.

A new species of Sigmodontinae (Rodentia) from the late Hemphillian of central Mexico, and comments on the possible radiation of this group

Abstract: The Sigmodontinae subfamily represents one of the most diverse groups of mammals in the world; this rodent group evolved in the open and arid ecosystems of the Miocene of North America and was the most successful legion of mammals in the Great American Biotic Interchange. Part of its diversification occurred in the Mexican Pliocene, in the Hemphillian-Blancan boundary, where Prosigmodon and Sigmodon species are very common. Recent molecular phylogenetic systematics research proposes that Sigmodon is related to South American sigmodontines, while studies of classical morphometry in isolated molar teeth consider Prosigmodon as a junior synonymy of Sigmodon, which modifies the biogeographic and chronostratigraphic interpretations of this group in America. In this paper, we describe a new species of Prosigmodon from the late Hemphillian (~4.89 Ma) of central Mexico based on jaws, maxillary and complete isolated teeth. This is the most complete and austral record of the genus in North America. This species was compared with North American species of the Sigmodontinae and Neotominae subfamilies and we defined it as a new Prosigmodon species characterized by having a consistently present minute mesoloph in M1 and M2, in addition, there is an isolated metaconid from the protoconid in the m1 of young individuals. We performed a phylogenetic model using osteodental morphological characters focused on understanding the relationship between Prosigmodon (four species) and Sigmodon (eight species), also we included Baiomys (two species), Neotoma (two species), Peromyscus (two species), and Reithrodontomys (two species). Our results indicate that Prosigmodon is a monophyletic group if Sigmodon minor is included within the genus and P. chihuahuensis is excluded. The Mexican Prosigmodon species have more apomorphic characters with respect to S. minor and P. holocuspis. The species of Prosigmodon and Sigmodon are not closely related. The Sigmodon species are more closely related to the Neotoma species than to the species of Baiomys, Prosigmodon, Reithrodontomys and Peromyscus. Based on the topology of our cladogram and the stratigraphic ranges of the species of Sigmodontinae and Neotominae, we discuss that Baiomys, Prosigmodon, Reithrodontomys and Peromyscus probably diversified in the early Hemphillian (late Miocene), while Sigmodon and Neotoma did so during the late Pliocene.

Does the widely distributed rodent Calomys tener (Cricetidae: Sigmodontinae) constitute a single evolutionary unit?

Abstract: The nominal species Calomys tener (Winge, 1887) ranges broadly in open lands of the Caatinga, Cerrado, Pantanal and Mata Atlântica of Brazil, and was recently reported from the Pampas of southern Brazil, and in the Selva Paranaense of eastern Paraguay and northeastern Argentina. This rodent can be infected with the pathogenic Araraquara hantavirus in Brazil. Given that most epidemiological studies have not taken into account updated taxonomic findings of their rodent hosts, in this study, we obtained sequence data of the Cyt-b and COI genes of specimens of C. tener from 22 different geographical localities from throughout the currently known distribution of the species (including individuals from Argentina, Paraguay, Bolivia, and Brazil) to test if it constitutes a single genetic unit or if it presents genetic discontinuities that may represent different evolutionary lineages. Phylogenetic analyses including several species of Calomys recovered several clades with strong support. Regarding C. tener, it is recovered as sister to the node that cluster C. laucha (Fischer, 1814) sensu lato, C. expulsus (Lund, 1841) and species in the C. callosus (Rengger, 1830) species complex. At the intraspecific level there are no genetic gaps among haplotypes of C. tener that could suggest more than one species. The recent captures in the Pampas of southern Brazil and in the Selva Paranaense suggest that the species may be colonizing new geographic areas.