Species Of Sigmodontine Rodents Research Articles

Assessing rodent community responses in disturbed environments of the Chilean Patagonia

AbstractThe effects of a perturbation gradient on a Patagonian rodent community were assessed over the course of a year by comparing the community parameters in natural and different disturbed environments in the central Chilean Patagonia. The studied habitat types were mature forest, second-growth forest, forest plantations, and agricultural grassland. We recorded eight species of sigmodontine rodents (

Similarities among ectoparasite fauna of sigmodontine rodents: phylogenetic and geographical influences

Phylogenetic and geographical overlaps in host distributions influence the compositional similarity of ectoparasite fauna in a host-parasite system. In these systems, hosts that are more closely related (phylogenetically) are expected to share more parasitic species than more distantly related hosts. Similarly, hosts sharing a larger geographical distribution overlap are expected to have similar ectoparasites. This study investigated the influence of phylogeny (divergence time) and geographical overlap of some neotropical sigmodontine rodent species on the similarities among their ectoparasite fauna (Mesostigmata and Siphonaptera), using a partial Mantel test. Divergence time was the only significant factor that influenced the similarity among the ectoparasites, when mites and fleas were analysed together. Host species that had diverged more recently displayed ectoparasite fauna that were similar. The similarities of the flea species showed similar results in both separate and joint analyses, but neither phylogenetic nor geographical overlap influenced the similarity in mite species. Fleas were shown to be more host-specific than were mesostigmate mites, probably because of the increased influence of host phylogeny.

Relationships of South American marsupials (Didelphimorphia, Microbiotheria and Paucituberculata) and hard ticks (Acari: Ixodidae) with distribution of four species of Ixodes

Historical information shows that South American marsupials are irrelevant hosts for South American hard ticks (Ixodidae Murray) of the genera Haemaphysalis Koch, Rhipicephalus Koch and Dermacentor Koch. Twenty two Amblyomma Koch species were occasionally found on Didelphimorphia Gill, but some records are doubtful (i.e., A. dissimile Koch, 1844) and only A. fuscum Neumann, 1907 appears to be a relevant parasite of this type of host. Twelve species of Ixodes Latreille were determined on these hosts, although one of them, I. longiscutatus Boero, 1944, is probably misidentified. Four species, I. amarali Fonseca, 1935b, I. loricatus Neumann, 1899, I. luciae Sénevet, 1940 and I. venezuelensis Kohls, 1953 are usual parasites of Didelphimorphia. These species (I. venezuelensis excluded) have adult ticks feeding mostly on Didelphidae Gray, and sub-adult ticks feeding mostly on Didelphidae and several species of sigmodontine rodents. All parasitic stages of I. venezuelensis were recorded from Didelphimorphia although rodents are also of importance for its life cycle. Records from marsupials and nonmarsupial hosts show that I. amarali is established in eastern Brazil, and I. venezuelensis in Venezuela, Colombia, Panama and Costa Rica. The alleged southernmost record of I. luciae in Central Argentina was found to be erroneous and its southern limit is located in northwestern Argentina and its way northwards includes Bolivia, Peru, western Brazil, French Guiana, Surinam, Trinidad & Tobago, Panama, Guatemala, Belize and southern Mexico with unconfirmed but probably valid records for Ecuador, Colombia, Costa Rica, Nicaragua and Honduras. The distribution of I. loricatus has been historically considered to range from southern Argentina to southern Mexico but southernmost and northernmost records are now considered doubtful along with Venezuelan populations for this tick, while the only records for Panama and Colombia were based on wrong tick identifications. Bona fide populations of I. loricatus range from central-eastern Argentina and southern Uruguay to Paraguay up to north-eastern Brazil. Dromiciops gliroides Thomas, the only member of Microbiotheria Ameghino is the exclusive host of Ixodes neuquenensis Ringuelet, 1947. There is only one record of tick infestation (Ixodes jonesae Kohls, Sonenshine & Clifford, 1969) of Paucituberculata Ameghino, indicating that these marsupials are of no apparent importance for maintenance of South American hard ticks. We speculate that the species of Ixodes feeding on Didelphimorphia and Sigmodontinae Wagner are a clade derived from ancestors feeding exclusively on Didelphidae that radiated after the invasion of South America by Sigmodontinae or their ancestors. Ixodes neuquenensis (established in south-western South America) is considered a relatively new species that radiated from Ixodes parasites of Sigmodontinae invaders in southern South America.

Descripción del postcráneo de Rhipidomys austrinus y Graomys griseoflavus (Rodentia, Cricetidae, Sigmodontinae)

Se describe el esqueleto postcraneal de dos especies de roedores sigmodontinos Rhipidomys austrinus Thomas, 1921 y Graomys griseoflavus (Waterhouse, 1837). Se detalla cada estructura del esqueleto postcraneal sobre la base de la forma, tamaño, superficie y orientación de cada elemento esqueletal. La anatomía postcraneal de estas dos especies muestra caracteres asociados a patrones morfológicos diferentes, vinculados a su modo de locomoción. Es así que R. austrinus exhibe características en varios elementos del postcráneo consistente con una locomoción arborícola, mientras G. griseoflavus muestra atributos en su esqueleto relacionados a una locomoción de tipo terrestre.

New Species of Trichuris (Nematoda: Trichuridae) from Akodon montensis Thomas, 1913, of the Paranaense Forest in Argentina

Species of Trichuris (Nematoda:Trichuridae) parasitize a broad range of mammalian hosts. To date, 21 Trichuris species infecting nine families of rodents have been found in North and South America. Trichuris navonae n. sp. is described on the basis of specimens recovered from a species of forest-dwelling mice, Akodon montensis (Cricetidae: Sigmodontinae), from nine localities of Misiones Province, Argentina. A comparison with all the species of Trichuris from North and South American rodents is given. The separation of the new species of Trichuris is based on morphologic and morphometrica features, such as the absence of a spicular tube, the presence of a cylindrical spicular sheath with sharp spines, a non-protrusive vulva, a long anterior-posterior portion of the body, a lengthy spicule, and a proximal and distal cloacal tube. This is the third record of this genus in rodents of the Sigmodontinae from Argentina and the fifth record from South American rodents. Despite the large number of potential host species, only about 1.9% of sigmodontine rodent species have been reported as hosts of Trichuris spp. It is suggested that this number represents but a small fraction of Trichuris spp. that occur in sigmodontine rodents, and that additional survey of this group should yield additional species.

Variation in cytochrome-b haplotypes suggests a new species of Zygodontomys (Rodentia: Cricetidae) endemic to Isla Coiba, Panama

The identity of two insular populations of rodents of the nominal species, Zygodontomys brevicauda (Allen & Chapman, 1893), from the Veragua Archipelago was examined. The mitochondrial cytochrome-b gene was sequenced from specimens collected on Isla Coiba (n = 10), Isla Cebaco (n = 3) and on the nearby Peninsula Azuero (n = 3) in Panama and compared with sequences of Z. brevicauda and a number of other related species from GenBank. For Panama, phylogenetic analyses identified two clades within Zygodontomys Allen, 1897; one representing Isla Coiba and another clade composed of rats from Isla Cebaco and from the mainland on the Peninsula Azuero, as well as a GenBank sequence of Z. brevicauda from Venezuela. We suggest that the population from Isla Coiba may represent a previously undescribed species of sigmodontine rodent that is endemic to this Pacific Island.

Genetic footprints of late Quaternary climate change in the diversity of Patagonian-Fueguian rodents

Species are impacted by climate change at both ecological and evolutionary time scales. Studies in northern continents have provided abundant evidence of dramatic shifts in distributions of species subsequent to the last glacial maximum (LGM), particularly at high latitudes. However, little is known about the history of southern continents, especially at high latitudes. South America is the only continent, other than Antarctica, that extends beyond 40 degrees S. Genetic studies of a few Patagonian species have provided seemingly conflicting results, indicating either postglacial colonization from restricted glacial refugia or persistence through glacial cycles and in situ differentiation. Using mitochondrial DNA sequences of 14 species of sigmodontine rodents, a major faunal ensemble of Patagonia and Tierra del Fuego, we show that at least nine of these species bear genetic footprints of demographic expansion from single restricted sources. However, timing of demographic expansion precedes the LGM in most of these species. Four species are fragmented phylogeographically within the region. Our results indicate that (i) demographic instability in response to historical climate change has been widespread in the Patagonian-Fueguian region, and is generally more pronounced at high latitudes in both southern and northern continents; (ii) colonization from lower latitudes is an important component of current Patagonian-Fueguian diversity; but (iii) in situ differentiation has also contributed to species diversity.

Mammalia, Rodentia, Sigmodontinae, Holochilus brasiliensis (Desmarest, 1819): distribution extention

We report the southernmost record for the marsh rats Holochilus brasiliensis 20 km S of Pedro Luro on Hwy 3, province of Buenos Aires, Argentina (39°41’31.13”S, 62°40’23.5”W) extending the range of the species ca. 110 km S. This represents the first contemporaneous record of H. brasiliensis in Patagonia, and also the only species of sigmodontine rodent with amphibious habits reported in Patagonia.

Host range and geographical distribution of Ixodes sigelos (Acari: Ixodidae)

Larvae, nymphs and females of Ixodes sigelos Keirans, Clifford and Corwin (Ixodidae) were collected in 13 localities of the Patagonian region of Argentina parasitizing eight species of sigmodontine rodents. We report for the first time adults of I. sigelos for Argentina. Besides, we extend the southern limit of its geographical distribution, and six species of sigmodontines are added as new host species of I. sigelos (Phyllotis xanthopygus, Euneomys chinchilloides, Calomys musculinus, Reithrodon auritus, Loxodontomys micropus and Eligmodontia morgani). The presence of larvae, nymphs and females on sigmodontines, as well as more than 50% of the individuals engorged, indicate that I. sigelos can develop the complete parasitic phase of its life cycle on these small mammals. The geographical distribution of I. sigelos is restricted to the biogeographical Andean Region in Argentina and Chile.

Genetic structure of sigmodontine rodents (Cricetidae) along an altitudinal gradient of the Atlantic Rain Forest in southern Brazil

The population genetic structure of two sympatric species of sigmodontine rodents (Oligoryzomys nigripes and Euryoryzomys russatus) was examined for mitochondrial DNA (mtDNA) sequence haplotypes of the control region. Samples were taken from three localities in the Atlantic Rain Forest in southern Brazil, along an altitudinal gradient with different types of habitat. In both species there was no genetic structure throughout their distribution, although levels of genetic variability and gene flow were high.

Diet of some species of Neotropical small mammals

Dietary analysis was performed to determine the variations in diet of some small neotropical species of mammals collected in seasonal areas of the cerrado (a savannah-like grassland) and semi-deciduous forest. Food items were determined based on the analysis of stomach contents of 126 animals (one didelphid and five sigmodontine rodent species). Most species presented herbivorous-omnivorous habits, with a preference for the vegetative parts of plants. Akodon montensis Thomas (1913) was the most abundant species in the forest area and demonstrated a uniform consumption of animal and vegetal items through the year, and contained 65.7% plant material in its diet. Necromys lasiurus (Lund, 1841) was the most abundant in the cerrado with 72.6% of vegetation in its diet, but showed a high consumption of animal items during the rainy season. Oligoryzomys nigripes (Olfers, 1818) contained 95.1% of plant material, while Oxymycterus delator (Thomas, 1903) consumed 61.6% invertebrates, mainly insects. The didelphid Philander frenatus (Olfers, 1818) consumed invertebrates (47.7%), small vertebrates (7.3%) and plant material (44.9%).

A new species of Juliomys (Mammalia: Rodentia: Cricetidae) from the Atlantic forest of southeastern Brazil

In the present paper, we describe Juliomys ossitenuis, a new species of sigmodontine rodent from the Altantic forest biodiversity hotspot in South America. This new species can be distinguished from the two congeners by clear morphological, molecular, and karyological characters. Juliomys ossitenuis is known from rain and semi-deciduous forests above 800 meters of altitude in southeastern Brazil, ranging from the state of Espírito Santo to São Paulo. Molecular phylogenetic analyses based on the mitochondrial cytochrome b gene confirmed that members of this new species form a well-supported monophyletic group, highly divergent from the other two species in the genus.

MOLECULAR PHYLOGEOGRAPHY OF ABROTHRIX OLIVACEUS (RODENTIA: SIGMODONTINAE) IN CHILE

Abrothrix olivaceus is the most abundant and widespread species of sigmodontine rodent in Chile. We evaluated phylogeographic relationships within A. olivaceous based on analyses of 67 specimens collected along most of the distributional range of the species. We used nucleotide sequence data from the hypervariable domain I of the mitochondrial DNA control region. Examination of our data supports a northern origin for this taxon, followed by southward dispersal. Also, we propose the occurrence of a new subspecies of A. olivaceus in the northernmost limit of the species' range. We detected a significant influence of recent paleoclimatic events on the current distribution of A. olivaceus, particularly in south-central Chile. The results also support the genetic distinctness of nominal subspecies proposed in the classical literature.

Rodent-associatedBartonellaFebrile Illness, Southwestern United States

Serum specimens from 114 patients hospitalized with a febrile illness were tested with an indirect immunofluorescence assay (IFA) using Bartonella antigens prepared from 6 species of sigmodontine rodents and 3 known human Bartonella pathogens: B. henselae, B. quintana, and B. elizabethae. Acute- and convalescent-phase serum samples from 5 of these patients showed seroconversion with an IFA titer >512 to rodent-associated Bartonella antigens. The highest titer was against antigen derived from the white-throated woodrat (Neotoma albigula), although this rodent is not necessarily implicated as the source of infection. Three of the 5 who seroconverted showed no cross-reaction to the 3 Bartonella human pathogens. Common clinical characteristics were fever, chills, myalgias, leukopenia, thrombocytopenia, and transaminasemia. Although antibodies to Bartonella are cross-reactive, high-titer seroconversions to rodent-associated Bartonella antigens in adults with common clinical characteristics should stimulate the search for additional Bartonella human pathogens.

Description of Adult and Fourth-Stage Larva of Litomosoides navonae n. sp. (Nematoda: Onchocercidae), a Parasite of Five Species of Sigmodontine Rodents from Northeastern Argentina

This study describes a new species of Litomosoides Chandler, 1931, parasitic in five different sigmodontine rodents from Misiones, Chaco and Formosa provinces of Argentina. The fourth-stage (L4) larva (male and female) is also described. L. navonae n. sp. exhibits: a bottle-shaped buccal cavity; a buccal capsule with irregularly crenate external walls; four externo-labial papillae and one ventral cephalic papilla; a well differentiated oesophagus; and sigmodontis-type spicules. The microfilaria is fusiform, with a large sheath. The L4 has a buccal capsule which is relatively longer than that of the adults, with narrower walls and a bottle-shaped lumen. It was observed in this species that the oesophagus/body-length ratio increases from larva to adult (female ratio 26.2-28.3 in larva; 88.4 in adults), and the vulva appears to move further posterior to the oesophago-intestinal junction (200-300 microm in larvae vs a mean of 600 microm in adults). L. navonae was found parasitising: Nectomys squamipes from the Reserve UNLP Valle del Arroyo Cuñá Pirú, Misiones; Oligoryzomys chacoensis, Holochilus chacarius and Akodon azarae bibianae from the marshes of Arroyo Bellaco, El Colorado, Formosa; and O. fornesi and H. chacarius from Selvas del Río de Oro (Chaco). Both N. squamipes and H. chacarius harbour other filarioids species, i.e. L. kohnae Bain, Petit & Diagne, 1989 and L. patersoni (Mazza, 1928), respectively, throughout their range, but these filarioids are readily differentiated from L. navonae. These well-differentiated filarial species found in Nectomys and Holochilus could indicate how isolated the populations of rodents are and could be interpreted either as: (a) an early point in the speciation processes that could be taking place in these hosts; or (b) extra support for the capture phenomenon theory of the evolution of Litomosoides. New regions, such as southern Brazil and northern Argentina, need to be studied in order to clarify these alternatives.

Molecular Evolution in Baiomys (Rodentia: Sigmodontinae): Evidence for a Genetic Subdivision in B. musculus

The genus Baiomys contains 2 extant species, the northern B. taylori and the southern B. musculus. Mitochondrial DNA sequences from the cytochrome-b gene were used to assess genetic variation within and between the 2 species. Samples of B. taylori and B. musculus each formed 2 separate clades and differed by an average sequence divergence of 11.62%. Average sequence divergence between the 2 clades of B. taylori was minimal (2.82%), whereas the value between the 2 clades of B. musculus was greater (6.46%). The level of genetic divergence between the clades of B. musculus is comparable to values seen between other sister species of sigmodontine rodents. The Trans-Mexican Volcanic Belt, Sierre Madre del Sur, and Rio Balsas may separate populations of B. musculus into northwestern and southern clades.

A new species of sigmodontine rodent from the Atlantic forest of eastern Brazil

We describe a new sigmodontine species on the basis of three specimens obtained from a high-altitude locality in the Atlantic forest of eastern Brazil. This new form, a small-bodied pentalophodont with tail longer than head and body, long soft fur, and a brownish ochraceous dorsum, is diagnosed by the presence of an open slit in the suture between the frontal bones in prepared skulls, and by a reduced diploid number of 20 coupled with a relatively high fundamental number of 34. Although the low diploid number suggests a derived sigmodontine, analyses of morphological characters and DNA sequence data (720 bp of the cytochrome-b gene) point to its placement within the recently described genusJuliomys Gonzalez, 2000, a taxon regarded as belonging to an old and independent sigmodontine lineage. This finding reinforces current hypotheses of the Atlantic forest domain as an important center of diversification for a primitive sigmodontine stock. It also suggests that at least some surviving lineages, often considered rather ancient and unspeciose relicts, were subject to relatively more recent speciation events.

Serologic evidence of hantavirus infection in sigmodontine rodents in Mexico.

Antibodies to hantaviruses in two species of sigmodontine rodents (Peromyscus maniculatus and Reithrodontomys sumichrasti) collected in central Mexico are reported. Peromyscus maniculatus, a common species throughout much of Mexico, is the reservoir of Sin Nombre virus (SNV), the etiologic agent of the great majority of cases of hantavirus pulmonary syndrome (HPS) in North America. Although the identity of the virus detected in P. maniculatus in Mexico could not be determined by these serologic results, our findings suggest that SNV may occur throughout the range of P. maniculatus in North America. If true, the failure to identify HPS in Mexico is not due to the absence of pathogenic hantaviruses in Mexico.

Microhabitat selection of five sigmodontine rodents in a forest-steppe transition zone in northwestern Patagonia

In a transition zone between Andean forests and Patagonian steppe, local populations of five sympatric species of sigmodontine rodents (Abrothrix longipilis, A. xanthorhinus, Eligmodontia morgani, Oligoryzomys longicaudatus, Reithrodon auritus) were examined for their microhabitat use. The study area represents a herbaceous steppe with sparse bushes. Over a four-year period, monthly samples were obtained by baited traps. The vegetation cover at each trapsite was monitored. The capture frequency in a particular microhabitat turned out to be strongly correlated with the local vegetation cover. This result is interpreted as a species-specific selection at a fine spatial scale of those microsites which resemble the characteristic environment in the area of main biogeographic occurrence of each of the rodents. The data on preferential microhabitat use might gather importance considering that two of these sigmodontine species are Hantavirus reservoirs.

Hantavirus reservoir hosts associated with peridomestic habitats in Argentina.

Five species of sigmodontine rodents have been identified in Argentina as the putative reservoirs of six circulating hantavirus genotypes. Two species of Oligoryzomys are associated with the genotypes causing hantavirus pulmonary syndrome, Oligoryzomys flavescens for Lechiguanas and O. longicaudatus for Andes and Oran genotypes. Reports of human cases of hantavirus pulmonary syndrome prompted rodent trapping (2,299 rodents of 32 species during 27,780 trap nights) at potential exposure sites in three disease-endemic areas. Antibody reactive to Sin Nombre virus was found in six species, including the known hantavirus reservoir species. Risk for peridomestic exposure to host species that carry recognized human pathogens was high in all three major disease-endemic areas.