South American Sigmodontine Research Articles

Parasites in micromammal fecal pellets throughout the Late Holocene ("Cueva Peligro" paleontological site, Patagonia, Argentina).

Parasite remains in micromammal fecal pellets collected from the paleontological site "Cueva Peligro" (CP 43°40'18"S, 66°24'52"W), Chubut Province, Argentina, were examined. The samples were obtained from two grids, dated between 1220±7014C yr B.P. to modern dates. Fecal pellets were whole processed, rehydrated, homogenized, and examined via light microscopy. Eggs of parasites found were measured and photographed. Fecal pellets belong to one or more insectivore to omnivore unidentified micromammal species, possibly sigmodontine rodents. A high number of helminthes species was recorded (11 species), eight nematodes, two anoplocephalid cestodes and one acanthocephalan species. The sigmodontine-parasite relationship varied throughout the studied period and between studied grids. This is the first time that Gongylonema sp. and Syphacia sp. are reported from ancient times from Patagonia. The obtained results contribute to the knowledge of parasite assemblages associated to native South American sigmodontine rodents and the zoonoses present in the area throughout the lasts 1200years.

Pattern of protein expression in the epididymis of Oligoryzomys nigripes (Cricetidae, Sigmodontinae).

In the epididymis, epithelial cells work in a concerted manner to create a luminal environment for sperm maturation, transport, and storage. However, the cell functions may be affected by anthropogenic factors, causing negative impacts on male fertility. In our study, we describe the pattern of protein expression in the epithelium and luminal fluid from epididymis of Oligoryzomys nigripes, a South American sigmodontine rodent whose reproductive biology has been little studied. Nine animals were captured from a preserved area of Atlantic Forest, where the exposure to anthropogenic influences is minimal. Epididymides were processed for histological analysis under light and epifluorescence microscopy, in which we used cell-specific markers aquaporin 9 (AQP9), vacuolar H+-ATPase (V-ATPase), and cytokeratin 5 (KRT5). Other samples were assessed for protein expression using shotgun proteomics. Similar to laboratory rodents, principal cells expressed AQP9 in their stereocilia. Basal cells, identified by KRT5 labeling, presented lateral body projections and a few axiopodia going toward the lumen. Clear cells expressed V-ATPase in their sub-apical vesicles and microplicae, and showed different shapes along the duct. Shotgun proteomics detected 51 proteins from epididymal supernatant. Most of them have been previously described in other species, indicating that they are well conserved. Twenty-three proteins detected in O. nigripes have not been described in epididymis from other South American sigmodontine rodents, confirming that the secretion pattern is species-specific. Our findings in O. nigripes from a protected area may help to create a baseline for studies investigating the effects of anthropogenic factors on functionality of the epididymal epithelium.

Proteomes and morphological features of Calomys tener and Necromys lasiurus (Cricetidae, Sigmodontinae) epididymides

Environmental factors, including exposure to anthropogenic factors such as endocrine disruptors, can affect the luminal fluid of the epididymides in which sperm reside during maturation, causing male reproductive dysfunction. We describe and compare epididymal morphology, histomorphometry, and proteomes of Calomystener and Necromys lasiurus, 2 species of South American sigmodontine rodent whose reproductive biology has been little studied. Five C. tener and 6 N. lasiurus were collected in a protected area of Atlantic Forest (Minas Gerais State, Brazil), where exposure to anthropogenic influences should be minimal. The left epididymis was processed for histological analysis under light microscopy, and the right was used to assess protein expression using shotgun proteomics. Calomys tener presented higher mean values for luminal and tubular diameters than N. lasiurus in the caput region. We observed similar morphologies and relative frequencies in the epididymal epithelium of principal, basal, and clear cells in the 2 species. Shotgun proteomics detected 58 and 64 proteins in 1 or more epididymal regions of C. tener and N. lasiurus, respectively. Aldose reductase, superoxide dismutase Cu-Zn, carboxylesterase 5A, and clusterin were only detected in the epididymis of N. lasiurus. The epididymides of C. tener and N. lasiurus differed in both histomorphometry and protein expression, suggesting that describing the epididymis in closely related species may provide a complementary tool for taxonomic studies. Knowledge of epididymal histophysiology helps establish a foundation for better understanding of the reproductive biology of these rodents, and our data from a protected area create a baseline for studies investigating the effects of environmental endocrine disruptors on functionality of the epididymal epithelium.

Geographical variation of body size in sigmodontine rodents depends on both environment and phylogenetic composition of communities

AbstractAimBody size variation in animal assemblages is a widely addressed pattern in biogeographical studies, and is affected by both environmental gradients and phylogenetic constraints. However, no study has yet explored to what extent the association between body size variation and environmental gradients across broad spatial scales is influenced by the biogeographical distribution of different phylogenetic lineages. In this study, we discriminate the influences of environmental variables and phylogenetic community composition on body size variation in South American sigmodontine rodents.LocationSouth America.MethodsWe computed the mean body mass of sigmodontine species co‐occurring in 1 × 1° cells across South America. For each cell we recorded mean values for three environmental variables. We characterized the phylogenetic composition of sigmodontine assemblages within each cell using phylogenetic fuzzy‐weighting and principal coordinates of phylogenetic structure (PCPS). We then partitioned out the influence of environmental factors and the phylogenetic community composition on mean body size.ResultsMean body size variation was mostly explained by shared influence of phylogenetic community composition (PCPS) and environmental factors (68%), while exclusive influence of PCPS was low (19%), and of environment was even lower (0.47%). Increases in body size were related to increases in annual mean temperature, and the influence of environment on body size was mediated by the distribution of sigmodontine lineages across South America.Main conclusionsEnvironment alone was not sufficient to explain body size variation in sigmodontine assemblages. Rather, environmental gradients interacted with historical processes to determine body size variation in the Neotropical assemblages. These results have implications for the way we think of body size gradients across species assemblages, because any gradient in a trait may be a result of differences in the biogeographical distribution of lineages across space, which should be considered in an explicit context.

Fur mites of the family Listrophoridae (Acariformes: Sarcoptoidea) associated with South American sigmodontine rodents (Cricetidae: Sigmodontinae)

Six species of 3 genera belonging to the fur mite family Listrophoridae were recorded on skins of South American rodents of the cricetid subfamily Sigmodontinae housed in the Bavarian State Collection of Zoology (Munich, Germany). Among them, Amlistrophorus geoxus sp. nov. from Geoxus valdivianus from Chile is described as a new for science, and males of Prolistrophorus amazonicus amazonicus Fain, 1971 are recorded for the first time. The full generic status for the subgenus Amlistrophorus of the genus Prolistrophorus proposed by Fain et al. (1996) is not supported, and Prolistrophorus musculinus Fain, 1973 stat. nov. (formerly a subspecies of P. amazonicus) from Mus musculus (Rodentia: Muridae) from Suriname is raised to species status. New hosts are recorded for the following species: Prolistrophorus argentinus (Hirst, 1921) from Holochilus brasiliensis and H. chacarius from Argentina, P. amazonicus from Calomys callosus from Argentina and Bolivia, C. laucha and C. musculinus from Argentina, P. akodon Fain and Lukoschus, 1982 from Akodon montensis from Argentina, P. nectomys Fain, 1971 from Nectomys palmipes from Peru and Melanomys caliginosus from Panama, and Sclerolistrophorus oxymycteris Fain, 1976 from Oryzomys laticeps from Brazil.

DNA sequence analysis and the phylogeographical history of the rodent Deltamys kempi (Sigmodontinae, Cricetidae) on the Atlantic Coastal Plain of south of Brazil

The rodent Deltamys kempiThomas, 1917 is found on the Coastal Plain - a recently formed geographic region located on Brazil's south-east coast. Considering that Deltamys is the only South American sigmodontine with a sex chromosome system of type X(1)X(1)X(2)X(2)/X(1)X(2)Y, this investigation was focused on the phylogeographic history of this taxon by using gene sequence analysis, trying to clarify when Deltamys differentiated, what was its centre of diversification, and what were the probable routes it used to reach its present distribution. We analysed sequences of the mitochondrial cytochrome b gene and nuclear recombination activating gene 2, performed cranial measurements and searched for centric fusions in individuals collected in distinct localities. The results, clearly demonstrate that D. kempi, on the Coastal Plain, divided into two groups, one occupying a small portion to the north of this region and the other spreading widely to the south. In this process, the phenomena of marine transgression and regressions which moulded its habitat, together with the occurrence of successive chromosomal rearrangements, were certainly the fundamental factors in shaping D. kempi diversification.

Phylogenetic and biogeographic relationships of gerbil mice Eligmodontia (Rodentia, Cricetidae) in South America, with a description of a new species

We present a systematic study of the genus Eligmodontia (sigmodontine rodents of the tribe Phyllotini) from Argentina, Bolivia, and Chile, based on molecular data. Phylogenetic relationships among 49 individuals were examined using nucleotide sequence data from the entire 1143 bp of the mitochondrial cytochrome-b gene. Unweighted parsimony, minimum evolution, maximum-likelihood (TrN+I+G), and Bayesian analyses revealed 2 major clades, representing Andean and non-Andean groups, and 6 minor clades, representing E. typus (lowland), E. typus (highland), E. morgani, E. puerulus, E. moreni, and E. hirtipes. E. typus (highland) is described as a new species based on combined data from the cytochrome-b gene, morphology, and karyology. The results indicate that the genus Eligmodontia is composed of a complex of species, most of which correspond to taxa that were described originally and each of which shows molecular cohesion within a limited geographic range. This species complex has relevance to current theories regarding the speciation patterns and the historical biogeography of South American sigmodontine rodents. The biogeographic history of the genus also is outlined.

New data on the endemic Patagonian long-clawed mouse Notiomys edwardsii (Rodentia: Cricetidae)

The monotypic Notiomys is the most poorly-known genus of Abrotrichini, a recently erected tribe of South American sigmodontine rodents. Based on a large sample, mostly recovered from owl pellets but including trapped individuals, we refine the known geographic distribution of this mouse (providing 20 new contemporary recording localities and four fossil occurrences), relate this to the principal Patagonian environmental units, add new data on the type locality of the species, and comment on its conservation status. In addition, we present a detailed external and craniodental description and provide data showing geographic variation of some skull features. Finally, we provide preliminary data on genetic variation (cytochrome b gene sequences) that demonstrate the existence of a low degree of observed differentiation (ca. 0.7%) between the populations analyzed.

Phylogenetic Relationships among Species of the Genus Calomys with Emphasis on South American Lowland Taxa

Abstract Calomys Waterhouse, 1837, is one of the most speciose genera of the Phyllotini tribe of the South American sigmodontine rodents. Distributed predominately in southern South America, the genus has been proposed to have originated in the central Andes with further differentiation as subsequent occupations of the lowlands of the continent occurred. In this study, 30 newly obtained sequences of the cytochrome-b gene from specimens collected in Brazil were analyzed in conjunction with data available in GenBank in an attempt to discern the dispersion patterns of this genus in the South American lowlands. The analyses support a scenario where a phyllotine lineage appeared in the Andes and later separated into 2 larger clades. Members of 1 clade remained in the highlands (C. musculinus, C. lepidus, and C. sorellus), experiencing some local differentiation. Members of the 2nd clade invaded the lowlands of South America, especially nonforested biomes, where they underwent intense differentiation resulting ...

Integrative taxonomy, systematics and distribution of the genus Eligmodontia (Rodentia, Cricetidae, Sigmodontinae) in the temperate Monte Desert of Argentina

The systematics and distribution of South American sigmodontine rodents a matter of continuous revision and debate. The silky mice, genus Eligmodontia Cuvier, 1837, are among the most specialized murid rodents endemic to South America and its diversification for desert existence is associated with the uplift of the Andes and the early development of arid landscapes. Aiming to clarify the systematics of the species of silky mice occurring in the driest portion of the temperate Monte Desert in Argentina, qualitative and quantitative external and cranial characters, cytogenetics and molecular relationships, were studied. We characterized three karyotypes of Eligmodontia; two of which are described for the first time, and allocated them to previously named species. E. moreni Thomas, 1896 (2 n=52 and FN=50), E. typus Cuvier, 1837 (2 n=44 and FN=44) and E. marica Thomas, 1918. The later shows the same diploid number of E. typus, but its X—chromosome is not METACENTRIC but ACROCENTRIC . A discriminant analysis of external and cranial data separates E. moreni from E. typus and E. marica. Whereas these last ones show some degree of overlap. The morphological and chromosomal differentiation of Eligmodontia is sustained by DNA distances. Phylogenetic analyses show two major clades. One formed by E. moreni, E. puerulus and E. hirtipes, sharing a high FN and a northern distribution, and THE other formed by E. typus, E. marica and E. morgani with low FN and a central-southern distribution. Two centers of diversification are proposed to explain the evolution of Eligmodontia.

Offspring sex-ratio and reproductive performance in heterogametic females of the South American field mouse Akodon azarae. Reproduction in heterogametic Akodon azarae females.

We have compared the breeding performance of homogametic (XX) and heterogametic (XY*) females of the South American sigmodontine rodent Akodon azarae under laboratory conditions. XY* females showed an enhanced reproductive performance when compared with normal, XX, females. The XY* females had a longer reproductive lifespan. They started to reproduce early, had more frequent litters, and stopped reproduction later than XX females. Their progeny showed a biased 1:2 male:female sex ratio which may be explained by the early loss of YY* zygotes after fertilization. However, litter size at birth was similar both in XY* and XX females, and no difference in ovulation rate was detected between them. This indicates that an "automatic" rather than an "evolved" reproductive compensation mechanism may be acting in heterogametic females. A separate study has shown that self-synapsis of both the X and Y* chromosomes takes place during meiosis, allowing the oocytes to escape from functional deterioration. It is suggested that self-synapsis and "automatic" reproductive compensation account for the preservation of fertility in heterogametic females in spite of the heteromorphic sex chromosomes and the early embryo loss they experience. However, these mechanisms do not account for the enhancement of reproductive lifespan. The possibility that an intrauterine position phenomenon is acting in A. azarae is discussed.

Testing models of diversification in mice in the Abrothrix olivaceus/xanthorhinus complex in Chile and Argentina.

Samples of the forest-dwelling mouse Abrothrix olivaceus and the steppe-dwelling A. xanthorhinus across a transect between 45 and 47 degrees S in southern Chile were analysed using the mitochondrial cytochrome b (cyt b) sequence, substantially adding to the data presented previously for these taxa from Argentina and Chile. The level of variation in the cyt b sequence throughout the entire olivaceus/xanthorhinus complex is comparable to that seen within a single species in many South American sigmodontine rodents, consistent with a previous conclusion that both taxa are sub-species of A. olivaceus. Haplotypes of xanthorhinus have not yet achieved reciprocal monophyly relative to those of olivaceus. We evaluate competing hypotheses for the morphological divergence of xanthorhinus and olivaceus by allopatry in Pleistocene refuges versus postglacial diversification across ecological gradients. Two contrasting patterns are predicted for plots of the distribution of pairwise genetic differences, depending on whether the taxa diverged in allopatric refuges or through selection across a gradient. Examples of both modes of diversification are found in this complex.

Phylogenetic Relationships and the Radiation of Sigmodontine Rodents in South America: Evidence from Cytochrome b

Phylogenetic relationships among South American sigmodontine rodents were examined based on the complete sequence for the mitochondrial cytochrome b gene [1140 base pairs (bp)] for 66 species and between 759 and 1140 bp for an additional 19 species. Thirty-eight South American genera were represented, coming from eight of nine tribes. Outgroups included the North American murid rodents Peromyscus, Reithrodontomys, Scotinomys, and Neotoma, the Old World murine rodents Mus and Rattus, and the geomyoid genera Thomomys, Geomys, Dipodomys, and Perognathus as the most distant outgroup. The South American sigmodontines were supported as a monophyletic lineage. Within this radiation several clear-cut suprageneric groupings were identified. Many of the currently recognized tribal groupings of genera were found fairly consistently, although not always with high levels of bootstrap support. The various tribes could not be linked hierarchically with any confidence. In addition, several genera stand out as unique entities, without any apparent close relatives. The overall pattern suggests a rapid radiation of the sigmodontines in South America, followed by differentiation at the tribal and generic levels.

Molecular Systematics and Paleobiogeography of the South American Sigmodontine Rodents

Molecular Systematics and Paleobiogeography of the South American Sigmodontine Rodents

Holarctic radiation of Neogene muroid rodents and the origin of South American cricetids

ABSTRACT A review of the fossil record suggests that Calomys (Bensonomys) may be derived from Megacricetodon from the Miocene of Eurasia. If this is true, South American sigmodontine cricetids could be less closely related to North American peromyscines than to some Old World muroids. An origin of Calomys (Bensonomys) from megacricetodontine ancestors is consistent with some neonto-logical approaches based on host–parasite distributions and penile morphology.