Blarinomys Research Articles

Identification of mammals based on hair microstructure: Methodological adaptations and new morphological patterns

The characterization of patterns of hair microstructure is an important instrument for studying the diet and ecology of mammals, representing an accessible method for identifying predators and their prey. The present study aimed to: (1) describe methodological adaptations developed to optimize traditional guard hair analysis protocols; (2) propose adjustments in the classification of morphological patterns of medulla and cuticle; and (3) establish the microstructural pattern of Brazilian mammals’ hair to assist in the identification of prey and predators in studies based on fecal samples. Hairs from 53 mammal species, including small (n = 16), medium (n = 28) and large size (n = 9), distributed in 24 families and nine orders were analyzed. The orders with the most species analyzed were Carnivora (n = 14), Rodentia (n = 13) and Didelphimorphia (n = 8), while the most representative families were Didelphidae (n = 8), Cricetidae (n = 7) and Felidae (n = 6). Among the species, 13 (24.5% of the total) did not have the microstructural patterns described in studies developed previously in Brazilian territory: Alouatta guariba, Blarinomys breviceps, Bradypus torquatus, Callicebus personatus, Callithrix geoffroyi, Dasyprocta leporina, Hylaeamys seuanezi, Potos flavus, Priodontes maximus, Rhipidomys mastacalis, Sapajus robustus, Sylvilagus minensis and Tayassu pecari. More descriptive nomenclatures were proposed regarding the observed patterns and new patterns were described for species evaluated in previous studies. Our results contribute to the diagnosis of species to be more accurate, contributing to the development of future studies.

Non-volant small mammals (Rodentia and Didelphimorphia) diversity in an isolated area of the Serra da Mantiqueira, Minas Gerais state, Brazil

The southeastern Atlantic Forest of the Zona da Mata Mineira is located in the extreme north of Minas Gerais state, Brazil. The Serra da Mantiqueira, is a mountainous region with a high diversity of small non-volant mammal species, several of which are rare species or endemic lineages. The presence of cryptic species in small mammals makes the karyotype an excellent tool for identification and detection of new lineages. We analyzed the karyotype of 14 species: 11 rodents – Abrawayaomys ruschii, Akodon cursor, Blarinomys breviceps, Delomys sublineatus, Juliomys ossitenuis, Oligoryzomys nigripes, Oligoryzomys flavescens, Oxymycterus dasytrichus, Rhipidomys tribei, Sooretamys angouya, and Thaptomys nigrita; and three marsupials – Monodelphis scalops, Philander quica, and Marmosops incanus. We described for the first time the fundamental autosomal number and the morphology of sex chromosomes of Abrawayaomys ruschii, a rare sigmodontine species, and described a new karyotype for Blarinomys. The revision of published karyotypes of the species herein studied enabled the expansion of the geographic distribution of Oligoryzomys nigripes and Delomys sublineatus.

Intrapopulation karyotypic and cranial characterization of Blarinomys breviceps (Rodentia: Sigmodontinae) from Minas Gerais, Brazil

Despite its wide geographical distribution and habit specialization, Blarinomys breviceps is an understudied species. In this work, we analyzed for the first time the intrapopulation variation of the karyotype and cranial measurements of specimens collected in Minas Gerais state, Brazil. We described three new karyotypes with different diploid numbers due to the presence of B chromosomes (2n = 40, 2n = 41, and 2n = 42, with FN = 50), using conventional staining, GTG- and CBG-banding, Ag-NOR, and FISH with a telomeric probe. In addition, morphometric analyses based on twenty-two quantitative cranial characters showed absence of sexual dimorphism contributing to future studies of geographic variation of the species.

Chromosomal Signatures Corroborate the Phylogenetic Relationships within Akodontini (Rodentia, Sigmodontinae).

Comparative chromosome-painting analysis among highly rearranged karyotypes of Sigmodontinae rodents (Rodentia, Cricetidae) detects conserved syntenic blocks, which are proposed as chromosomal signatures and can be used as phylogenetic markers. In the Akodontini tribe, the molecular topology (Cytb and/or IRBP) shows five low-supported clades (divisions: “Akodon”, “Bibimys”, “Blarinomys”, “Oxymycterus”, and “Scapteromys”) within two high-supported major clades (clade A: “Akodon”, “Bibimys”, and “Oxymycterus”; clade B: “Blarinomys” and “Scapteromys”). Here, we examine the chromosomal signatures of the Akodontini tribe by using Hylaeamys megacephalus (HME) probes to study the karyotypes of Oxymycterus amazonicus (2n = 54, FN = 64) and Blarinomys breviceps (2n = 28, FN = 50), and compare these data with those from other taxa investigated using the same set of probes. We strategically employ the chromosomal signatures to elucidate phylogenetic relationships among the Akodontini. When we follow the evolution of chromosomal signature states, we find that the cytogenetic data corroborate the current molecular relationships in clade A nodes. We discuss the distinct events that caused karyotypic variability in the Oxymycterus and Blarinomys genera. In addition, we propose that Blarinomys may constitute a species complex, and that the taxonomy should be revised to better delimit the geographical boundaries and their taxonomic status.

Small mammals of the Estação Ecológica de Bananal, southeastern Atlantic Forest, Brazil, with description of a new species of Brucepattersonius (Rodentia, Sigmodontinae)

The Atlantic Forest harbors an impressive diversity of nonvolant small mammals. Despite having been the target of many ecological and taxonomical studies in the last decades, this group is still poorly known in several aspects – basic information on intrapopulational morphologic variation and proper diagnoses are lacking for many species, even for common taxa. This is related to the fact that large series of specimens from a single locality are extremely rare in scientific collections. A consistent sampling effort was conducted at Estação Ecológica de Bananal, northeastern São Paulo State, throughout seven field expeditions between 2003 and 2011, under the coordination of the Museu de Zoologia da Universidade de São Paulo, resulting in extensive series of nonvolant small mammals. We studied in detail the external and cranio-dental morphology of this sample (575 specimens), that we assigned to 31 known species besides one new species to science. Most species belong to order Rodentia (26 species) from the families Cricetidae (22 species) and Echimyidae (four species); the remaining (six species) are marsupials from the order Didelphimorphia, family Didelphidae. This is one of the most diverse assemblages ever recorded in this biome, and includes some of the rarest endemic rodents of the Atlantic Forest, such as Abrawayaomys ruschii, Blarinomys breviceps, Drymoreomys albimaculatus, Phaenomys ferrugineus, Phyllomys kerri and Rhagomys rufescens. This outstanding richness can be explained by the extensive sampling effort performed for a long period of time. Also, the capture success of the third expedition (8.25%) is among the highest rates obtained in the Atlantic Forest and the extensive use of pitfall traps was fundamental for trapping this high number of species. Herein, we provide an annotated list of nonvolant small mammals occurring at Estação Ecológica de Bananal, with comprehensive analyses of morphological variation and detailed diagnoses that will allow their proper identification, and will provide a sound basis for a better comprehension of the geographic variation of these taxa across the biome. We also present a formal description for a new species of Brucepattersonius from the mountain ranges along the Paraíba do Sul valley. For five species of sigmodontine rodents, we investigate the levels of ontogenetic and sexual variation, and while the first is accentuate in all analyzed species the second does not contribute significantly to intrapopulation variation.

Helminth metacommunity structure of wild rodents in a preserved area of the Atlantic Forest, Southeast Brazil.

The helminth fauna and metacommunity structure of eight sympatric sigmodontine rodents were investigated at the Serra dos Órgãos National Park, an Atlantic Forest reserve located in the State of Rio de Janeiro, southeast Brazil. Rodents of the species Abrawayaomys ruschii, Akodon montensis, Blarinomys breviceps , Delomys dorsalis, Oligoryzomys flavescens, Oligoryzomys nigripes, Oxymycterus quaestor and Thaptomys nigrita were found infected with helminths. Akodon montensis presented the highest total helminth species richness, with six different species of helminths. The nematode Stilestrongylus lanfrediae was the most abundant and prevalent helminth species observed. The host-parasite network analysis showed little interactions among host species. Akodon montensis seems to act as a keystone-species in the rodent community. This species shared the nematodes Stilestrongylus aculeata with A. ruschii and Protospirura numidica criceticola with T. nigrita, and the cestode Rodentolepis akodontis with D. dorsalis. The congeners host species O. flavescens and O. nigripes shared the nematodes Guerrerostrongylus zetta and S. lanfrediae. The rodents B. breviceps and O. quaestor did not share any helminths with other hosts. The helminth metacommunity showed a random pattern on both infracommunity and component community levels, indicating different responses by each helminth species to the environmental gradient.

Skull morphology of the Brazilian shrew mouse Blarinomys breviceps (Akodontini; Sigmodontinae), with comparative notes on Akodontini rodents

Blarinomys breviceps is a shrew-like mouse, morphologically divergent from the remaining Akodontini (Cricetidae), and best known in the literature for its apparent fossorial adaptations. However, no detailed morphological description concerning its morphology and burrowing habits is available. Through a detailed osteological description and geometric morphometrics approach, we show the distinctiveness of the skull of Blarinomys when compared with other Akodontini. Its unique skull morphology shows some features that can be associated with its underground lifestyle. Many aspects of the peculiar morphology of Blarinomys may be attributed to selective pressures of the underground environment, and are convergent with the morphology of other fossorial rodents. However, in the Neotropics, Blarinomys represents one of the few instances of specialized fossorial habits among members of the Sigmodontinae.

New occurrences and biological aspects to four species of rodents (Mammalia: Cricetidae) from Brazil

The most representative group among mammals are rodents for presenting high ratio to the total of species. However, rodents are considered a "taxonomic chaos" and some species such as Blarinomys breviceps, Bibimys labiosus, Akodon lindberghi and Pseudoryzomys simplex are little known. That can be explained because of low occurrence of small terrestrial mammals in wildlife inventories and/or reduced abundance. The objective is to describe the occurrence of these species and analyze these locations presenting descriptive comments about their biological aspects. Therefore, in addition to specimens collected in the field, some scientific collections were visited and reviews in relevant literature were conducted in order to obtain information about the locations and biological aspects. Akodon lindberghi was found in five sites, Bibimys labiosus was found in 15, Blarinomys breviceps in 39 and Pseudoryzomys simplex in 13. Each species has specific information and they are included in two threatened areas, Atlantic Forest and Cerrado. The occurrences are disconnected and related to taxonomic and methodological problems.Keywords: New records. Rodentia. Sigmodontinae. Occurence area.

Phylogeographic Structure and Karyotypic Diversity of the Brazilian Shrew Mouse (Blarinomys breviceps, Sigmodontinae) in the Atlantic Forest

Blarinomys breviceps possesses cryptic and burrowing habits with poorly documented genetics and life history traits. Due to its rarity, only a few specimens and DNA sequences have been deposited in collections worldwide. Here, we present the most comprehensive cytogenetic and molecular characterization of this rare genus. Phylogenetic analyses based on partial cytochrome b sequences were performed, attempting to establish the relationships among individuals with distinct karyotypes along the geographic distribution of the genus in the Atlantic Forest. Classical and molecular cytogenetics, using banding patterns and FISH of telomeric and whole chromosome X-specific painting probes (obtained from the Akodontini Akodon cursor) were used to characterize and compare the chromosomal complements. Molecular phylogenetic analyses recovered 2 main geographically structured clades, northeastern and southeastern with pairwise sequence divergences among specimens varying between 4.9 and 8.4%. Eight distinct karyomorphs are described: (A) 2n = 52 (50A, XX), (B) 2n = 52 (48A, XY+2Bs), (C) 2n = 45 (42A, XY+1B), (D) 2n = 43 (37A, XX+4Bs), (E) 2n = 37 (34A, XY+1B), (F) 2n = 34 (32A, XX), (G) 2n = 31 (27A, XX+2Bs), (H) 2n = 28 (26A, XY), all with the same number of autosomal arms (FN_A = 50). Variation of 0–4 supernumerary chromosomes (Bs) presenting heterogeneity in morphology and distribution of interstitial telomeric sequences (ITSs) is reported. ITSs are also found in some metacentric autosomes. The phylogeographic separation between 2 major lineages with high levels of genetic divergence, and the wide karyotypic diversity indicate that B. breviceps is a diverse group that warrants taxonomic re-evaluation.

Mammals of Serra da Bocaina National Park, state of Rio de Janeiro, southeastern Brazil

Here we present a commented list of mammals registered in the Serra da Bocaina National Park. Three field trips (February, 2010, and May and July, 2011) were accomplished along the RJ-165 highway in the Municipality of Paraty, State of Rio de Janeiro, Brazil. Forty-eight species belonging to nine orders were recorded. The local mammal fauna could be considered diverse and rich, with some species regarded as biological indicators of habitat quality. Endangered and rare rodent species like Blarinomys breviceps, Juliomys rimofrons, and Thaptomys nigrita were captured. Road and hunting impacts on mammals are discussed.

The karyotype of Blarinomys breviceps (Mammalia: Rodentia: Cricetidae) with comments on its morphology and some ecological notes

The geographic distribution of Blarinomys breviceps (Winge) includes few localities in forested areas in the Atlantic Rainforest from Bahia state in Brazil up to Misiones province in Argentina. Here we add 14 new records for the species in the region of southeastern Brazil. These findings provided information on morphology, natural history and the first karyological data for the species. During two short surveys, one in Santuário da Serra da Concórdia, Valença municipality and another in Fazenda Marimbondo, Mauá municipality, Rio de Janeiro State, Brazil, six specimens were collected in pit fall traps. The specimen trapped in Serra da Concórdia was a sub adult male (age class 3 according to the upper molar row wear). In Fazenda Marimbondo, four adult males and one adult female were captured. Serra da Concórdia is a secondary vegetation in a semideciduous forest type, being a small fragment of 220 ha. The second locality, Fazenda Marimbondo is a high montane forest in an evergreen forest type. Karyotype of the specimen collected in the first locality presented a diploid number of 28 chromosomes and an autosomal number of 50. The specimen collected in Serra da Concórdia was kept alive for seven days. During this period it was fed with live arthropods, what confirms their insectivorous feeding habit, consistent with the molar teeth morphology.

Novo registro de Blarinomys breviceps (Winge, 1888) (Rodentia, Sigmodontinae) no estado de Minas Gerais, Brasil

Blarinomys breviceps is a fossorial rodent, endemic to the Brazilian Atlantic Forest and rarely recorded in small-mammal faunistic inventories. Two male B. breviceps were collected in pit-fall traps in the “Estação de Proteção e Desenvolvimento Ambiental de Peti,” in the municipalities of São Gonçalo do Rio Abaixo and Santa Bárbara, Minas Gerais state, Brazil. This is the first record for this species in the state in 45 years. This finding shows that, although naturally rare, this species is able to inhabit disturbed secondary forests.